diff --git a/Userland/Libraries/LibWeb/Bindings/ExceptionOrUtils.h b/Userland/Libraries/LibWeb/Bindings/ExceptionOrUtils.h
index 3a44f87da8..3f9b5d67ac 100644
--- a/Userland/Libraries/LibWeb/Bindings/ExceptionOrUtils.h
+++ b/Userland/Libraries/LibWeb/Bindings/ExceptionOrUtils.h
@@ -9,7 +9,7 @@
 #include <AK/Optional.h>
 #include <AK/StdLibExtras.h>
 #include <LibJS/Runtime/VM.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::Bindings {
 
@@ -17,7 +17,7 @@ template<typename>
 constexpr bool IsExceptionOr = false;
 
 template<typename T>
-constexpr bool IsExceptionOr<DOM::ExceptionOr<T>> = true;
+constexpr bool IsExceptionOr<WebIDL::ExceptionOr<T>> = true;
 
 template<typename>
 constexpr bool IsThrowCompletionOr = false;
@@ -33,7 +33,7 @@ struct ExtractExceptionOrValueType {
 };
 
 template<typename T>
-struct ExtractExceptionOrValueType<DOM::ExceptionOr<T>> {
+struct ExtractExceptionOrValueType<WebIDL::ExceptionOr<T>> {
     using Type = T;
 };
 
@@ -48,22 +48,22 @@ struct ExtractExceptionOrValueType<void> {
 };
 
 template<>
-struct ExtractExceptionOrValueType<DOM::ExceptionOr<Empty>> {
+struct ExtractExceptionOrValueType<WebIDL::ExceptionOr<Empty>> {
     using Type = JS::Value;
 };
 
 template<>
-struct ExtractExceptionOrValueType<DOM::ExceptionOr<void>> {
+struct ExtractExceptionOrValueType<WebIDL::ExceptionOr<void>> {
     using Type = JS::Value;
 };
 
 ALWAYS_INLINE JS::Completion dom_exception_to_throw_completion(auto&& vm, auto&& exception)
 {
     return exception.visit(
-        [&](DOM::SimpleException const& exception) {
+        [&](WebIDL::SimpleException const& exception) {
             switch (exception.type) {
-#define E(x)                          \
-    case DOM::SimpleExceptionType::x: \
+#define E(x)                             \
+    case WebIDL::SimpleExceptionType::x: \
         return vm.template throw_completion<JS::x>(exception.message);
 
                 ENUMERATE_SIMPLE_WEBIDL_EXCEPTION_TYPES(E)
diff --git a/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.cpp b/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.cpp
index ef44d0fd03..8b835b2da6 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.cpp
@@ -27,7 +27,7 @@ void CSSGroupingRule::visit_edges(Cell::Visitor& visitor)
     visitor.visit(&m_rules);
 }
 
-DOM::ExceptionOr<u32> CSSGroupingRule::insert_rule(StringView rule, u32 index)
+WebIDL::ExceptionOr<u32> CSSGroupingRule::insert_rule(StringView rule, u32 index)
 {
     TRY(m_rules.insert_a_css_rule(rule, index));
     // NOTE: The spec doesn't say where to set the parent rule, so we'll do it here.
@@ -35,7 +35,7 @@ DOM::ExceptionOr<u32> CSSGroupingRule::insert_rule(StringView rule, u32 index)
     return index;
 }
 
-DOM::ExceptionOr<void> CSSGroupingRule::delete_rule(u32 index)
+WebIDL::ExceptionOr<void> CSSGroupingRule::delete_rule(u32 index)
 {
     return m_rules.remove_a_css_rule(index);
 }
diff --git a/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h b/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h
index a4cd691821..9e220e3a8c 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h
@@ -23,8 +23,8 @@ public:
     CSSRuleList const& css_rules() const { return m_rules; }
     CSSRuleList& css_rules() { return m_rules; }
     CSSRuleList* css_rules_for_bindings() { return &m_rules; }
-    DOM::ExceptionOr<u32> insert_rule(StringView rule, u32 index = 0);
-    DOM::ExceptionOr<void> delete_rule(u32 index);
+    WebIDL::ExceptionOr<u32> insert_rule(StringView rule, u32 index = 0);
+    WebIDL::ExceptionOr<void> delete_rule(u32 index);
 
     virtual void for_each_effective_style_rule(Function<void(CSSStyleRule const&)> const& callback) const;
 
diff --git a/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp b/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
index bbd5f35b59..d8da0487a6 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
@@ -48,7 +48,7 @@ bool CSSRuleList::is_supported_property_index(u32 index) const
 }
 
 // https://www.w3.org/TR/cssom/#insert-a-css-rule
-DOM::ExceptionOr<unsigned> CSSRuleList::insert_a_css_rule(Variant<StringView, CSSRule*> rule, u32 index)
+WebIDL::ExceptionOr<unsigned> CSSRuleList::insert_a_css_rule(Variant<StringView, CSSRule*> rule, u32 index)
 {
     // 1. Set length to the number of items in list.
     auto length = m_rules.size();
@@ -86,7 +86,7 @@ DOM::ExceptionOr<unsigned> CSSRuleList::insert_a_css_rule(Variant<StringView, CS
 }
 
 // https://www.w3.org/TR/cssom/#remove-a-css-rule
-DOM::ExceptionOr<void> CSSRuleList::remove_a_css_rule(u32 index)
+WebIDL::ExceptionOr<void> CSSRuleList::remove_a_css_rule(u32 index)
 {
     // 1. Set length to the number of items in list.
     auto length = m_rules.size();
diff --git a/Userland/Libraries/LibWeb/CSS/CSSRuleList.h b/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
index 8e471bb32b..17c9297505 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
@@ -13,8 +13,8 @@
 #include <AK/RefPtr.h>
 #include <LibWeb/Bindings/LegacyPlatformObject.h>
 #include <LibWeb/CSS/CSSRule.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::CSS {
 
@@ -57,8 +57,8 @@ public:
     virtual bool is_supported_property_index(u32 index) const override;
     virtual JS::Value item_value(size_t index) const override;
 
-    DOM::ExceptionOr<void> remove_a_css_rule(u32 index);
-    DOM::ExceptionOr<unsigned> insert_a_css_rule(Variant<StringView, CSSRule*>, u32 index);
+    WebIDL::ExceptionOr<void> remove_a_css_rule(u32 index);
+    WebIDL::ExceptionOr<unsigned> insert_a_css_rule(Variant<StringView, CSSRule*>, u32 index);
 
     void for_each_effective_style_rule(Function<void(CSSStyleRule const&)> const& callback) const;
     // Returns whether the match state of any media queries changed after evaluation.
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.cpp b/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.cpp
index 8620d761af..799218c30d 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.cpp
@@ -69,7 +69,7 @@ Optional<StyleProperty> PropertyOwningCSSStyleDeclaration::property(PropertyID p
 }
 
 // https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-setproperty
-DOM::ExceptionOr<void> PropertyOwningCSSStyleDeclaration::set_property(PropertyID property_id, StringView value, StringView priority)
+WebIDL::ExceptionOr<void> PropertyOwningCSSStyleDeclaration::set_property(PropertyID property_id, StringView value, StringView priority)
 {
     // 1. If the computed flag is set, then throw a NoModificationAllowedError exception.
     // NOTE: This is handled by the virtual override in ResolvedCSSStyleDeclaration.
@@ -117,7 +117,7 @@ DOM::ExceptionOr<void> PropertyOwningCSSStyleDeclaration::set_property(PropertyI
 }
 
 // https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-removeproperty
-DOM::ExceptionOr<String> PropertyOwningCSSStyleDeclaration::remove_property(PropertyID property_id)
+WebIDL::ExceptionOr<String> PropertyOwningCSSStyleDeclaration::remove_property(PropertyID property_id)
 {
     // 1. If the computed flag is set, then throw a NoModificationAllowedError exception.
     // NOTE: This is handled by the virtual override in ResolvedCSSStyleDeclaration.
@@ -214,7 +214,7 @@ String CSSStyleDeclaration::get_property_priority(StringView property_name) cons
     return maybe_property->important == Important::Yes ? "important" : "";
 }
 
-DOM::ExceptionOr<void> CSSStyleDeclaration::set_property(StringView property_name, StringView css_text, StringView priority)
+WebIDL::ExceptionOr<void> CSSStyleDeclaration::set_property(StringView property_name, StringView css_text, StringView priority)
 {
     auto property_id = property_id_from_string(property_name);
     if (property_id == CSS::PropertyID::Invalid)
@@ -222,7 +222,7 @@ DOM::ExceptionOr<void> CSSStyleDeclaration::set_property(StringView property_nam
     return set_property(property_id, css_text, priority);
 }
 
-DOM::ExceptionOr<String> CSSStyleDeclaration::remove_property(StringView property_name)
+WebIDL::ExceptionOr<String> CSSStyleDeclaration::remove_property(StringView property_name)
 {
     auto property_id = property_id_from_string(property_name);
     if (property_id == CSS::PropertyID::Invalid)
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.h b/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.h
index 31c125406a..13dd3f7780 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleDeclaration.h
@@ -36,11 +36,11 @@ public:
 
     virtual Optional<StyleProperty> property(PropertyID) const = 0;
 
-    virtual DOM::ExceptionOr<void> set_property(PropertyID, StringView css_text, StringView priority = ""sv) = 0;
-    virtual DOM::ExceptionOr<String> remove_property(PropertyID) = 0;
+    virtual WebIDL::ExceptionOr<void> set_property(PropertyID, StringView css_text, StringView priority = ""sv) = 0;
+    virtual WebIDL::ExceptionOr<String> remove_property(PropertyID) = 0;
 
-    DOM::ExceptionOr<void> set_property(StringView property_name, StringView css_text, StringView priority);
-    DOM::ExceptionOr<String> remove_property(StringView property_name);
+    WebIDL::ExceptionOr<void> set_property(StringView property_name, StringView css_text, StringView priority);
+    WebIDL::ExceptionOr<String> remove_property(StringView property_name);
 
     String get_property_value(StringView property) const;
     String get_property_priority(StringView property) const;
@@ -72,8 +72,8 @@ public:
 
     virtual Optional<StyleProperty> property(PropertyID) const override;
 
-    virtual DOM::ExceptionOr<void> set_property(PropertyID, StringView css_text, StringView priority) override;
-    virtual DOM::ExceptionOr<String> remove_property(PropertyID) override;
+    virtual WebIDL::ExceptionOr<void> set_property(PropertyID, StringView css_text, StringView priority) override;
+    virtual WebIDL::ExceptionOr<String> remove_property(PropertyID) override;
 
     Vector<StyleProperty> const& properties() const { return m_properties; }
     HashMap<String, StyleProperty> const& custom_properties() const { return m_custom_properties; }
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
index 3ba873d5e5..ef8a525728 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
@@ -8,7 +8,7 @@
 #include <LibWeb/CSS/Parser/Parser.h>
 #include <LibWeb/CSS/StyleSheetList.h>
 #include <LibWeb/DOM/Document.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::CSS {
 
@@ -39,7 +39,7 @@ void CSSStyleSheet::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://www.w3.org/TR/cssom/#dom-cssstylesheet-insertrule
-DOM::ExceptionOr<unsigned> CSSStyleSheet::insert_rule(StringView rule, unsigned index)
+WebIDL::ExceptionOr<unsigned> CSSStyleSheet::insert_rule(StringView rule, unsigned index)
 {
     // FIXME: 1. If the origin-clean flag is unset, throw a SecurityError exception.
 
@@ -71,7 +71,7 @@ DOM::ExceptionOr<unsigned> CSSStyleSheet::insert_rule(StringView rule, unsigned
 }
 
 // https://www.w3.org/TR/cssom/#dom-cssstylesheet-deleterule
-DOM::ExceptionOr<void> CSSStyleSheet::delete_rule(unsigned index)
+WebIDL::ExceptionOr<void> CSSStyleSheet::delete_rule(unsigned index)
 {
     // FIXME: 1. If the origin-clean flag is unset, throw a SecurityError exception.
 
@@ -89,7 +89,7 @@ DOM::ExceptionOr<void> CSSStyleSheet::delete_rule(unsigned index)
 }
 
 // https://www.w3.org/TR/cssom/#dom-cssstylesheet-removerule
-DOM::ExceptionOr<void> CSSStyleSheet::remove_rule(unsigned index)
+WebIDL::ExceptionOr<void> CSSStyleSheet::remove_rule(unsigned index)
 {
     // The removeRule(index) method must run the same steps as deleteRule().
     return delete_rule(index);
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
index 4672921f41..e462789496 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
@@ -40,9 +40,9 @@ public:
     CSSRuleList* css_rules() { return m_rules; }
     CSSRuleList const* css_rules() const { return m_rules; }
 
-    DOM::ExceptionOr<unsigned> insert_rule(StringView rule, unsigned index);
-    DOM::ExceptionOr<void> remove_rule(unsigned index);
-    DOM::ExceptionOr<void> delete_rule(unsigned index);
+    WebIDL::ExceptionOr<unsigned> insert_rule(StringView rule, unsigned index);
+    WebIDL::ExceptionOr<void> remove_rule(unsigned index);
+    WebIDL::ExceptionOr<void> delete_rule(unsigned index);
 
     void for_each_effective_style_rule(Function<void(CSSStyleRule const&)> const& callback) const;
     // Returns whether the match state of any media queries changed after evaluation.
diff --git a/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp b/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
index 62430f7506..61b27774e0 100644
--- a/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
+++ b/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
@@ -535,14 +535,14 @@ Optional<StyleProperty> ResolvedCSSStyleDeclaration::property(PropertyID propert
 }
 
 // https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-setproperty
-DOM::ExceptionOr<void> ResolvedCSSStyleDeclaration::set_property(PropertyID, StringView, StringView)
+WebIDL::ExceptionOr<void> ResolvedCSSStyleDeclaration::set_property(PropertyID, StringView, StringView)
 {
     // 1. If the computed flag is set, then throw a NoModificationAllowedError exception.
     return DOM::NoModificationAllowedError::create(global_object(), "Cannot modify properties in result of getComputedStyle()");
 }
 
 // https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-removeproperty
-DOM::ExceptionOr<String> ResolvedCSSStyleDeclaration::remove_property(PropertyID)
+WebIDL::ExceptionOr<String> ResolvedCSSStyleDeclaration::remove_property(PropertyID)
 {
     // 1. If the computed flag is set, then throw a NoModificationAllowedError exception.
     return DOM::NoModificationAllowedError::create(global_object(), "Cannot remove properties from result of getComputedStyle()");
diff --git a/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.h b/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.h
index f1bd202117..2700f7dd8d 100644
--- a/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.h
+++ b/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.h
@@ -22,8 +22,8 @@ public:
     virtual size_t length() const override;
     virtual String item(size_t index) const override;
     virtual Optional<StyleProperty> property(PropertyID) const override;
-    virtual DOM::ExceptionOr<void> set_property(PropertyID, StringView css_text, StringView priority) override;
-    virtual DOM::ExceptionOr<String> remove_property(PropertyID) override;
+    virtual WebIDL::ExceptionOr<void> set_property(PropertyID, StringView css_text, StringView priority) override;
+    virtual WebIDL::ExceptionOr<String> remove_property(PropertyID) override;
 
     virtual String serialized() const override;
 
diff --git a/Userland/Libraries/LibWeb/Crypto/Crypto.cpp b/Userland/Libraries/LibWeb/Crypto/Crypto.cpp
index f4626ac331..aa35018314 100644
--- a/Userland/Libraries/LibWeb/Crypto/Crypto.cpp
+++ b/Userland/Libraries/LibWeb/Crypto/Crypto.cpp
@@ -39,7 +39,7 @@ JS::NonnullGCPtr<SubtleCrypto> Crypto::subtle() const
 }
 
 // https://w3c.github.io/webcrypto/#dfn-Crypto-method-getRandomValues
-DOM::ExceptionOr<JS::Value> Crypto::get_random_values(JS::Value array) const
+WebIDL::ExceptionOr<JS::Value> Crypto::get_random_values(JS::Value array) const
 {
     // 1. If array is not an Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, or BigUint64Array, then throw a TypeMismatchError and terminate the algorithm.
     if (!array.is_object() || !(is<JS::Int8Array>(array.as_object()) || is<JS::Uint8Array>(array.as_object()) || is<JS::Uint8ClampedArray>(array.as_object()) || is<JS::Int16Array>(array.as_object()) || is<JS::Uint16Array>(array.as_object()) || is<JS::Int32Array>(array.as_object()) || is<JS::Uint32Array>(array.as_object()) || is<JS::BigInt64Array>(array.as_object()) || is<JS::BigUint64Array>(array.as_object())))
diff --git a/Userland/Libraries/LibWeb/Crypto/Crypto.h b/Userland/Libraries/LibWeb/Crypto/Crypto.h
index f7f4a9475d..dececef8b5 100644
--- a/Userland/Libraries/LibWeb/Crypto/Crypto.h
+++ b/Userland/Libraries/LibWeb/Crypto/Crypto.h
@@ -8,7 +8,7 @@
 
 #include <LibWeb/Bindings/PlatformObject.h>
 #include <LibWeb/Crypto/SubtleCrypto.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::Crypto {
 
@@ -22,7 +22,7 @@ public:
 
     JS::NonnullGCPtr<SubtleCrypto> subtle() const;
 
-    DOM::ExceptionOr<JS::Value> get_random_values(JS::Value array) const;
+    WebIDL::ExceptionOr<JS::Value> get_random_values(JS::Value array) const;
     String random_uuid() const;
 
 protected:
diff --git a/Userland/Libraries/LibWeb/DOM/CharacterData.cpp b/Userland/Libraries/LibWeb/DOM/CharacterData.cpp
index 95a40568de..a1344ac18b 100644
--- a/Userland/Libraries/LibWeb/DOM/CharacterData.cpp
+++ b/Userland/Libraries/LibWeb/DOM/CharacterData.cpp
@@ -31,7 +31,7 @@ void CharacterData::set_data(String data)
 }
 
 // https://dom.spec.whatwg.org/#concept-cd-substring
-ExceptionOr<String> CharacterData::substring_data(size_t offset, size_t count) const
+WebIDL::ExceptionOr<String> CharacterData::substring_data(size_t offset, size_t count) const
 {
     // 1. Let length be node’s length.
     auto length = this->length();
@@ -50,7 +50,7 @@ ExceptionOr<String> CharacterData::substring_data(size_t offset, size_t count) c
 }
 
 // https://dom.spec.whatwg.org/#concept-cd-replace
-ExceptionOr<void> CharacterData::replace_data(size_t offset, size_t count, String const& data)
+WebIDL::ExceptionOr<void> CharacterData::replace_data(size_t offset, size_t count, String const& data)
 {
     // 1. Let length be node’s length.
     auto length = this->length();
@@ -109,21 +109,21 @@ ExceptionOr<void> CharacterData::replace_data(size_t offset, size_t count, Strin
 }
 
 // https://dom.spec.whatwg.org/#dom-characterdata-appenddata
-ExceptionOr<void> CharacterData::append_data(String const& data)
+WebIDL::ExceptionOr<void> CharacterData::append_data(String const& data)
 {
     // The appendData(data) method steps are to replace data with node this, offset this’s length, count 0, and data data.
     return replace_data(m_data.length(), 0, data);
 }
 
 // https://dom.spec.whatwg.org/#dom-characterdata-insertdata
-ExceptionOr<void> CharacterData::insert_data(size_t offset, String const& data)
+WebIDL::ExceptionOr<void> CharacterData::insert_data(size_t offset, String const& data)
 {
     // The insertData(offset, data) method steps are to replace data with node this, offset offset, count 0, and data data.
     return replace_data(offset, 0, data);
 }
 
 // https://dom.spec.whatwg.org/#dom-characterdata-deletedata
-ExceptionOr<void> CharacterData::delete_data(size_t offset, size_t count)
+WebIDL::ExceptionOr<void> CharacterData::delete_data(size_t offset, size_t count)
 {
     // The deleteData(offset, count) method steps are to replace data with node this, offset offset, count count, and data the empty string.
     return replace_data(offset, count, String::empty());
diff --git a/Userland/Libraries/LibWeb/DOM/CharacterData.h b/Userland/Libraries/LibWeb/DOM/CharacterData.h
index b57e1ebf21..a97ecad4b0 100644
--- a/Userland/Libraries/LibWeb/DOM/CharacterData.h
+++ b/Userland/Libraries/LibWeb/DOM/CharacterData.h
@@ -27,11 +27,11 @@ public:
 
     unsigned length() const { return m_data.length(); }
 
-    ExceptionOr<String> substring_data(size_t offset, size_t count) const;
-    ExceptionOr<void> append_data(String const&);
-    ExceptionOr<void> insert_data(size_t offset, String const&);
-    ExceptionOr<void> delete_data(size_t offset, size_t count);
-    ExceptionOr<void> replace_data(size_t offset, size_t count, String const&);
+    WebIDL::ExceptionOr<String> substring_data(size_t offset, size_t count) const;
+    WebIDL::ExceptionOr<void> append_data(String const&);
+    WebIDL::ExceptionOr<void> insert_data(size_t offset, String const&);
+    WebIDL::ExceptionOr<void> delete_data(size_t offset, size_t count);
+    WebIDL::ExceptionOr<void> replace_data(size_t offset, size_t count, String const&);
 
 protected:
     explicit CharacterData(Document&, NodeType, String const&);
diff --git a/Userland/Libraries/LibWeb/DOM/ChildNode.h b/Userland/Libraries/LibWeb/DOM/ChildNode.h
index ca7b48ae1d..4a54f7d518 100644
--- a/Userland/Libraries/LibWeb/DOM/ChildNode.h
+++ b/Userland/Libraries/LibWeb/DOM/ChildNode.h
@@ -6,8 +6,8 @@
 
 #pragma once
 
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/NodeOperations.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -16,7 +16,7 @@ template<typename NodeType>
 class ChildNode {
 public:
     // https://dom.spec.whatwg.org/#dom-childnode-before
-    ExceptionOr<void> before(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
+    WebIDL::ExceptionOr<void> before(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
     {
         auto* node = static_cast<NodeType*>(this);
 
@@ -46,7 +46,7 @@ public:
     }
 
     // https://dom.spec.whatwg.org/#dom-childnode-after
-    ExceptionOr<void> after(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
+    WebIDL::ExceptionOr<void> after(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
     {
         auto* node = static_cast<NodeType*>(this);
 
@@ -70,7 +70,7 @@ public:
     }
 
     // https://dom.spec.whatwg.org/#dom-childnode-replacewith
-    ExceptionOr<void> replace_with(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
+    WebIDL::ExceptionOr<void> replace_with(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
     {
         auto* node = static_cast<NodeType*>(this);
 
diff --git a/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp b/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
index d1cb97ff5e..69da598dcd 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
+++ b/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
@@ -38,7 +38,7 @@ void DOMImplementation::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://dom.spec.whatwg.org/#dom-domimplementation-createdocument
-ExceptionOr<JS::NonnullGCPtr<Document>> DOMImplementation::create_document(String const& namespace_, String const& qualified_name, JS::GCPtr<DocumentType> doctype) const
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> DOMImplementation::create_document(String const& namespace_, String const& qualified_name, JS::GCPtr<DocumentType> doctype) const
 {
     // FIXME: This should specifically be an XML document.
     auto xml_document = Document::create(Bindings::main_thread_internal_window_object());
@@ -103,7 +103,7 @@ JS::NonnullGCPtr<Document> DOMImplementation::create_html_document(String const&
 }
 
 // https://dom.spec.whatwg.org/#dom-domimplementation-createdocumenttype
-ExceptionOr<JS::NonnullGCPtr<DocumentType>> DOMImplementation::create_document_type(String const& qualified_name, String const& public_id, String const& system_id)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentType>> DOMImplementation::create_document_type(String const& qualified_name, String const& public_id, String const& system_id)
 {
     TRY(Document::validate_qualified_name(global_object(), qualified_name));
     auto document_type = DocumentType::create(document());
diff --git a/Userland/Libraries/LibWeb/DOM/DOMImplementation.h b/Userland/Libraries/LibWeb/DOM/DOMImplementation.h
index 3aac381a78..b4776c727b 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMImplementation.h
+++ b/Userland/Libraries/LibWeb/DOM/DOMImplementation.h
@@ -20,9 +20,9 @@ public:
     static JS::NonnullGCPtr<DOMImplementation> create(Document&);
     virtual ~DOMImplementation();
 
-    ExceptionOr<JS::NonnullGCPtr<Document>> create_document(String const&, String const&, JS::GCPtr<DocumentType>) const;
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> create_document(String const&, String const&, JS::GCPtr<DocumentType>) const;
     JS::NonnullGCPtr<Document> create_html_document(String const& title) const;
-    ExceptionOr<JS::NonnullGCPtr<DocumentType>> create_document_type(String const& qualified_name, String const& public_id, String const& system_id);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentType>> create_document_type(String const& qualified_name, String const& public_id, String const& system_id);
 
     // https://dom.spec.whatwg.org/#dom-domimplementation-hasfeature
     bool has_feature() const { return true; }
diff --git a/Userland/Libraries/LibWeb/DOM/DOMTokenList.cpp b/Userland/Libraries/LibWeb/DOM/DOMTokenList.cpp
index 82ef51ed99..f448000e9c 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMTokenList.cpp
+++ b/Userland/Libraries/LibWeb/DOM/DOMTokenList.cpp
@@ -108,7 +108,7 @@ bool DOMTokenList::contains(StringView token)
 }
 
 // https://dom.spec.whatwg.org/#dom-domtokenlist-add
-ExceptionOr<void> DOMTokenList::add(Vector<String> const& tokens)
+WebIDL::ExceptionOr<void> DOMTokenList::add(Vector<String> const& tokens)
 {
     // 1. For each token in tokens:
     for (auto const& token : tokens) {
@@ -126,7 +126,7 @@ ExceptionOr<void> DOMTokenList::add(Vector<String> const& tokens)
 }
 
 // https://dom.spec.whatwg.org/#dom-domtokenlist-remove
-ExceptionOr<void> DOMTokenList::remove(Vector<String> const& tokens)
+WebIDL::ExceptionOr<void> DOMTokenList::remove(Vector<String> const& tokens)
 {
     // 1. For each token in tokens:
     for (auto const& token : tokens) {
@@ -144,7 +144,7 @@ ExceptionOr<void> DOMTokenList::remove(Vector<String> const& tokens)
 }
 
 // https://dom.spec.whatwg.org/#dom-domtokenlist-toggle
-ExceptionOr<bool> DOMTokenList::toggle(String const& token, Optional<bool> force)
+WebIDL::ExceptionOr<bool> DOMTokenList::toggle(String const& token, Optional<bool> force)
 {
     // 1. If token is the empty string, then throw a "SyntaxError" DOMException.
     // 2. If token contains any ASCII whitespace, then throw an "InvalidCharacterError" DOMException.
@@ -175,7 +175,7 @@ ExceptionOr<bool> DOMTokenList::toggle(String const& token, Optional<bool> force
 }
 
 // https://dom.spec.whatwg.org/#dom-domtokenlist-replace
-ExceptionOr<bool> DOMTokenList::replace(String const& token, String const& new_token)
+WebIDL::ExceptionOr<bool> DOMTokenList::replace(String const& token, String const& new_token)
 {
     // 1. If either token or newToken is the empty string, then throw a "SyntaxError" DOMException.
     // 2. If either token or newToken contains any ASCII whitespace, then throw an "InvalidCharacterError" DOMException.
@@ -198,13 +198,13 @@ ExceptionOr<bool> DOMTokenList::replace(String const& token, String const& new_t
 
 // https://dom.spec.whatwg.org/#dom-domtokenlist-supports
 // https://dom.spec.whatwg.org/#concept-domtokenlist-validation
-ExceptionOr<bool> DOMTokenList::supports([[maybe_unused]] StringView token)
+WebIDL::ExceptionOr<bool> DOMTokenList::supports([[maybe_unused]] StringView token)
 {
     // FIXME: Implement this fully when any use case defines supported tokens.
 
     // 1. If the associated attribute’s local name does not define supported tokens, throw a TypeError.
-    return DOM::SimpleException {
-        DOM::SimpleExceptionType::TypeError,
+    return WebIDL::SimpleException {
+        WebIDL::SimpleExceptionType::TypeError,
         String::formatted("Attribute {} does not define any supported tokens", m_associated_attribute)
     };
 
@@ -231,7 +231,7 @@ void DOMTokenList::set_value(String value)
     associated_element->set_attribute(m_associated_attribute, move(value));
 }
 
-ExceptionOr<void> DOMTokenList::validate_token(StringView token) const
+WebIDL::ExceptionOr<void> DOMTokenList::validate_token(StringView token) const
 {
     if (token.is_empty())
         return SyntaxError::create(global_object(), "Non-empty DOM tokens are not allowed");
diff --git a/Userland/Libraries/LibWeb/DOM/DOMTokenList.h b/Userland/Libraries/LibWeb/DOM/DOMTokenList.h
index 4197a7697a..b281e7e2ec 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMTokenList.h
+++ b/Userland/Libraries/LibWeb/DOM/DOMTokenList.h
@@ -13,8 +13,8 @@
 #include <AK/StringView.h>
 #include <AK/Vector.h>
 #include <LibWeb/Bindings/LegacyPlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -34,18 +34,18 @@ public:
     size_t length() const { return m_token_set.size(); }
     String const& item(size_t index) const;
     bool contains(StringView token);
-    ExceptionOr<void> add(Vector<String> const& tokens);
-    ExceptionOr<void> remove(Vector<String> const& tokens);
-    ExceptionOr<bool> toggle(String const& token, Optional<bool> force);
-    ExceptionOr<bool> replace(String const& token, String const& new_token);
-    ExceptionOr<bool> supports(StringView token);
+    WebIDL::ExceptionOr<void> add(Vector<String> const& tokens);
+    WebIDL::ExceptionOr<void> remove(Vector<String> const& tokens);
+    WebIDL::ExceptionOr<bool> toggle(String const& token, Optional<bool> force);
+    WebIDL::ExceptionOr<bool> replace(String const& token, String const& new_token);
+    WebIDL::ExceptionOr<bool> supports(StringView token);
     String value() const;
     void set_value(String value);
 
 private:
     DOMTokenList(Element const& associated_element, FlyString associated_attribute);
 
-    ExceptionOr<void> validate_token(StringView token) const;
+    WebIDL::ExceptionOr<void> validate_token(StringView token) const;
     void run_update_steps();
 
     WeakPtr<Element> m_associated_element;
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index 6c383f7959..398675eef6 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -28,7 +28,6 @@
 #include <LibWeb/DOM/Element.h>
 #include <LibWeb/DOM/ElementFactory.h>
 #include <LibWeb/DOM/Event.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/HTMLCollection.h>
 #include <LibWeb/DOM/NodeIterator.h>
 #include <LibWeb/DOM/Range.h>
@@ -73,6 +72,7 @@
 #include <LibWeb/UIEvents/FocusEvent.h>
 #include <LibWeb/UIEvents/KeyboardEvent.h>
 #include <LibWeb/UIEvents/MouseEvent.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -351,7 +351,7 @@ void Document::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-document-write
-ExceptionOr<void> Document::write(Vector<String> const& strings)
+WebIDL::ExceptionOr<void> Document::write(Vector<String> const& strings)
 {
     StringBuilder builder;
     builder.join(""sv, strings);
@@ -360,7 +360,7 @@ ExceptionOr<void> Document::write(Vector<String> const& strings)
 }
 
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-document-writeln
-ExceptionOr<void> Document::writeln(Vector<String> const& strings)
+WebIDL::ExceptionOr<void> Document::writeln(Vector<String> const& strings)
 {
     StringBuilder builder;
     builder.join(""sv, strings);
@@ -370,7 +370,7 @@ ExceptionOr<void> Document::writeln(Vector<String> const& strings)
 }
 
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#document-write-steps
-ExceptionOr<void> Document::run_the_document_write_steps(String input)
+WebIDL::ExceptionOr<void> Document::run_the_document_write_steps(String input)
 {
     // 1. If document is an XML document, then throw an "InvalidStateError" DOMException.
     if (m_type == Type::XML)
@@ -405,7 +405,7 @@ ExceptionOr<void> Document::run_the_document_write_steps(String input)
 }
 
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-document-open
-ExceptionOr<Document*> Document::open(String const&, String const&)
+WebIDL::ExceptionOr<Document*> Document::open(String const&, String const&)
 {
     // 1. If document is an XML document, then throw an "InvalidStateError" DOMException exception.
     if (m_type == Type::XML)
@@ -476,7 +476,7 @@ ExceptionOr<Document*> Document::open(String const&, String const&)
 }
 
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#closing-the-input-stream
-ExceptionOr<void> Document::close()
+WebIDL::ExceptionOr<void> Document::close()
 {
     // 1. If document is an XML document, then throw an "InvalidStateError" DOMException exception.
     if (m_type == Type::XML)
@@ -585,7 +585,7 @@ HTML::HTMLElement* Document::body()
 }
 
 // https://html.spec.whatwg.org/multipage/dom.html#dom-document-body
-ExceptionOr<void> Document::set_body(HTML::HTMLElement* new_body)
+WebIDL::ExceptionOr<void> Document::set_body(HTML::HTMLElement* new_body)
 {
     if (!is<HTML::HTMLBodyElement>(new_body) && !is<HTML::HTMLFrameSetElement>(new_body))
         return DOM::HierarchyRequestError::create(global_object(), "Invalid document body element, must be 'body' or 'frameset'");
@@ -1108,7 +1108,7 @@ JS::Value Document::run_javascript(StringView source, StringView filename)
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createelement
-DOM::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element(FlyString const& a_local_name)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element(FlyString const& a_local_name)
 {
     auto local_name = a_local_name;
 
@@ -1135,7 +1135,7 @@ DOM::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element(FlyString c
 // https://dom.spec.whatwg.org/#dom-document-createelementns
 // https://dom.spec.whatwg.org/#internal-createelementns-steps
 // FIXME: This only implements step 4 of the algorithm and does not take in options.
-DOM::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element_ns(String const& namespace_, String const& qualified_name)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element_ns(String const& namespace_, String const& qualified_name)
 {
     // 1. Let namespace, prefix, and localName be the result of passing namespace and qualifiedName to validate and extract.
     auto extracted_qualified_name = TRY(validate_and_extract(global_object(), namespace_, qualified_name));
@@ -1168,7 +1168,7 @@ JS::NonnullGCPtr<Range> Document::create_range()
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createevent
-DOM::ExceptionOr<JS::NonnullGCPtr<Event>> Document::create_event(String const& interface)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> Document::create_event(String const& interface)
 {
     auto& window_object = window();
 
@@ -1285,7 +1285,7 @@ Vector<JS::Handle<HTML::HTMLScriptElement>> Document::take_scripts_to_execute_in
 }
 
 // https://dom.spec.whatwg.org/#dom-document-importnode
-ExceptionOr<JS::NonnullGCPtr<Node>> Document::import_node(JS::NonnullGCPtr<Node> node, bool deep)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Document::import_node(JS::NonnullGCPtr<Node> node, bool deep)
 {
     // 1. If node is a document or shadow root, then throw a "NotSupportedError" DOMException.
     if (is<Document>(*node) || is<ShadowRoot>(*node))
@@ -1333,7 +1333,7 @@ void Document::adopt_node(Node& node)
 }
 
 // https://dom.spec.whatwg.org/#dom-document-adoptnode
-ExceptionOr<JS::NonnullGCPtr<Node>> Document::adopt_node_binding(JS::NonnullGCPtr<Node> node)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Document::adopt_node_binding(JS::NonnullGCPtr<Node> node)
 {
     if (is<Document>(*node))
         return DOM::NotSupportedError::create(global_object(), "Cannot adopt a document into a document");
@@ -1798,7 +1798,7 @@ bool Document::is_valid_name(String const& name)
 }
 
 // https://dom.spec.whatwg.org/#validate
-ExceptionOr<Document::PrefixAndTagName> Document::validate_qualified_name(JS::Object& global_object, String const& qualified_name)
+WebIDL::ExceptionOr<Document::PrefixAndTagName> Document::validate_qualified_name(JS::Object& global_object, String const& qualified_name)
 {
     if (qualified_name.is_empty())
         return InvalidCharacterError::create(global_object, "Empty string is not a valid qualified name.");
diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index 337690e629..5969a115ca 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -21,7 +21,6 @@
 #include <LibWeb/CSS/StyleComputer.h>
 #include <LibWeb/CSS/StyleSheetList.h>
 #include <LibWeb/Cookie/Cookie.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/NonElementParentNode.h>
 #include <LibWeb/DOM/ParentNode.h>
 #include <LibWeb/HTML/CrossOrigin/CrossOriginOpenerPolicy.h>
@@ -33,6 +32,7 @@
 #include <LibWeb/HTML/Scripting/Environments.h>
 #include <LibWeb/HTML/VisibilityState.h>
 #include <LibWeb/HTML/Window.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -156,7 +156,7 @@ public:
         return const_cast<Document*>(this)->body();
     }
 
-    ExceptionOr<void> set_body(HTML::HTMLElement* new_body);
+    WebIDL::ExceptionOr<void> set_body(HTML::HTMLElement* new_body);
 
     String title() const;
     void set_title(String const&);
@@ -219,12 +219,12 @@ public:
 
     JS::Value run_javascript(StringView source, StringView filename = "(unknown)"sv);
 
-    ExceptionOr<JS::NonnullGCPtr<Element>> create_element(FlyString const& local_name);
-    ExceptionOr<JS::NonnullGCPtr<Element>> create_element_ns(String const& namespace_, String const& qualified_name);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element(FlyString const& local_name);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element_ns(String const& namespace_, String const& qualified_name);
     JS::NonnullGCPtr<DocumentFragment> create_document_fragment();
     JS::NonnullGCPtr<Text> create_text_node(String const& data);
     JS::NonnullGCPtr<Comment> create_comment(String const& data);
-    ExceptionOr<JS::NonnullGCPtr<Event>> create_event(String const& interface);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> create_event(String const& interface);
     JS::NonnullGCPtr<Range> create_range();
 
     void set_pending_parsing_blocking_script(Badge<HTML::HTMLScriptElement>, HTML::HTMLScriptElement*);
@@ -253,9 +253,9 @@ public:
     // https://dom.spec.whatwg.org/#xml-document
     bool is_xml_document() const { return m_type == Type::XML; }
 
-    ExceptionOr<JS::NonnullGCPtr<Node>> import_node(JS::NonnullGCPtr<Node> node, bool deep);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> import_node(JS::NonnullGCPtr<Node> node, bool deep);
     void adopt_node(Node&);
-    ExceptionOr<JS::NonnullGCPtr<Node>> adopt_node_binding(JS::NonnullGCPtr<Node>);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> adopt_node_binding(JS::NonnullGCPtr<Node>);
 
     DocumentType const* doctype() const;
     String const& compat_mode() const;
@@ -286,11 +286,11 @@ public:
 
     void set_window(Badge<HTML::BrowsingContext>, HTML::Window&);
 
-    ExceptionOr<void> write(Vector<String> const& strings);
-    ExceptionOr<void> writeln(Vector<String> const& strings);
+    WebIDL::ExceptionOr<void> write(Vector<String> const& strings);
+    WebIDL::ExceptionOr<void> writeln(Vector<String> const& strings);
 
-    ExceptionOr<Document*> open(String const& = "", String const& = "");
-    ExceptionOr<void> close();
+    WebIDL::ExceptionOr<Document*> open(String const& = "", String const& = "");
+    WebIDL::ExceptionOr<void> close();
 
     HTML::Window* default_view() { return m_window.ptr(); }
 
@@ -367,7 +367,7 @@ public:
         FlyString prefix;
         FlyString tag_name;
     };
-    static ExceptionOr<PrefixAndTagName> validate_qualified_name(JS::Object& global_object, String const& qualified_name);
+    static WebIDL::ExceptionOr<PrefixAndTagName> validate_qualified_name(JS::Object& global_object, String const& qualified_name);
 
     JS::NonnullGCPtr<NodeIterator> create_node_iterator(Node& root, unsigned what_to_show, JS::GCPtr<NodeFilter>);
     JS::NonnullGCPtr<TreeWalker> create_tree_walker(Node& root, unsigned what_to_show, JS::GCPtr<NodeFilter>);
@@ -449,7 +449,7 @@ private:
 
     void evaluate_media_rules();
 
-    ExceptionOr<void> run_the_document_write_steps(String);
+    WebIDL::ExceptionOr<void> run_the_document_write_steps(String);
 
     size_t m_next_layout_node_serial_id { 0 };
 
diff --git a/Userland/Libraries/LibWeb/DOM/Element.cpp b/Userland/Libraries/LibWeb/DOM/Element.cpp
index 5920b32ed8..14d2c5ef37 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Element.cpp
@@ -16,7 +16,6 @@
 #include <LibWeb/DOM/DOMTokenList.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Element.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/HTMLCollection.h>
 #include <LibWeb/DOM/ShadowRoot.h>
 #include <LibWeb/DOM/Text.h>
@@ -39,6 +38,7 @@
 #include <LibWeb/Layout/TreeBuilder.h>
 #include <LibWeb/Namespace.h>
 #include <LibWeb/Painting/PaintableBox.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -82,7 +82,7 @@ String Element::get_attribute(FlyString const& name) const
 }
 
 // https://dom.spec.whatwg.org/#dom-element-setattribute
-ExceptionOr<void> Element::set_attribute(FlyString const& name, String const& value)
+WebIDL::ExceptionOr<void> Element::set_attribute(FlyString const& name, String const& value)
 {
     // 1. If qualifiedName does not match the Name production in XML, then throw an "InvalidCharacterError" DOMException.
     // FIXME: Proper name validation
@@ -118,7 +118,7 @@ ExceptionOr<void> Element::set_attribute(FlyString const& name, String const& va
 }
 
 // https://dom.spec.whatwg.org/#validate-and-extract
-ExceptionOr<QualifiedName> validate_and_extract(JS::Object& global_object, FlyString namespace_, FlyString qualified_name)
+WebIDL::ExceptionOr<QualifiedName> validate_and_extract(JS::Object& global_object, FlyString namespace_, FlyString qualified_name)
 {
     // 1. If namespace is the empty string, then set it to null.
     if (namespace_.is_empty())
@@ -161,7 +161,7 @@ ExceptionOr<QualifiedName> validate_and_extract(JS::Object& global_object, FlySt
 }
 
 // https://dom.spec.whatwg.org/#dom-element-setattributens
-ExceptionOr<void> Element::set_attribute_ns(FlyString const& namespace_, FlyString const& qualified_name, String const& value)
+WebIDL::ExceptionOr<void> Element::set_attribute_ns(FlyString const& namespace_, FlyString const& qualified_name, String const& value)
 {
     // 1. Let namespace, prefix, and localName be the result of passing namespace and qualifiedName to validate and extract.
     auto extracted_qualified_name = TRY(validate_and_extract(global_object(), namespace_, qualified_name));
@@ -190,7 +190,7 @@ bool Element::has_attribute(FlyString const& name) const
 }
 
 // https://dom.spec.whatwg.org/#dom-element-toggleattribute
-DOM::ExceptionOr<bool> Element::toggle_attribute(FlyString const& name, Optional<bool> force)
+WebIDL::ExceptionOr<bool> Element::toggle_attribute(FlyString const& name, Optional<bool> force)
 {
     // 1. If qualifiedName does not match the Name production in XML, then throw an "InvalidCharacterError" DOMException.
     // FIXME: Proper name validation
@@ -439,7 +439,7 @@ DOMTokenList* Element::class_list()
 }
 
 // https://dom.spec.whatwg.org/#dom-element-matches
-DOM::ExceptionOr<bool> Element::matches(StringView selectors) const
+WebIDL::ExceptionOr<bool> Element::matches(StringView selectors) const
 {
     auto maybe_selectors = parse_selector(CSS::Parser::ParsingContext(static_cast<ParentNode&>(const_cast<Element&>(*this))), selectors);
     if (!maybe_selectors.has_value())
@@ -454,7 +454,7 @@ DOM::ExceptionOr<bool> Element::matches(StringView selectors) const
 }
 
 // https://dom.spec.whatwg.org/#dom-element-closest
-DOM::ExceptionOr<DOM::Element const*> Element::closest(StringView selectors) const
+WebIDL::ExceptionOr<DOM::Element const*> Element::closest(StringView selectors) const
 {
     auto maybe_selectors = parse_selector(CSS::Parser::ParsingContext(static_cast<ParentNode&>(const_cast<Element&>(*this))), selectors);
     if (!maybe_selectors.has_value())
@@ -479,7 +479,7 @@ DOM::ExceptionOr<DOM::Element const*> Element::closest(StringView selectors) con
     return nullptr;
 }
 
-ExceptionOr<void> Element::set_inner_html(String const& markup)
+WebIDL::ExceptionOr<void> Element::set_inner_html(String const& markup)
 {
     TRY(DOMParsing::inner_html_setter(*this, markup));
 
@@ -729,7 +729,7 @@ void Element::serialize_pseudo_elements_as_json(JsonArraySerializer<StringBuilde
 }
 
 // https://w3c.github.io/DOM-Parsing/#dom-element-insertadjacenthtml
-DOM::ExceptionOr<void> Element::insert_adjacent_html(String position, String text)
+WebIDL::ExceptionOr<void> Element::insert_adjacent_html(String position, String text)
 {
     JS::GCPtr<Node> context;
     // 1. Use the first matching item from this list:
diff --git a/Userland/Libraries/LibWeb/DOM/Element.h b/Userland/Libraries/LibWeb/DOM/Element.h
index 203f3fc50d..d7d77f2c4e 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.h
+++ b/Userland/Libraries/LibWeb/DOM/Element.h
@@ -12,7 +12,6 @@
 #include <LibWeb/CSS/StyleComputer.h>
 #include <LibWeb/DOM/Attr.h>
 #include <LibWeb/DOM/ChildNode.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/NamedNodeMap.h>
 #include <LibWeb/DOM/NonDocumentTypeChildNode.h>
 #include <LibWeb/DOM/ParentNode.h>
@@ -22,6 +21,7 @@
 #include <LibWeb/HTML/TagNames.h>
 #include <LibWeb/Layout/Node.h>
 #include <LibWeb/Layout/TreeBuilder.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -52,18 +52,18 @@ public:
     bool has_attributes() const { return !m_attributes->is_empty(); }
     String attribute(FlyString const& name) const { return get_attribute(name); }
     String get_attribute(FlyString const& name) const;
-    ExceptionOr<void> set_attribute(FlyString const& name, String const& value);
-    ExceptionOr<void> set_attribute_ns(FlyString const& namespace_, FlyString const& qualified_name, String const& value);
+    WebIDL::ExceptionOr<void> set_attribute(FlyString const& name, String const& value);
+    WebIDL::ExceptionOr<void> set_attribute_ns(FlyString const& namespace_, FlyString const& qualified_name, String const& value);
     void remove_attribute(FlyString const& name);
-    DOM::ExceptionOr<bool> toggle_attribute(FlyString const& name, Optional<bool> force);
+    WebIDL::ExceptionOr<bool> toggle_attribute(FlyString const& name, Optional<bool> force);
     size_t attribute_list_size() const { return m_attributes->length(); }
     NamedNodeMap const* attributes() const { return m_attributes.ptr(); }
     Vector<String> get_attribute_names() const;
 
     DOMTokenList* class_list();
 
-    DOM::ExceptionOr<bool> matches(StringView selectors) const;
-    DOM::ExceptionOr<DOM::Element const*> closest(StringView selectors) const;
+    WebIDL::ExceptionOr<bool> matches(StringView selectors) const;
+    WebIDL::ExceptionOr<DOM::Element const*> closest(StringView selectors) const;
 
     int client_top() const;
     int client_left() const;
@@ -106,9 +106,9 @@ public:
     CSS::CSSStyleDeclaration* style_for_bindings();
 
     String inner_html() const;
-    ExceptionOr<void> set_inner_html(String const&);
+    WebIDL::ExceptionOr<void> set_inner_html(String const&);
 
-    ExceptionOr<void> insert_adjacent_html(String position, String text);
+    WebIDL::ExceptionOr<void> insert_adjacent_html(String position, String text);
 
     bool is_focused() const;
     bool is_active() const;
@@ -172,6 +172,6 @@ private:
 template<>
 inline bool Node::fast_is<Element>() const { return is_element(); }
 
-ExceptionOr<QualifiedName> validate_and_extract(JS::Object& global_object, FlyString namespace_, FlyString qualified_name);
+WebIDL::ExceptionOr<QualifiedName> validate_and_extract(JS::Object& global_object, FlyString namespace_, FlyString qualified_name);
 
 }
diff --git a/Userland/Libraries/LibWeb/DOM/EventTarget.cpp b/Userland/Libraries/LibWeb/DOM/EventTarget.cpp
index 50ecabbbb4..796015167d 100644
--- a/Userland/Libraries/LibWeb/DOM/EventTarget.cpp
+++ b/Userland/Libraries/LibWeb/DOM/EventTarget.cpp
@@ -223,7 +223,7 @@ void EventTarget::remove_from_event_listener_list(DOMEventListener& listener)
 }
 
 // https://dom.spec.whatwg.org/#dom-eventtarget-dispatchevent
-ExceptionOr<bool> EventTarget::dispatch_event_binding(Event& event)
+WebIDL::ExceptionOr<bool> EventTarget::dispatch_event_binding(Event& event)
 {
     // 1. If event’s dispatch flag is set, or if its initialized flag is not set, then throw an "InvalidStateError" DOMException.
     if (event.dispatched())
diff --git a/Userland/Libraries/LibWeb/DOM/EventTarget.h b/Userland/Libraries/LibWeb/DOM/EventTarget.h
index 28c1bb18ad..63afbfd6e2 100644
--- a/Userland/Libraries/LibWeb/DOM/EventTarget.h
+++ b/Userland/Libraries/LibWeb/DOM/EventTarget.h
@@ -12,9 +12,9 @@
 #include <LibJS/Forward.h>
 #include <LibWeb/Bindings/PlatformObject.h>
 #include <LibWeb/DOM/DOMEventListener.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
 #include <LibWeb/HTML/EventHandler.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -34,7 +34,7 @@ public:
     void remove_event_listener_without_options(FlyString const& type, IDLEventListener& callback);
 
     virtual bool dispatch_event(Event&);
-    ExceptionOr<bool> dispatch_event_binding(Event&);
+    WebIDL::ExceptionOr<bool> dispatch_event_binding(Event&);
 
     virtual EventTarget* get_parent(Event const&) { return nullptr; }
 
diff --git a/Userland/Libraries/LibWeb/DOM/MutationObserver.cpp b/Userland/Libraries/LibWeb/DOM/MutationObserver.cpp
index 3d9520b5c0..3c5bd4f5ca 100644
--- a/Userland/Libraries/LibWeb/DOM/MutationObserver.cpp
+++ b/Userland/Libraries/LibWeb/DOM/MutationObserver.cpp
@@ -41,7 +41,7 @@ void MutationObserver::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://dom.spec.whatwg.org/#dom-mutationobserver-observe
-ExceptionOr<void> MutationObserver::observe(Node& target, MutationObserverInit options)
+WebIDL::ExceptionOr<void> MutationObserver::observe(Node& target, MutationObserverInit options)
 {
     // 1. If either options["attributeOldValue"] or options["attributeFilter"] exists, and options["attributes"] does not exist, then set options["attributes"] to true.
     if ((options.attribute_old_value.has_value() || options.attribute_filter.has_value()) && !options.attributes.has_value())
@@ -53,22 +53,22 @@ ExceptionOr<void> MutationObserver::observe(Node& target, MutationObserverInit o
 
     // 3. If none of options["childList"], options["attributes"], and options["characterData"] is true, then throw a TypeError.
     if (!options.child_list && (!options.attributes.has_value() || !options.attributes.value()) && (!options.character_data.has_value() || !options.character_data.value()))
-        return SimpleException { SimpleExceptionType::TypeError, "Options must have one of childList, attributes or characterData set to true." };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Options must have one of childList, attributes or characterData set to true." };
 
     // 4. If options["attributeOldValue"] is true and options["attributes"] is false, then throw a TypeError.
     // NOTE: If attributeOldValue is present, attributes will be present because of step 1.
     if (options.attribute_old_value.has_value() && options.attribute_old_value.value() && !options.attributes.value())
-        return SimpleException { SimpleExceptionType::TypeError, "attributes must be true if attributeOldValue is true." };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "attributes must be true if attributeOldValue is true." };
 
     // 5. If options["attributeFilter"] is present and options["attributes"] is false, then throw a TypeError.
     // NOTE: If attributeFilter is present, attributes will be present because of step 1.
     if (options.attribute_filter.has_value() && !options.attributes.value())
-        return SimpleException { SimpleExceptionType::TypeError, "attributes must be true if attributeFilter is present." };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "attributes must be true if attributeFilter is present." };
 
     // 6. If options["characterDataOldValue"] is true and options["characterData"] is false, then throw a TypeError.
     // NOTE: If characterDataOldValue is present, characterData will be present because of step 2.
     if (options.character_data_old_value.has_value() && options.character_data_old_value.value() && !options.character_data.value())
-        return SimpleException { SimpleExceptionType::TypeError, "characterData must be true if characterDataOldValue is true." };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "characterData must be true if characterDataOldValue is true." };
 
     // 7. For each registered of target’s registered observer list, if registered’s observer is this:
     bool updated_existing_observer = false;
diff --git a/Userland/Libraries/LibWeb/DOM/MutationObserver.h b/Userland/Libraries/LibWeb/DOM/MutationObserver.h
index 33437ed35f..b6f86d7b61 100644
--- a/Userland/Libraries/LibWeb/DOM/MutationObserver.h
+++ b/Userland/Libraries/LibWeb/DOM/MutationObserver.h
@@ -10,9 +10,9 @@
 #include <AK/NonnullRefPtrVector.h>
 #include <AK/RefCounted.h>
 #include <LibJS/Heap/Handle.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/MutationRecord.h>
 #include <LibWeb/WebIDL/CallbackType.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -35,7 +35,7 @@ public:
     static JS::NonnullGCPtr<MutationObserver> create_with_global_object(HTML::Window&, JS::GCPtr<WebIDL::CallbackType>);
     virtual ~MutationObserver() override;
 
-    ExceptionOr<void> observe(Node& target, MutationObserverInit options = {});
+    WebIDL::ExceptionOr<void> observe(Node& target, MutationObserverInit options = {});
     void disconnect();
     Vector<JS::Handle<MutationRecord>> take_records();
 
diff --git a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
index 5241902184..07260e6475 100644
--- a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
+++ b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
@@ -80,13 +80,13 @@ Attr const* NamedNodeMap::get_named_item(StringView qualified_name) const
 }
 
 // https://dom.spec.whatwg.org/#dom-namednodemap-setnameditem
-ExceptionOr<Attr const*> NamedNodeMap::set_named_item(Attr& attribute)
+WebIDL::ExceptionOr<Attr const*> NamedNodeMap::set_named_item(Attr& attribute)
 {
     return set_attribute(attribute);
 }
 
 // https://dom.spec.whatwg.org/#dom-namednodemap-removenameditem
-ExceptionOr<Attr const*> NamedNodeMap::remove_named_item(StringView qualified_name)
+WebIDL::ExceptionOr<Attr const*> NamedNodeMap::remove_named_item(StringView qualified_name)
 {
     // 1. Let attr be the result of removing an attribute given qualifiedName and element.
     auto const* attribute = remove_attribute(qualified_name);
@@ -133,7 +133,7 @@ Attr const* NamedNodeMap::get_attribute(StringView qualified_name, size_t* item_
 }
 
 // https://dom.spec.whatwg.org/#concept-element-attributes-set
-ExceptionOr<Attr const*> NamedNodeMap::set_attribute(Attr& attribute)
+WebIDL::ExceptionOr<Attr const*> NamedNodeMap::set_attribute(Attr& attribute)
 {
     // 1. If attr’s element is neither null nor element, throw an "InUseAttributeError" DOMException.
     if ((attribute.owner_element() != nullptr) && (attribute.owner_element() != &associated_element()))
diff --git a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
index d4487b61f4..89b1c422c2 100644
--- a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
+++ b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
@@ -11,8 +11,8 @@
 #include <AK/String.h>
 #include <AK/StringView.h>
 #include <LibWeb/Bindings/LegacyPlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -35,13 +35,13 @@ public:
     // Methods defined by the spec for JavaScript:
     Attr const* item(u32 index) const;
     Attr const* get_named_item(StringView qualified_name) const;
-    ExceptionOr<Attr const*> set_named_item(Attr& attribute);
-    ExceptionOr<Attr const*> remove_named_item(StringView qualified_name);
+    WebIDL::ExceptionOr<Attr const*> set_named_item(Attr& attribute);
+    WebIDL::ExceptionOr<Attr const*> remove_named_item(StringView qualified_name);
 
     // Methods defined by the spec for internal use:
     Attr* get_attribute(StringView qualified_name, size_t* item_index = nullptr);
     Attr const* get_attribute(StringView qualified_name, size_t* item_index = nullptr) const;
-    ExceptionOr<Attr const*> set_attribute(Attr& attribute);
+    WebIDL::ExceptionOr<Attr const*> set_attribute(Attr& attribute);
     void replace_attribute(Attr& old_attribute, Attr& new_attribute, size_t old_attribute_index);
     void append_attribute(Attr& attribute);
     Attr const* remove_attribute(StringView qualified_name);
diff --git a/Userland/Libraries/LibWeb/DOM/Node.cpp b/Userland/Libraries/LibWeb/DOM/Node.cpp
index eac22f3f31..b2d171d2ab 100644
--- a/Userland/Libraries/LibWeb/DOM/Node.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Node.cpp
@@ -311,7 +311,7 @@ Element const* Node::parent_element() const
 }
 
 // https://dom.spec.whatwg.org/#concept-node-ensure-pre-insertion-validity
-ExceptionOr<void> Node::ensure_pre_insertion_validity(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child) const
+WebIDL::ExceptionOr<void> Node::ensure_pre_insertion_validity(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child) const
 {
     // 1. If parent is not a Document, DocumentFragment, or Element node, then throw a "HierarchyRequestError" DOMException.
     if (!is<Document>(this) && !is<DocumentFragment>(this) && !is<Element>(this))
@@ -456,7 +456,7 @@ void Node::insert_before(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child, boo
 }
 
 // https://dom.spec.whatwg.org/#concept-node-pre-insert
-ExceptionOr<JS::NonnullGCPtr<Node>> Node::pre_insert(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Node::pre_insert(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child)
 {
     // 1. Ensure pre-insertion validity of node into parent before child.
     TRY(ensure_pre_insertion_validity(node, child));
@@ -476,14 +476,14 @@ ExceptionOr<JS::NonnullGCPtr<Node>> Node::pre_insert(JS::NonnullGCPtr<Node> node
 }
 
 // https://dom.spec.whatwg.org/#dom-node-removechild
-ExceptionOr<JS::NonnullGCPtr<Node>> Node::remove_child(JS::NonnullGCPtr<Node> child)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Node::remove_child(JS::NonnullGCPtr<Node> child)
 {
     // The removeChild(child) method steps are to return the result of pre-removing child from this.
     return pre_remove(child);
 }
 
 // https://dom.spec.whatwg.org/#concept-node-pre-remove
-ExceptionOr<JS::NonnullGCPtr<Node>> Node::pre_remove(JS::NonnullGCPtr<Node> child)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Node::pre_remove(JS::NonnullGCPtr<Node> child)
 {
     // 1. If child’s parent is not parent, then throw a "NotFoundError" DOMException.
     if (child->parent() != this)
@@ -497,7 +497,7 @@ ExceptionOr<JS::NonnullGCPtr<Node>> Node::pre_remove(JS::NonnullGCPtr<Node> chil
 }
 
 // https://dom.spec.whatwg.org/#concept-node-append
-ExceptionOr<JS::NonnullGCPtr<Node>> Node::append_child(JS::NonnullGCPtr<Node> node)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Node::append_child(JS::NonnullGCPtr<Node> node)
 {
     // To append a node to a parent, pre-insert node into parent before null.
     return pre_insert(node, nullptr);
@@ -608,7 +608,7 @@ void Node::remove(bool suppress_observers)
 }
 
 // https://dom.spec.whatwg.org/#concept-node-replace
-ExceptionOr<JS::NonnullGCPtr<Node>> Node::replace_child(JS::NonnullGCPtr<Node> node, JS::NonnullGCPtr<Node> child)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Node::replace_child(JS::NonnullGCPtr<Node> node, JS::NonnullGCPtr<Node> child)
 {
     // If parent is not a Document, DocumentFragment, or Element node, then throw a "HierarchyRequestError" DOMException.
     if (!is<Document>(this) && !is<DocumentFragment>(this) && !is<Element>(this))
@@ -792,7 +792,7 @@ JS::NonnullGCPtr<Node> Node::clone_node(Document* document, bool clone_children)
 }
 
 // https://dom.spec.whatwg.org/#dom-node-clonenode
-ExceptionOr<JS::NonnullGCPtr<Node>> Node::clone_node_binding(bool deep)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> Node::clone_node_binding(bool deep)
 {
     // 1. If this is a shadow root, then throw a "NotSupportedError" DOMException.
     if (is<ShadowRoot>(*this))
diff --git a/Userland/Libraries/LibWeb/DOM/Node.h b/Userland/Libraries/LibWeb/DOM/Node.h
index 3a754a182b..16b627039b 100644
--- a/Userland/Libraries/LibWeb/DOM/Node.h
+++ b/Userland/Libraries/LibWeb/DOM/Node.h
@@ -13,7 +13,7 @@
 #include <AK/TypeCasts.h>
 #include <AK/Vector.h>
 #include <LibWeb/DOM/EventTarget.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -81,21 +81,21 @@ public:
     virtual bool is_html_template_element() const { return false; }
     virtual bool is_browsing_context_container() const { return false; }
 
-    ExceptionOr<JS::NonnullGCPtr<Node>> pre_insert(JS::NonnullGCPtr<Node>, JS::GCPtr<Node>);
-    ExceptionOr<JS::NonnullGCPtr<Node>> pre_remove(JS::NonnullGCPtr<Node>);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> pre_insert(JS::NonnullGCPtr<Node>, JS::GCPtr<Node>);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> pre_remove(JS::NonnullGCPtr<Node>);
 
-    ExceptionOr<JS::NonnullGCPtr<Node>> append_child(JS::NonnullGCPtr<Node>);
-    ExceptionOr<JS::NonnullGCPtr<Node>> remove_child(JS::NonnullGCPtr<Node>);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> append_child(JS::NonnullGCPtr<Node>);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> remove_child(JS::NonnullGCPtr<Node>);
 
     void insert_before(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child, bool suppress_observers = false);
     void remove(bool suppress_observers = false);
     void remove_all_children(bool suppress_observers = false);
     u16 compare_document_position(JS::GCPtr<Node> other);
 
-    ExceptionOr<JS::NonnullGCPtr<Node>> replace_child(JS::NonnullGCPtr<Node> node, JS::NonnullGCPtr<Node> child);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> replace_child(JS::NonnullGCPtr<Node> node, JS::NonnullGCPtr<Node> child);
 
     JS::NonnullGCPtr<Node> clone_node(Document* document = nullptr, bool clone_children = false);
-    ExceptionOr<JS::NonnullGCPtr<Node>> clone_node_binding(bool deep);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> clone_node_binding(bool deep);
 
     // NOTE: This is intended for the JS bindings.
     bool has_child_nodes() const { return has_children(); }
@@ -177,7 +177,7 @@ public:
     template<typename T>
     bool fast_is() const = delete;
 
-    ExceptionOr<void> ensure_pre_insertion_validity(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child) const;
+    WebIDL::ExceptionOr<void> ensure_pre_insertion_validity(JS::NonnullGCPtr<Node> node, JS::GCPtr<Node> child) const;
 
     bool is_host_including_inclusive_ancestor_of(Node const&) const;
 
diff --git a/Userland/Libraries/LibWeb/DOM/NodeOperations.cpp b/Userland/Libraries/LibWeb/DOM/NodeOperations.cpp
index 0f36843943..04b3501945 100644
--- a/Userland/Libraries/LibWeb/DOM/NodeOperations.cpp
+++ b/Userland/Libraries/LibWeb/DOM/NodeOperations.cpp
@@ -14,7 +14,7 @@
 namespace Web::DOM {
 
 // https://dom.spec.whatwg.org/#converting-nodes-into-a-node
-ExceptionOr<JS::NonnullGCPtr<Node>> convert_nodes_to_single_node(Vector<Variant<JS::Handle<Node>, String>> const& nodes, DOM::Document& document)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> convert_nodes_to_single_node(Vector<Variant<JS::Handle<Node>, String>> const& nodes, DOM::Document& document)
 {
     // 1. Let node be null.
     // 2. Replace each string in nodes with a new Text node whose data is the string and node document is document.
diff --git a/Userland/Libraries/LibWeb/DOM/NodeOperations.h b/Userland/Libraries/LibWeb/DOM/NodeOperations.h
index fe9817e58e..275ec316f3 100644
--- a/Userland/Libraries/LibWeb/DOM/NodeOperations.h
+++ b/Userland/Libraries/LibWeb/DOM/NodeOperations.h
@@ -12,6 +12,6 @@
 
 namespace Web::DOM {
 
-ExceptionOr<JS::NonnullGCPtr<Node>> convert_nodes_to_single_node(Vector<Variant<JS::Handle<Node>, String>> const& nodes, DOM::Document& document);
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Node>> convert_nodes_to_single_node(Vector<Variant<JS::Handle<Node>, String>> const& nodes, DOM::Document& document);
 
 }
diff --git a/Userland/Libraries/LibWeb/DOM/ParentNode.cpp b/Userland/Libraries/LibWeb/DOM/ParentNode.cpp
index 80bb214151..a388db88c1 100644
--- a/Userland/Libraries/LibWeb/DOM/ParentNode.cpp
+++ b/Userland/Libraries/LibWeb/DOM/ParentNode.cpp
@@ -18,7 +18,7 @@
 
 namespace Web::DOM {
 
-ExceptionOr<JS::GCPtr<Element>> ParentNode::query_selector(StringView selector_text)
+WebIDL::ExceptionOr<JS::GCPtr<Element>> ParentNode::query_selector(StringView selector_text)
 {
     auto maybe_selectors = parse_selector(CSS::Parser::ParsingContext(*this), selector_text);
     if (!maybe_selectors.has_value())
@@ -41,7 +41,7 @@ ExceptionOr<JS::GCPtr<Element>> ParentNode::query_selector(StringView selector_t
     return result;
 }
 
-ExceptionOr<JS::NonnullGCPtr<NodeList>> ParentNode::query_selector_all(StringView selector_text)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<NodeList>> ParentNode::query_selector_all(StringView selector_text)
 {
     auto maybe_selectors = parse_selector(CSS::Parser::ParsingContext(*this), selector_text);
     if (!maybe_selectors.has_value())
@@ -168,7 +168,7 @@ JS::NonnullGCPtr<HTMLCollection> ParentNode::get_elements_by_tag_name_ns(FlyStri
 }
 
 // https://dom.spec.whatwg.org/#dom-parentnode-prepend
-ExceptionOr<void> ParentNode::prepend(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
+WebIDL::ExceptionOr<void> ParentNode::prepend(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
 {
     // 1. Let node be the result of converting nodes into a node given nodes and this’s node document.
     auto node = TRY(convert_nodes_to_single_node(nodes, document()));
@@ -179,7 +179,7 @@ ExceptionOr<void> ParentNode::prepend(Vector<Variant<JS::Handle<Node>, String>>
     return {};
 }
 
-ExceptionOr<void> ParentNode::append(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
+WebIDL::ExceptionOr<void> ParentNode::append(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
 {
     // 1. Let node be the result of converting nodes into a node given nodes and this’s node document.
     auto node = TRY(convert_nodes_to_single_node(nodes, document()));
@@ -190,7 +190,7 @@ ExceptionOr<void> ParentNode::append(Vector<Variant<JS::Handle<Node>, String>> c
     return {};
 }
 
-ExceptionOr<void> ParentNode::replace_children(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
+WebIDL::ExceptionOr<void> ParentNode::replace_children(Vector<Variant<JS::Handle<Node>, String>> const& nodes)
 {
     // 1. Let node be the result of converting nodes into a node given nodes and this’s node document.
     auto node = TRY(convert_nodes_to_single_node(nodes, document()));
diff --git a/Userland/Libraries/LibWeb/DOM/ParentNode.h b/Userland/Libraries/LibWeb/DOM/ParentNode.h
index 276e710d18..99b8bda747 100644
--- a/Userland/Libraries/LibWeb/DOM/ParentNode.h
+++ b/Userland/Libraries/LibWeb/DOM/ParentNode.h
@@ -23,17 +23,17 @@ public:
     JS::GCPtr<Element> last_element_child();
     u32 child_element_count() const;
 
-    ExceptionOr<JS::GCPtr<Element>> query_selector(StringView);
-    ExceptionOr<JS::NonnullGCPtr<NodeList>> query_selector_all(StringView);
+    WebIDL::ExceptionOr<JS::GCPtr<Element>> query_selector(StringView);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<NodeList>> query_selector_all(StringView);
 
     JS::NonnullGCPtr<HTMLCollection> children();
 
     JS::NonnullGCPtr<HTMLCollection> get_elements_by_tag_name(FlyString const&);
     JS::NonnullGCPtr<HTMLCollection> get_elements_by_tag_name_ns(FlyString const&, FlyString const&);
 
-    ExceptionOr<void> prepend(Vector<Variant<JS::Handle<Node>, String>> const& nodes);
-    ExceptionOr<void> append(Vector<Variant<JS::Handle<Node>, String>> const& nodes);
-    ExceptionOr<void> replace_children(Vector<Variant<JS::Handle<Node>, String>> const& nodes);
+    WebIDL::ExceptionOr<void> prepend(Vector<Variant<JS::Handle<Node>, String>> const& nodes);
+    WebIDL::ExceptionOr<void> append(Vector<Variant<JS::Handle<Node>, String>> const& nodes);
+    WebIDL::ExceptionOr<void> replace_children(Vector<Variant<JS::Handle<Node>, String>> const& nodes);
 
 protected:
     ParentNode(JS::Realm& realm, Document& document, NodeType type)
diff --git a/Userland/Libraries/LibWeb/DOM/Range.cpp b/Userland/Libraries/LibWeb/DOM/Range.cpp
index c44ab7c25c..3853c92699 100644
--- a/Userland/Libraries/LibWeb/DOM/Range.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Range.cpp
@@ -131,7 +131,7 @@ static RelativeBoundaryPointPosition position_of_boundary_point_relative_to_othe
     return RelativeBoundaryPointPosition::Before;
 }
 
-ExceptionOr<void> Range::set_start_or_end(Node& node, u32 offset, StartOrEnd start_or_end)
+WebIDL::ExceptionOr<void> Range::set_start_or_end(Node& node, u32 offset, StartOrEnd start_or_end)
 {
     // To set the start or end of a range to a boundary point (node, offset), run these steps:
 
@@ -176,20 +176,20 @@ ExceptionOr<void> Range::set_start_or_end(Node& node, u32 offset, StartOrEnd sta
 }
 
 // https://dom.spec.whatwg.org/#concept-range-bp-set
-ExceptionOr<void> Range::set_start(Node& node, u32 offset)
+WebIDL::ExceptionOr<void> Range::set_start(Node& node, u32 offset)
 {
     // The setStart(node, offset) method steps are to set the start of this to boundary point (node, offset).
     return set_start_or_end(node, offset, StartOrEnd::Start);
 }
 
-ExceptionOr<void> Range::set_end(Node& node, u32 offset)
+WebIDL::ExceptionOr<void> Range::set_end(Node& node, u32 offset)
 {
     // The setEnd(node, offset) method steps are to set the end of this to boundary point (node, offset).
     return set_start_or_end(node, offset, StartOrEnd::End);
 }
 
 // https://dom.spec.whatwg.org/#dom-range-setstartbefore
-ExceptionOr<void> Range::set_start_before(Node& node)
+WebIDL::ExceptionOr<void> Range::set_start_before(Node& node)
 {
     // 1. Let parent be node’s parent.
     auto* parent = node.parent();
@@ -203,7 +203,7 @@ ExceptionOr<void> Range::set_start_before(Node& node)
 }
 
 // https://dom.spec.whatwg.org/#dom-range-setstartafter
-ExceptionOr<void> Range::set_start_after(Node& node)
+WebIDL::ExceptionOr<void> Range::set_start_after(Node& node)
 {
     // 1. Let parent be node’s parent.
     auto* parent = node.parent();
@@ -217,7 +217,7 @@ ExceptionOr<void> Range::set_start_after(Node& node)
 }
 
 // https://dom.spec.whatwg.org/#dom-range-setendbefore
-ExceptionOr<void> Range::set_end_before(Node& node)
+WebIDL::ExceptionOr<void> Range::set_end_before(Node& node)
 {
     // 1. Let parent be node’s parent.
     auto* parent = node.parent();
@@ -231,7 +231,7 @@ ExceptionOr<void> Range::set_end_before(Node& node)
 }
 
 // https://dom.spec.whatwg.org/#dom-range-setendafter
-ExceptionOr<void> Range::set_end_after(Node& node)
+WebIDL::ExceptionOr<void> Range::set_end_after(Node& node)
 {
     // 1. Let parent be node’s parent.
     auto* parent = node.parent();
@@ -245,7 +245,7 @@ ExceptionOr<void> Range::set_end_after(Node& node)
 }
 
 // https://dom.spec.whatwg.org/#dom-range-compareboundarypoints
-ExceptionOr<i16> Range::compare_boundary_points(u16 how, Range const& source_range) const
+WebIDL::ExceptionOr<i16> Range::compare_boundary_points(u16 how, Range const& source_range) const
 {
     // 1. If how is not one of
     //      - START_TO_START,
@@ -332,7 +332,7 @@ ExceptionOr<i16> Range::compare_boundary_points(u16 how, Range const& source_ran
 }
 
 // https://dom.spec.whatwg.org/#concept-range-select
-ExceptionOr<void> Range::select(Node& node)
+WebIDL::ExceptionOr<void> Range::select(Node& node)
 {
     // 1. Let parent be node’s parent.
     auto* parent = node.parent();
@@ -356,7 +356,7 @@ ExceptionOr<void> Range::select(Node& node)
 }
 
 // https://dom.spec.whatwg.org/#dom-range-selectnode
-ExceptionOr<void> Range::select_node(Node& node)
+WebIDL::ExceptionOr<void> Range::select_node(Node& node)
 {
     // The selectNode(node) method steps are to select node within this.
     return select(node);
@@ -377,7 +377,7 @@ void Range::collapse(bool to_start)
 }
 
 // https://dom.spec.whatwg.org/#dom-range-selectnodecontents
-ExceptionOr<void> Range::select_node_contents(Node const& node)
+WebIDL::ExceptionOr<void> Range::select_node_contents(Node const& node)
 {
     // 1. If node is a doctype, throw an "InvalidNodeTypeError" DOMException.
     if (is<DocumentType>(node))
@@ -466,7 +466,7 @@ bool Range::intersects_node(Node const& node) const
 }
 
 // https://dom.spec.whatwg.org/#dom-range-ispointinrange
-ExceptionOr<bool> Range::is_point_in_range(Node const& node, u32 offset) const
+WebIDL::ExceptionOr<bool> Range::is_point_in_range(Node const& node, u32 offset) const
 {
     // 1. If node’s root is different from this’s root, return false.
     if (&node.root() != &root())
@@ -491,7 +491,7 @@ ExceptionOr<bool> Range::is_point_in_range(Node const& node, u32 offset) const
 }
 
 // https://dom.spec.whatwg.org/#dom-range-comparepoint
-ExceptionOr<i16> Range::compare_point(Node const& node, u32 offset) const
+WebIDL::ExceptionOr<i16> Range::compare_point(Node const& node, u32 offset) const
 {
     // 1. If node’s root is different from this’s root, then throw a "WrongDocumentError" DOMException.
     if (&node.root() != &root())
@@ -549,13 +549,13 @@ String Range::to_string() const
 }
 
 // https://dom.spec.whatwg.org/#dom-range-extractcontents
-ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::extract_contents()
+WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::extract_contents()
 {
     return extract();
 }
 
 // https://dom.spec.whatwg.org/#concept-range-extract
-ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::extract()
+WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::extract()
 {
     // 1. Let fragment be a new DocumentFragment node whose node document is range’s start node’s node document.
     auto* fragment = heap().allocate<DOM::DocumentFragment>(realm(), const_cast<Document&>(start_container()->document()));
@@ -771,13 +771,13 @@ bool Range::partially_contains_node(Node const& node) const
 }
 
 // https://dom.spec.whatwg.org/#dom-range-insertnode
-ExceptionOr<void> Range::insert_node(JS::NonnullGCPtr<Node> node)
+WebIDL::ExceptionOr<void> Range::insert_node(JS::NonnullGCPtr<Node> node)
 {
     return insert(node);
 }
 
 // https://dom.spec.whatwg.org/#concept-range-insert
-ExceptionOr<void> Range::insert(JS::NonnullGCPtr<Node> node)
+WebIDL::ExceptionOr<void> Range::insert(JS::NonnullGCPtr<Node> node)
 {
     // 1. If range’s start node is a ProcessingInstruction or Comment node, is a Text node whose parent is null, or is node, then throw a "HierarchyRequestError" DOMException.
     if ((is<ProcessingInstruction>(*m_start_container) || is<Comment>(*m_start_container))
@@ -844,7 +844,7 @@ ExceptionOr<void> Range::insert(JS::NonnullGCPtr<Node> node)
 }
 
 // https://dom.spec.whatwg.org/#dom-range-surroundcontents
-ExceptionOr<void> Range::surround_contents(JS::NonnullGCPtr<Node> new_parent)
+WebIDL::ExceptionOr<void> Range::surround_contents(JS::NonnullGCPtr<Node> new_parent)
 {
     // 1. If a non-Text node is partially contained in this, then throw an "InvalidStateError" DOMException.
     Node* start_non_text_node = start_container();
@@ -878,13 +878,13 @@ ExceptionOr<void> Range::surround_contents(JS::NonnullGCPtr<Node> new_parent)
 }
 
 // https://dom.spec.whatwg.org/#dom-range-clonecontents
-ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::clone_contents()
+WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::clone_contents()
 {
     return clone_the_contents();
 }
 
 // https://dom.spec.whatwg.org/#concept-range-clone
-ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::clone_the_contents()
+WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::clone_the_contents()
 {
     // 1. Let fragment be a new DocumentFragment node whose node document is range’s start node’s node document.
     auto* fragment = heap().allocate<DOM::DocumentFragment>(realm(), const_cast<Document&>(start_container()->document()));
@@ -1040,7 +1040,7 @@ ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> Range::clone_the_contents()
 }
 
 // https://dom.spec.whatwg.org/#dom-range-deletecontents
-ExceptionOr<void> Range::delete_contents()
+WebIDL::ExceptionOr<void> Range::delete_contents()
 {
     // 1. If this is collapsed, then return.
     if (collapsed())
diff --git a/Userland/Libraries/LibWeb/DOM/Range.h b/Userland/Libraries/LibWeb/DOM/Range.h
index fadc1dfc71..234c2bb810 100644
--- a/Userland/Libraries/LibWeb/DOM/Range.h
+++ b/Userland/Libraries/LibWeb/DOM/Range.h
@@ -27,15 +27,15 @@ public:
 
     // FIXME: There are a ton of methods missing here.
 
-    ExceptionOr<void> set_start(Node& node, u32 offset);
-    ExceptionOr<void> set_end(Node& node, u32 offset);
-    ExceptionOr<void> set_start_before(Node& node);
-    ExceptionOr<void> set_start_after(Node& node);
-    ExceptionOr<void> set_end_before(Node& node);
-    ExceptionOr<void> set_end_after(Node& node);
-    ExceptionOr<void> select_node(Node& node);
+    WebIDL::ExceptionOr<void> set_start(Node& node, u32 offset);
+    WebIDL::ExceptionOr<void> set_end(Node& node, u32 offset);
+    WebIDL::ExceptionOr<void> set_start_before(Node& node);
+    WebIDL::ExceptionOr<void> set_start_after(Node& node);
+    WebIDL::ExceptionOr<void> set_end_before(Node& node);
+    WebIDL::ExceptionOr<void> set_end_after(Node& node);
+    WebIDL::ExceptionOr<void> select_node(Node& node);
     void collapse(bool to_start);
-    ExceptionOr<void> select_node_contents(Node const&);
+    WebIDL::ExceptionOr<void> select_node_contents(Node const&);
 
     // https://dom.spec.whatwg.org/#dom-range-start_to_start
     enum HowToCompareBoundaryPoints : u16 {
@@ -45,7 +45,7 @@ public:
         END_TO_START = 3,
     };
 
-    ExceptionOr<i16> compare_boundary_points(u16 how, Range const& source_range) const;
+    WebIDL::ExceptionOr<i16> compare_boundary_points(u16 how, Range const& source_range) const;
 
     JS::NonnullGCPtr<Range> inverted() const;
     JS::NonnullGCPtr<Range> normalized() const;
@@ -61,15 +61,15 @@ public:
     }
 
     bool intersects_node(Node const&) const;
-    ExceptionOr<bool> is_point_in_range(Node const&, u32 offset) const;
-    ExceptionOr<i16> compare_point(Node const&, u32 offset) const;
+    WebIDL::ExceptionOr<bool> is_point_in_range(Node const&, u32 offset) const;
+    WebIDL::ExceptionOr<i16> compare_point(Node const&, u32 offset) const;
 
-    ExceptionOr<void> delete_contents();
-    ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> extract_contents();
-    ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> clone_contents();
+    WebIDL::ExceptionOr<void> delete_contents();
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> extract_contents();
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> clone_contents();
 
-    ExceptionOr<void> insert_node(JS::NonnullGCPtr<Node>);
-    ExceptionOr<void> surround_contents(JS::NonnullGCPtr<Node> new_parent);
+    WebIDL::ExceptionOr<void> insert_node(JS::NonnullGCPtr<Node>);
+    WebIDL::ExceptionOr<void> surround_contents(JS::NonnullGCPtr<Node> new_parent);
 
     String to_string() const;
 
@@ -84,12 +84,12 @@ private:
         End,
     };
 
-    ExceptionOr<void> set_start_or_end(Node& node, u32 offset, StartOrEnd start_or_end);
-    ExceptionOr<void> select(Node& node);
+    WebIDL::ExceptionOr<void> set_start_or_end(Node& node, u32 offset, StartOrEnd start_or_end);
+    WebIDL::ExceptionOr<void> select(Node& node);
 
-    ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> extract();
-    ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> clone_the_contents();
-    ExceptionOr<void> insert(JS::NonnullGCPtr<Node>);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> extract();
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<DocumentFragment>> clone_the_contents();
+    WebIDL::ExceptionOr<void> insert(JS::NonnullGCPtr<Node>);
 
     bool contains_node(Node const&) const;
     bool partially_contains_node(Node const&) const;
diff --git a/Userland/Libraries/LibWeb/DOM/ShadowRoot.cpp b/Userland/Libraries/LibWeb/DOM/ShadowRoot.cpp
index 01a312ee65..19ba81c54f 100644
--- a/Userland/Libraries/LibWeb/DOM/ShadowRoot.cpp
+++ b/Userland/Libraries/LibWeb/DOM/ShadowRoot.cpp
@@ -37,7 +37,7 @@ String ShadowRoot::inner_html() const
 }
 
 // https://w3c.github.io/DOM-Parsing/#dom-innerhtml-innerhtml
-ExceptionOr<void> ShadowRoot::set_inner_html(String const& markup)
+WebIDL::ExceptionOr<void> ShadowRoot::set_inner_html(String const& markup)
 {
     TRY(DOMParsing::inner_html_setter(*this, markup));
 
diff --git a/Userland/Libraries/LibWeb/DOM/ShadowRoot.h b/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
index 800307c8b8..f15fe502fc 100644
--- a/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
+++ b/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
@@ -29,7 +29,7 @@ public:
     String mode() const { return m_closed ? "closed" : "open"; }
 
     String inner_html() const;
-    ExceptionOr<void> set_inner_html(String const&);
+    WebIDL::ExceptionOr<void> set_inner_html(String const&);
 
 private:
     ShadowRoot(Document&, Element&);
diff --git a/Userland/Libraries/LibWeb/DOM/StaticRange.cpp b/Userland/Libraries/LibWeb/DOM/StaticRange.cpp
index f5adac85ef..332007fda9 100644
--- a/Userland/Libraries/LibWeb/DOM/StaticRange.cpp
+++ b/Userland/Libraries/LibWeb/DOM/StaticRange.cpp
@@ -9,8 +9,8 @@
 #include <LibWeb/DOM/Attr.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/DocumentType.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/StaticRange.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
 
@@ -23,7 +23,7 @@ StaticRange::StaticRange(Node& start_container, u32 start_offset, Node& end_cont
 StaticRange::~StaticRange() = default;
 
 // https://dom.spec.whatwg.org/#dom-staticrange-staticrange
-ExceptionOr<StaticRange*> StaticRange::create_with_global_object(HTML::Window& window, StaticRangeInit& init)
+WebIDL::ExceptionOr<StaticRange*> StaticRange::create_with_global_object(HTML::Window& window, StaticRangeInit& init)
 {
     // 1. If init["startContainer"] or init["endContainer"] is a DocumentType or Attr node, then throw an "InvalidNodeTypeError" DOMException.
     if (is<DocumentType>(*init.start_container) || is<Attr>(*init.start_container))
diff --git a/Userland/Libraries/LibWeb/DOM/StaticRange.h b/Userland/Libraries/LibWeb/DOM/StaticRange.h
index 95546d7fea..ec98ba31b0 100644
--- a/Userland/Libraries/LibWeb/DOM/StaticRange.h
+++ b/Userland/Libraries/LibWeb/DOM/StaticRange.h
@@ -24,7 +24,7 @@ class StaticRange final : public AbstractRange {
     WEB_PLATFORM_OBJECT(StaticRange, JS::Object);
 
 public:
-    static ExceptionOr<StaticRange*> create_with_global_object(HTML::Window&, StaticRangeInit& init);
+    static WebIDL::ExceptionOr<StaticRange*> create_with_global_object(HTML::Window&, StaticRangeInit& init);
 
     StaticRange(Node& start_container, u32 start_offset, Node& end_container, u32 end_offset);
     virtual ~StaticRange() override;
diff --git a/Userland/Libraries/LibWeb/DOM/Text.cpp b/Userland/Libraries/LibWeb/DOM/Text.cpp
index 57398559e1..65bae6668e 100644
--- a/Userland/Libraries/LibWeb/DOM/Text.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Text.cpp
@@ -43,7 +43,7 @@ void Text::set_owner_input_element(Badge<HTML::HTMLInputElement>, HTML::HTMLInpu
 
 // https://dom.spec.whatwg.org/#dom-text-splittext
 // https://dom.spec.whatwg.org/#concept-text-split
-ExceptionOr<JS::NonnullGCPtr<Text>> Text::split_text(size_t offset)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Text>> Text::split_text(size_t offset)
 {
     // 1. Let length be node’s length.
     auto length = this->length();
diff --git a/Userland/Libraries/LibWeb/DOM/Text.h b/Userland/Libraries/LibWeb/DOM/Text.h
index f308462dab..7980275c72 100644
--- a/Userland/Libraries/LibWeb/DOM/Text.h
+++ b/Userland/Libraries/LibWeb/DOM/Text.h
@@ -29,7 +29,7 @@ public:
     void set_owner_input_element(Badge<HTML::HTMLInputElement>, HTML::HTMLInputElement&);
     HTML::HTMLInputElement* owner_input_element() { return m_owner_input_element.ptr(); }
 
-    ExceptionOr<JS::NonnullGCPtr<Text>> split_text(size_t offset);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Text>> split_text(size_t offset);
 
 protected:
     explicit Text(Document&, String const&);
diff --git a/Userland/Libraries/LibWeb/DOMParsing/InnerHTML.cpp b/Userland/Libraries/LibWeb/DOMParsing/InnerHTML.cpp
index 245dbeb049..bacbcf35dd 100644
--- a/Userland/Libraries/LibWeb/DOMParsing/InnerHTML.cpp
+++ b/Userland/Libraries/LibWeb/DOMParsing/InnerHTML.cpp
@@ -5,14 +5,14 @@
  */
 
 #include <LibWeb/DOM/DocumentFragment.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOMParsing/InnerHTML.h>
 #include <LibWeb/HTML/Parser/HTMLParser.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOMParsing {
 
 // https://w3c.github.io/DOM-Parsing/#dfn-fragment-parsing-algorithm
-DOM::ExceptionOr<JS::NonnullGCPtr<DOM::DocumentFragment>> parse_fragment(String const& markup, DOM::Element& context_element)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<DOM::DocumentFragment>> parse_fragment(String const& markup, DOM::Element& context_element)
 {
     // FIXME: Handle XML documents.
 
@@ -30,7 +30,7 @@ DOM::ExceptionOr<JS::NonnullGCPtr<DOM::DocumentFragment>> parse_fragment(String
 }
 
 // https://w3c.github.io/DOM-Parsing/#dom-innerhtml-innerhtml
-DOM::ExceptionOr<void> inner_html_setter(JS::NonnullGCPtr<DOM::Node> context_object, String const& value)
+WebIDL::ExceptionOr<void> inner_html_setter(JS::NonnullGCPtr<DOM::Node> context_object, String const& value)
 {
     // 1. Let context element be the context object's host if the context object is a ShadowRoot object, or the context object otherwise.
     //    (This is handled in Element and ShadowRoot)
diff --git a/Userland/Libraries/LibWeb/DOMParsing/InnerHTML.h b/Userland/Libraries/LibWeb/DOMParsing/InnerHTML.h
index 9619254e14..c9d6512d98 100644
--- a/Userland/Libraries/LibWeb/DOMParsing/InnerHTML.h
+++ b/Userland/Libraries/LibWeb/DOMParsing/InnerHTML.h
@@ -7,15 +7,15 @@
 #pragma once
 
 #include <LibWeb/DOM/Element.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/ShadowRoot.h>
 #include <LibWeb/HTML/HTMLTemplateElement.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOMParsing {
 
 // https://w3c.github.io/DOM-Parsing/#dom-innerhtml-innerhtml
-DOM::ExceptionOr<void> inner_html_setter(JS::NonnullGCPtr<DOM::Node> context_object, String const& value);
+WebIDL::ExceptionOr<void> inner_html_setter(JS::NonnullGCPtr<DOM::Node> context_object, String const& value);
 
-DOM::ExceptionOr<JS::NonnullGCPtr<DOM::DocumentFragment>> parse_fragment(String const& markup, DOM::Element& context_element);
+WebIDL::ExceptionOr<JS::NonnullGCPtr<DOM::DocumentFragment>> parse_fragment(String const& markup, DOM::Element& context_element);
 
 }
diff --git a/Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.cpp b/Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.cpp
index f2f8711472..52055c260f 100644
--- a/Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.cpp
+++ b/Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.cpp
@@ -10,13 +10,13 @@
 #include <LibWeb/DOM/DocumentFragment.h>
 #include <LibWeb/DOM/DocumentType.h>
 #include <LibWeb/DOM/Element.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/Node.h>
 #include <LibWeb/DOM/ProcessingInstruction.h>
 #include <LibWeb/DOM/Text.h>
 #include <LibWeb/DOMParsing/XMLSerializer.h>
 #include <LibWeb/HTML/HTMLTemplateElement.h>
 #include <LibWeb/Namespace.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOMParsing {
 
@@ -34,7 +34,7 @@ XMLSerializer::XMLSerializer(HTML::Window& window)
 XMLSerializer::~XMLSerializer() = default;
 
 // https://w3c.github.io/DOM-Parsing/#dom-xmlserializer-serializetostring
-DOM::ExceptionOr<String> XMLSerializer::serialize_to_string(JS::NonnullGCPtr<DOM::Node> root)
+WebIDL::ExceptionOr<String> XMLSerializer::serialize_to_string(JS::NonnullGCPtr<DOM::Node> root)
 {
     // The serializeToString(root) method must produce an XML serialization of root passing a value of false for the require well-formed parameter, and return the result.
     return serialize_node_to_xml_string(root, RequireWellFormed::No);
@@ -113,10 +113,10 @@ static bool prefix_is_in_prefix_map(String const& prefix, HashMap<FlyString, Vec
     return candidates_list_iterator->value.contains_slow(prefix);
 }
 
-DOM::ExceptionOr<String> serialize_node_to_xml_string_impl(JS::NonnullGCPtr<DOM::Node> root, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed);
+WebIDL::ExceptionOr<String> serialize_node_to_xml_string_impl(JS::NonnullGCPtr<DOM::Node> root, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed);
 
 // https://w3c.github.io/DOM-Parsing/#dfn-xml-serialization
-DOM::ExceptionOr<String> serialize_node_to_xml_string(JS::NonnullGCPtr<DOM::Node> root, RequireWellFormed require_well_formed)
+WebIDL::ExceptionOr<String> serialize_node_to_xml_string(JS::NonnullGCPtr<DOM::Node> root, RequireWellFormed require_well_formed)
 {
     // 1. Let namespace be a context namespace with value null. The context namespace tracks the XML serialization algorithm's current default namespace.
     //    The context namespace is changed when either an Element Node has a default namespace declaration, or the algorithm generates a default namespace declaration
@@ -140,16 +140,16 @@ DOM::ExceptionOr<String> serialize_node_to_xml_string(JS::NonnullGCPtr<DOM::Node
     return serialize_node_to_xml_string_impl(root, namespace_, prefix_map, prefix_index, require_well_formed);
 }
 
-static DOM::ExceptionOr<String> serialize_element(DOM::Element const& element, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed);
-static DOM::ExceptionOr<String> serialize_document(DOM::Document const& document, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed);
-static DOM::ExceptionOr<String> serialize_comment(DOM::Comment const& comment, RequireWellFormed require_well_formed);
-static DOM::ExceptionOr<String> serialize_text(DOM::Text const& text, RequireWellFormed require_well_formed);
-static DOM::ExceptionOr<String> serialize_document_fragment(DOM::DocumentFragment const& document_fragment, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed);
-static DOM::ExceptionOr<String> serialize_document_type(DOM::DocumentType const& document_type, RequireWellFormed require_well_formed);
-static DOM::ExceptionOr<String> serialize_processing_instruction(DOM::ProcessingInstruction const& processing_instruction, RequireWellFormed require_well_formed);
+static WebIDL::ExceptionOr<String> serialize_element(DOM::Element const& element, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed);
+static WebIDL::ExceptionOr<String> serialize_document(DOM::Document const& document, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed);
+static WebIDL::ExceptionOr<String> serialize_comment(DOM::Comment const& comment, RequireWellFormed require_well_formed);
+static WebIDL::ExceptionOr<String> serialize_text(DOM::Text const& text, RequireWellFormed require_well_formed);
+static WebIDL::ExceptionOr<String> serialize_document_fragment(DOM::DocumentFragment const& document_fragment, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed);
+static WebIDL::ExceptionOr<String> serialize_document_type(DOM::DocumentType const& document_type, RequireWellFormed require_well_formed);
+static WebIDL::ExceptionOr<String> serialize_processing_instruction(DOM::ProcessingInstruction const& processing_instruction, RequireWellFormed require_well_formed);
 
 // https://w3c.github.io/DOM-Parsing/#dfn-xml-serialization-algorithm
-DOM::ExceptionOr<String> serialize_node_to_xml_string_impl(JS::NonnullGCPtr<DOM::Node> root, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed)
+WebIDL::ExceptionOr<String> serialize_node_to_xml_string_impl(JS::NonnullGCPtr<DOM::Node> root, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed)
 {
     // Each of the following algorithms for producing an XML serialization of a DOM node take as input a node to serialize and the following arguments:
     // - A context namespace namespace
@@ -212,7 +212,7 @@ DOM::ExceptionOr<String> serialize_node_to_xml_string_impl(JS::NonnullGCPtr<DOM:
 
     // -> Anything else
     //    Throw a TypeError. Only Nodes and Attr objects can be serialized by this algorithm.
-    return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Can only serialize Nodes or Attributes." };
+    return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Can only serialize Nodes or Attributes." };
 }
 
 // https://w3c.github.io/DOM-Parsing/#dfn-recording-the-namespace-information
@@ -273,7 +273,7 @@ static Optional<String> record_namespace_information(DOM::Element const& element
 }
 
 // https://w3c.github.io/DOM-Parsing/#dfn-serializing-an-attribute-value
-static DOM::ExceptionOr<String> serialize_an_attribute_value(String const& attribute_value, [[maybe_unused]] RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_an_attribute_value(String const& attribute_value, [[maybe_unused]] RequireWellFormed require_well_formed)
 {
     // FIXME: 1. If the require well-formed flag is set (its value is true), and attribute value contains characters that are not matched by the XML Char production,
     //           then throw an exception; the serialization of this attribute value would fail to produce a well-formed element serialization.
@@ -306,7 +306,7 @@ struct LocalNameSetEntry {
 };
 
 // https://w3c.github.io/DOM-Parsing/#dfn-xml-serialization-of-the-attributes
-static DOM::ExceptionOr<String> serialize_element_attributes(DOM::Element const& element, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, HashMap<String, String> const& local_prefixes_map, bool ignore_namespace_definition_attribute, RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_element_attributes(DOM::Element const& element, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, HashMap<String, String> const& local_prefixes_map, bool ignore_namespace_definition_attribute, RequireWellFormed require_well_formed)
 {
     auto& global_object = element.global_object();
 
@@ -459,7 +459,7 @@ static DOM::ExceptionOr<String> serialize_element_attributes(DOM::Element const&
 }
 
 // https://w3c.github.io/DOM-Parsing/#xml-serializing-an-element-node
-static DOM::ExceptionOr<String> serialize_element(DOM::Element const& element, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_element(DOM::Element const& element, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed)
 {
     auto& global_object = element.global_object();
 
@@ -701,7 +701,7 @@ static DOM::ExceptionOr<String> serialize_element(DOM::Element const& element, O
 }
 
 // https://w3c.github.io/DOM-Parsing/#xml-serializing-a-document-node
-static DOM::ExceptionOr<String> serialize_document(DOM::Document const& document, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_document(DOM::Document const& document, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed)
 {
     // If the require well-formed flag is set (its value is true), and this node has no documentElement (the documentElement attribute's value is null),
     // then throw an exception; the serialization of this node would not be a well-formed document.
@@ -721,7 +721,7 @@ static DOM::ExceptionOr<String> serialize_document(DOM::Document const& document
 }
 
 // https://w3c.github.io/DOM-Parsing/#xml-serializing-a-comment-node
-static DOM::ExceptionOr<String> serialize_comment(DOM::Comment const& comment, RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_comment(DOM::Comment const& comment, RequireWellFormed require_well_formed)
 {
     // If the require well-formed flag is set (its value is true), and node's data contains characters that are not matched by the XML Char production
     // or contains "--" (two adjacent U+002D HYPHEN-MINUS characters) or that ends with a "-" (U+002D HYPHEN-MINUS) character, then throw an exception;
@@ -741,7 +741,7 @@ static DOM::ExceptionOr<String> serialize_comment(DOM::Comment const& comment, R
 }
 
 // https://w3c.github.io/DOM-Parsing/#xml-serializing-a-text-node
-static DOM::ExceptionOr<String> serialize_text(DOM::Text const& text, [[maybe_unused]] RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_text(DOM::Text const& text, [[maybe_unused]] RequireWellFormed require_well_formed)
 {
     // FIXME: 1. If the require well-formed flag is set (its value is true), and node's data contains characters that are not matched by the XML Char production,
     //           then throw an exception; the serialization of this node's data would not be well-formed.
@@ -763,7 +763,7 @@ static DOM::ExceptionOr<String> serialize_text(DOM::Text const& text, [[maybe_un
 }
 
 // https://w3c.github.io/DOM-Parsing/#xml-serializing-a-documentfragment-node
-static DOM::ExceptionOr<String> serialize_document_fragment(DOM::DocumentFragment const& document_fragment, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_document_fragment(DOM::DocumentFragment const& document_fragment, Optional<FlyString>& namespace_, HashMap<FlyString, Vector<String>>& namespace_prefix_map, u64& prefix_index, RequireWellFormed require_well_formed)
 {
     // 1. Let markup the empty string.
     StringBuilder markup;
@@ -778,7 +778,7 @@ static DOM::ExceptionOr<String> serialize_document_fragment(DOM::DocumentFragmen
 }
 
 // https://w3c.github.io/DOM-Parsing/#xml-serializing-a-documenttype-node
-static DOM::ExceptionOr<String> serialize_document_type(DOM::DocumentType const& document_type, RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_document_type(DOM::DocumentType const& document_type, RequireWellFormed require_well_formed)
 {
     if (require_well_formed == RequireWellFormed::Yes) {
         // FIXME: 1. If the require well-formed flag is true and the node's publicId attribute contains characters that are not matched by the XML PubidChar production,
@@ -844,7 +844,7 @@ static DOM::ExceptionOr<String> serialize_document_type(DOM::DocumentType const&
 }
 
 // https://w3c.github.io/DOM-Parsing/#dfn-xml-serializing-a-processinginstruction-node
-static DOM::ExceptionOr<String> serialize_processing_instruction(DOM::ProcessingInstruction const& processing_instruction, RequireWellFormed require_well_formed)
+static WebIDL::ExceptionOr<String> serialize_processing_instruction(DOM::ProcessingInstruction const& processing_instruction, RequireWellFormed require_well_formed)
 {
     if (require_well_formed == RequireWellFormed::Yes) {
         // 1. If the require well-formed flag is set (its value is true), and node's target contains a ":" (U+003A COLON) character
diff --git a/Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.h b/Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.h
index 3178e3569b..be14dbe6c3 100644
--- a/Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.h
+++ b/Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.h
@@ -18,7 +18,7 @@ public:
 
     virtual ~XMLSerializer() override;
 
-    DOM::ExceptionOr<String> serialize_to_string(JS::NonnullGCPtr<DOM::Node> root);
+    WebIDL::ExceptionOr<String> serialize_to_string(JS::NonnullGCPtr<DOM::Node> root);
 
 private:
     explicit XMLSerializer(HTML::Window&);
@@ -29,6 +29,6 @@ enum class RequireWellFormed {
     Yes,
 };
 
-DOM::ExceptionOr<String> serialize_node_to_xml_string(JS::NonnullGCPtr<DOM::Node> root, RequireWellFormed require_well_formed);
+WebIDL::ExceptionOr<String> serialize_node_to_xml_string(JS::NonnullGCPtr<DOM::Node> root, RequireWellFormed require_well_formed);
 
 }
diff --git a/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp b/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp
index 7556094ead..99e9e896d2 100644
--- a/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp
+++ b/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp
@@ -12,11 +12,11 @@
 
 namespace Web::Encoding {
 
-DOM::ExceptionOr<JS::NonnullGCPtr<TextDecoder>> TextDecoder::create_with_global_object(HTML::Window& window, FlyString encoding)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<TextDecoder>> TextDecoder::create_with_global_object(HTML::Window& window, FlyString encoding)
 {
     auto decoder = TextCodec::decoder_for(encoding);
     if (!decoder)
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, String::formatted("Invalid encoding {}", encoding) };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, String::formatted("Invalid encoding {}", encoding) };
 
     return JS::NonnullGCPtr(*window.heap().allocate<TextDecoder>(window.realm(), window, *decoder, move(encoding), false, false));
 }
@@ -35,7 +35,7 @@ TextDecoder::TextDecoder(HTML::Window& window, TextCodec::Decoder& decoder, FlyS
 TextDecoder::~TextDecoder() = default;
 
 // https://encoding.spec.whatwg.org/#dom-textdecoder-decode
-DOM::ExceptionOr<String> TextDecoder::decode(JS::Handle<JS::Object> const& input) const
+WebIDL::ExceptionOr<String> TextDecoder::decode(JS::Handle<JS::Object> const& input) const
 {
     // FIXME: Implement the streaming stuff.
 
diff --git a/Userland/Libraries/LibWeb/Encoding/TextDecoder.h b/Userland/Libraries/LibWeb/Encoding/TextDecoder.h
index f5f52e508e..fe37ccec45 100644
--- a/Userland/Libraries/LibWeb/Encoding/TextDecoder.h
+++ b/Userland/Libraries/LibWeb/Encoding/TextDecoder.h
@@ -11,8 +11,8 @@
 #include <LibJS/Forward.h>
 #include <LibTextCodec/Decoder.h>
 #include <LibWeb/Bindings/PlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::Encoding {
 
@@ -21,11 +21,11 @@ class TextDecoder : public Bindings::PlatformObject {
     WEB_PLATFORM_OBJECT(TextDecoder, Bindings::PlatformObject);
 
 public:
-    static DOM::ExceptionOr<JS::NonnullGCPtr<TextDecoder>> create_with_global_object(HTML::Window&, FlyString encoding);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<TextDecoder>> create_with_global_object(HTML::Window&, FlyString encoding);
 
     virtual ~TextDecoder() override;
 
-    DOM::ExceptionOr<String> decode(JS::Handle<JS::Object> const&) const;
+    WebIDL::ExceptionOr<String> decode(JS::Handle<JS::Object> const&) const;
 
     FlyString const& encoding() const { return m_encoding; }
     bool fatal() const { return m_fatal; }
diff --git a/Userland/Libraries/LibWeb/Fetch/BodyInit.cpp b/Userland/Libraries/LibWeb/Fetch/BodyInit.cpp
index 6fb629d77a..8dae6b2a20 100644
--- a/Userland/Libraries/LibWeb/Fetch/BodyInit.cpp
+++ b/Userland/Libraries/LibWeb/Fetch/BodyInit.cpp
@@ -5,17 +5,17 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Fetch/BodyInit.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Bodies.h>
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/URL/URLSearchParams.h>
 #include <LibWeb/WebIDL/AbstractOperations.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::Fetch {
 
 // https://fetch.spec.whatwg.org/#concept-bodyinit-extract
-DOM::ExceptionOr<Infrastructure::BodyWithType> extract_body(JS::Realm& realm, BodyInit const& object, bool keepalive)
+WebIDL::ExceptionOr<Infrastructure::BodyWithType> extract_body(JS::Realm& realm, BodyInit const& object, bool keepalive)
 {
     auto& window = verify_cast<HTML::Window>(realm.global_object());
 
@@ -38,7 +38,7 @@ DOM::ExceptionOr<Infrastructure::BodyWithType> extract_body(JS::Realm& realm, Bo
     // 6. Switch on object.
     // FIXME: Still need to support BufferSource and FormData
     TRY(object.visit(
-        [&](JS::Handle<FileAPI::Blob> const& blob) -> DOM::ExceptionOr<void> {
+        [&](JS::Handle<FileAPI::Blob> const& blob) -> WebIDL::ExceptionOr<void> {
             // FIXME: Set action to this step: read object.
             // Set source to object.
             source = blob;
@@ -49,19 +49,19 @@ DOM::ExceptionOr<Infrastructure::BodyWithType> extract_body(JS::Realm& realm, Bo
                 type = blob->type().to_byte_buffer();
             return {};
         },
-        [&](JS::Handle<JS::Object> const& buffer_source) -> DOM::ExceptionOr<void> {
+        [&](JS::Handle<JS::Object> const& buffer_source) -> WebIDL::ExceptionOr<void> {
             // Set source to a copy of the bytes held by object.
             source = TRY_OR_RETURN_OOM(window, WebIDL::get_buffer_source_copy(*buffer_source.cell()));
             return {};
         },
-        [&](JS::Handle<URL::URLSearchParams> const& url_search_params) -> DOM::ExceptionOr<void> {
+        [&](JS::Handle<URL::URLSearchParams> const& url_search_params) -> WebIDL::ExceptionOr<void> {
             // Set source to the result of running the application/x-www-form-urlencoded serializer with object’s list.
             source = url_search_params->to_string().to_byte_buffer();
             // Set type to `application/x-www-form-urlencoded;charset=UTF-8`.
             type = TRY_OR_RETURN_OOM(window, ByteBuffer::copy("application/x-www-form-urlencoded;charset=UTF-8"sv.bytes()));
             return {};
         },
-        [&](String const& scalar_value_string) -> DOM::ExceptionOr<void> {
+        [&](String const& scalar_value_string) -> WebIDL::ExceptionOr<void> {
             // NOTE: AK::String is always UTF-8.
             // Set source to the UTF-8 encoding of object.
             source = scalar_value_string.to_byte_buffer();
@@ -69,14 +69,14 @@ DOM::ExceptionOr<Infrastructure::BodyWithType> extract_body(JS::Realm& realm, Bo
             type = TRY_OR_RETURN_OOM(window, ByteBuffer::copy("text/plain;charset=UTF-8"sv.bytes()));
             return {};
         },
-        [&](JS::Handle<Streams::ReadableStream> const& stream) -> DOM::ExceptionOr<void> {
+        [&](JS::Handle<Streams::ReadableStream> const& stream) -> WebIDL::ExceptionOr<void> {
             // If keepalive is true, then throw a TypeError.
             if (keepalive)
-                return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Cannot extract body from stream when keepalive is set" };
+                return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Cannot extract body from stream when keepalive is set" };
 
             // If object is disturbed or locked, then throw a TypeError.
             if (stream->is_disturbed() || stream->is_locked())
-                return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Cannot extract body from disturbed or locked stream" };
+                return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Cannot extract body from disturbed or locked stream" };
 
             return {};
         }));
diff --git a/Userland/Libraries/LibWeb/Fetch/BodyInit.h b/Userland/Libraries/LibWeb/Fetch/BodyInit.h
index f60d3ade2e..3955a44839 100644
--- a/Userland/Libraries/LibWeb/Fetch/BodyInit.h
+++ b/Userland/Libraries/LibWeb/Fetch/BodyInit.h
@@ -19,6 +19,6 @@ using XMLHttpRequestBodyInit = Variant<JS::Handle<FileAPI::Blob>, JS::Handle<JS:
 // https://fetch.spec.whatwg.org/#bodyinit
 using BodyInit = Variant<JS::Handle<Streams::ReadableStream>, JS::Handle<FileAPI::Blob>, JS::Handle<JS::Object>, JS::Handle<URL::URLSearchParams>, String>;
 
-DOM::ExceptionOr<Infrastructure::BodyWithType> extract_body(JS::Realm&, BodyInit const&, bool keepalive = false);
+WebIDL::ExceptionOr<Infrastructure::BodyWithType> extract_body(JS::Realm&, BodyInit const&, bool keepalive = false);
 
 }
diff --git a/Userland/Libraries/LibWeb/Fetch/Headers.cpp b/Userland/Libraries/LibWeb/Fetch/Headers.cpp
index 4195c98aa2..c921e54992 100644
--- a/Userland/Libraries/LibWeb/Fetch/Headers.cpp
+++ b/Userland/Libraries/LibWeb/Fetch/Headers.cpp
@@ -11,7 +11,7 @@
 namespace Web::Fetch {
 
 // https://fetch.spec.whatwg.org/#dom-headers
-DOM::ExceptionOr<JS::NonnullGCPtr<Headers>> Headers::create_with_global_object(HTML::Window& window, Optional<HeadersInit> const& init)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Headers>> Headers::create_with_global_object(HTML::Window& window, Optional<HeadersInit> const& init)
 {
     // The new Headers(init) constructor steps are:
     auto* headers = window.heap().allocate<Headers>(window.realm(), window);
@@ -35,7 +35,7 @@ Headers::Headers(HTML::Window& window)
 Headers::~Headers() = default;
 
 // https://fetch.spec.whatwg.org/#dom-headers-append
-DOM::ExceptionOr<void> Headers::append(String const& name_string, String const& value_string)
+WebIDL::ExceptionOr<void> Headers::append(String const& name_string, String const& value_string)
 {
     // The append(name, value) method steps are to append (name, value) to this.
     auto header = Infrastructure::Header {
@@ -47,18 +47,18 @@ DOM::ExceptionOr<void> Headers::append(String const& name_string, String const&
 }
 
 // https://fetch.spec.whatwg.org/#dom-headers-delete
-DOM::ExceptionOr<void> Headers::delete_(String const& name_string)
+WebIDL::ExceptionOr<void> Headers::delete_(String const& name_string)
 {
     // The delete(name) method steps are:
     auto name = name_string.bytes();
 
     // 1. If name is not a header name, then throw a TypeError.
     if (!Infrastructure::is_header_name(name))
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid header name" };
 
     // 2. If this’s guard is "immutable", then throw a TypeError.
     if (m_guard == Guard::Immutable)
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Headers object is immutable" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Headers object is immutable" };
 
     // 3. Otherwise, if this’s guard is "request" and name is a forbidden header name, return.
     if (m_guard == Guard::Request && Infrastructure::is_forbidden_header_name(name))
@@ -87,14 +87,14 @@ DOM::ExceptionOr<void> Headers::delete_(String const& name_string)
 }
 
 // https://fetch.spec.whatwg.org/#dom-headers-get
-DOM::ExceptionOr<String> Headers::get(String const& name_string)
+WebIDL::ExceptionOr<String> Headers::get(String const& name_string)
 {
     // The get(name) method steps are:
     auto name = name_string.bytes();
 
     // 1. If name is not a header name, then throw a TypeError.
     if (!Infrastructure::is_header_name(name))
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid header name" };
 
     // 2. Return the result of getting name from this’s header list.
     auto byte_buffer = TRY_OR_RETURN_OOM(global_object(), m_header_list.get(name));
@@ -103,21 +103,21 @@ DOM::ExceptionOr<String> Headers::get(String const& name_string)
 }
 
 // https://fetch.spec.whatwg.org/#dom-headers-has
-DOM::ExceptionOr<bool> Headers::has(String const& name_string)
+WebIDL::ExceptionOr<bool> Headers::has(String const& name_string)
 {
     // The has(name) method steps are:
     auto name = name_string.bytes();
 
     // 1. If name is not a header name, then throw a TypeError.
     if (!Infrastructure::is_header_name(name))
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid header name" };
 
     // 2. Return true if this’s header list contains name; otherwise false.
     return m_header_list.contains(name);
 }
 
 // https://fetch.spec.whatwg.org/#dom-headers-set
-DOM::ExceptionOr<void> Headers::set(String const& name_string, String const& value_string)
+WebIDL::ExceptionOr<void> Headers::set(String const& name_string, String const& value_string)
 {
     // The set(name, value) method steps are:
     auto name = name_string.bytes();
@@ -133,13 +133,13 @@ DOM::ExceptionOr<void> Headers::set(String const& name_string, String const& val
 
     // 2. If name is not a header name or value is not a header value, then throw a TypeError.
     if (!Infrastructure::is_header_name(name))
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid header name" };
     if (!Infrastructure::is_header_value(value))
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header value" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid header value" };
 
     // 3. If this’s guard is "immutable", then throw a TypeError.
     if (m_guard == Guard::Immutable)
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Headers object is immutable" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Headers object is immutable" };
 
     // 4. Otherwise, if this’s guard is "request" and name is a forbidden header name, return.
     if (m_guard == Guard::Request && Infrastructure::is_forbidden_header_name(name))
@@ -201,7 +201,7 @@ JS::ThrowCompletionOr<void> Headers::for_each(ForEachCallback callback)
 }
 
 // https://fetch.spec.whatwg.org/#concept-headers-append
-DOM::ExceptionOr<void> Headers::append(Infrastructure::Header header)
+WebIDL::ExceptionOr<void> Headers::append(Infrastructure::Header header)
 {
     // To append a header (name, value) to a Headers object headers, run these steps:
     auto& [name, value] = header;
@@ -211,13 +211,13 @@ DOM::ExceptionOr<void> Headers::append(Infrastructure::Header header)
 
     // 2. If name is not a header name or value is not a header value, then throw a TypeError.
     if (!Infrastructure::is_header_name(name))
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid header name" };
     if (!Infrastructure::is_header_value(value))
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header value" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid header value" };
 
     // 3. If headers’s guard is "immutable", then throw a TypeError.
     if (m_guard == Guard::Immutable)
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Headers object is immutable" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Headers object is immutable" };
 
     // 4. Otherwise, if headers’s guard is "request" and name is a forbidden header name, return.
     if (m_guard == Guard::Request && Infrastructure::is_forbidden_header_name(name))
@@ -264,16 +264,16 @@ DOM::ExceptionOr<void> Headers::append(Infrastructure::Header header)
 }
 
 // https://fetch.spec.whatwg.org/#concept-headers-fill
-DOM::ExceptionOr<void> Headers::fill(HeadersInit const& object)
+WebIDL::ExceptionOr<void> Headers::fill(HeadersInit const& object)
 {
     // To fill a Headers object headers with a given object object, run these steps:
     return object.visit(
         // 1. If object is a sequence, then for each header in object:
-        [this](Vector<Vector<String>> const& object) -> DOM::ExceptionOr<void> {
+        [this](Vector<Vector<String>> const& object) -> WebIDL::ExceptionOr<void> {
             for (auto const& entry : object) {
                 // 1. If header does not contain exactly two items, then throw a TypeError.
                 if (entry.size() != 2)
-                    return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Array must contain header key/value pair" };
+                    return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Array must contain header key/value pair" };
 
                 // 2. Append (header’s first item, header’s second item) to headers.
                 auto header = Fetch::Infrastructure::Header {
@@ -285,7 +285,7 @@ DOM::ExceptionOr<void> Headers::fill(HeadersInit const& object)
             return {};
         },
         // 2. Otherwise, object is a record, then for each key → value in object, append (key, value) to headers.
-        [this](OrderedHashMap<String, String> const& object) -> DOM::ExceptionOr<void> {
+        [this](OrderedHashMap<String, String> const& object) -> WebIDL::ExceptionOr<void> {
             for (auto const& entry : object) {
                 auto header = Fetch::Infrastructure::Header {
                     .name = TRY_OR_RETURN_OOM(global_object(), ByteBuffer::copy(entry.key.bytes())),
diff --git a/Userland/Libraries/LibWeb/Fetch/Headers.h b/Userland/Libraries/LibWeb/Fetch/Headers.h
index 84e99c61cb..e5c6cebcab 100644
--- a/Userland/Libraries/LibWeb/Fetch/Headers.h
+++ b/Userland/Libraries/LibWeb/Fetch/Headers.h
@@ -11,8 +11,8 @@
 #include <AK/Variant.h>
 #include <AK/Vector.h>
 #include <LibWeb/Bindings/PlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Headers.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::Fetch {
 
@@ -31,16 +31,16 @@ public:
         None,
     };
 
-    static DOM::ExceptionOr<JS::NonnullGCPtr<Headers>> create_with_global_object(HTML::Window& window, Optional<HeadersInit> const& init);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<Headers>> create_with_global_object(HTML::Window& window, Optional<HeadersInit> const& init);
 
     virtual ~Headers() override;
 
-    DOM::ExceptionOr<void> append(Infrastructure::Header);
-    DOM::ExceptionOr<void> append(String const& name, String const& value);
-    DOM::ExceptionOr<void> delete_(String const& name);
-    DOM::ExceptionOr<String> get(String const& name);
-    DOM::ExceptionOr<bool> has(String const& name);
-    DOM::ExceptionOr<void> set(String const& name, String const& value);
+    WebIDL::ExceptionOr<void> append(Infrastructure::Header);
+    WebIDL::ExceptionOr<void> append(String const& name, String const& value);
+    WebIDL::ExceptionOr<void> delete_(String const& name);
+    WebIDL::ExceptionOr<String> get(String const& name);
+    WebIDL::ExceptionOr<bool> has(String const& name);
+    WebIDL::ExceptionOr<void> set(String const& name, String const& value);
 
     using ForEachCallback = Function<JS::ThrowCompletionOr<void>(String const&, String const&)>;
     JS::ThrowCompletionOr<void> for_each(ForEachCallback);
@@ -50,7 +50,7 @@ private:
 
     explicit Headers(HTML::Window&);
 
-    DOM::ExceptionOr<void> fill(HeadersInit const&);
+    WebIDL::ExceptionOr<void> fill(HeadersInit const&);
     void remove_privileged_no_cors_headers();
 
     // https://fetch.spec.whatwg.org/#concept-headers-header-list
diff --git a/Userland/Libraries/LibWeb/FileAPI/Blob.cpp b/Userland/Libraries/LibWeb/FileAPI/Blob.cpp
index 510be487f4..a1d721f7fc 100644
--- a/Userland/Libraries/LibWeb/FileAPI/Blob.cpp
+++ b/Userland/Libraries/LibWeb/FileAPI/Blob.cpp
@@ -135,7 +135,7 @@ Blob::Blob(HTML::Window& window, ByteBuffer byte_buffer)
 Blob::~Blob() = default;
 
 // https://w3c.github.io/FileAPI/#ref-for-dom-blob-blob
-DOM::ExceptionOr<JS::NonnullGCPtr<Blob>> Blob::create(HTML::Window& window, Optional<Vector<BlobPart>> const& blob_parts, Optional<BlobPropertyBag> const& options)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Blob>> Blob::create(HTML::Window& window, Optional<Vector<BlobPart>> const& blob_parts, Optional<BlobPropertyBag> const& options)
 {
     // 1. If invoked with zero parameters, return a new Blob object consisting of 0 bytes, with size set to 0, and with type set to the empty string.
     if (!blob_parts.has_value() && !options.has_value())
@@ -167,13 +167,13 @@ DOM::ExceptionOr<JS::NonnullGCPtr<Blob>> Blob::create(HTML::Window& window, Opti
     return JS::NonnullGCPtr(*window.heap().allocate<Blob>(window.realm(), window, move(byte_buffer), move(type)));
 }
 
-DOM::ExceptionOr<JS::NonnullGCPtr<Blob>> Blob::create_with_global_object(HTML::Window& window, Optional<Vector<BlobPart>> const& blob_parts, Optional<BlobPropertyBag> const& options)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Blob>> Blob::create_with_global_object(HTML::Window& window, Optional<Vector<BlobPart>> const& blob_parts, Optional<BlobPropertyBag> const& options)
 {
     return Blob::create(window, blob_parts, options);
 }
 
 // https://w3c.github.io/FileAPI/#dfn-slice
-DOM::ExceptionOr<JS::NonnullGCPtr<Blob>> Blob::slice(Optional<i64> start, Optional<i64> end, Optional<String> const& content_type)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Blob>> Blob::slice(Optional<i64> start, Optional<i64> end, Optional<String> const& content_type)
 {
     // 1. The optional start parameter is a value for the start point of a slice() call, and must be treated as a byte-order position, with the zeroth position representing the first byte.
     //    User agents must process slice() with start normalized according to the following:
diff --git a/Userland/Libraries/LibWeb/FileAPI/Blob.h b/Userland/Libraries/LibWeb/FileAPI/Blob.h
index d85bc94cb2..26babfbd40 100644
--- a/Userland/Libraries/LibWeb/FileAPI/Blob.h
+++ b/Userland/Libraries/LibWeb/FileAPI/Blob.h
@@ -11,8 +11,8 @@
 #include <AK/Vector.h>
 #include <LibWeb/Bindings/BlobPrototype.h>
 #include <LibWeb/Bindings/PlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::FileAPI {
 
@@ -34,15 +34,15 @@ public:
     virtual ~Blob() override;
 
     static JS::NonnullGCPtr<Blob> create(HTML::Window&, ByteBuffer, String type);
-    static DOM::ExceptionOr<JS::NonnullGCPtr<Blob>> create(HTML::Window&, Optional<Vector<BlobPart>> const& blob_parts = {}, Optional<BlobPropertyBag> const& options = {});
-    static DOM::ExceptionOr<JS::NonnullGCPtr<Blob>> create_with_global_object(HTML::Window&, Optional<Vector<BlobPart>> const& blob_parts = {}, Optional<BlobPropertyBag> const& options = {});
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<Blob>> create(HTML::Window&, Optional<Vector<BlobPart>> const& blob_parts = {}, Optional<BlobPropertyBag> const& options = {});
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<Blob>> create_with_global_object(HTML::Window&, Optional<Vector<BlobPart>> const& blob_parts = {}, Optional<BlobPropertyBag> const& options = {});
 
     // https://w3c.github.io/FileAPI/#dfn-size
     u64 size() const { return m_byte_buffer.size(); }
     // https://w3c.github.io/FileAPI/#dfn-type
     String const& type() const { return m_type; }
 
-    DOM::ExceptionOr<JS::NonnullGCPtr<Blob>> slice(Optional<i64> start = {}, Optional<i64> end = {}, Optional<String> const& content_type = {});
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Blob>> slice(Optional<i64> start = {}, Optional<i64> end = {}, Optional<String> const& content_type = {});
 
     JS::Promise* text();
     JS::Promise* array_buffer();
diff --git a/Userland/Libraries/LibWeb/FileAPI/File.cpp b/Userland/Libraries/LibWeb/FileAPI/File.cpp
index f431134bca..7f8e0f4e45 100644
--- a/Userland/Libraries/LibWeb/FileAPI/File.cpp
+++ b/Userland/Libraries/LibWeb/FileAPI/File.cpp
@@ -20,7 +20,7 @@ File::File(HTML::Window& window, ByteBuffer byte_buffer, String file_name, Strin
 File::~File() = default;
 
 // https://w3c.github.io/FileAPI/#ref-for-dom-file-file
-DOM::ExceptionOr<JS::NonnullGCPtr<File>> File::create(HTML::Window& window, Vector<BlobPart> const& file_bits, String const& file_name, Optional<FilePropertyBag> const& options)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<File>> File::create(HTML::Window& window, Vector<BlobPart> const& file_bits, String const& file_name, Optional<FilePropertyBag> const& options)
 {
     // 1. Let bytes be the result of processing blob parts given fileBits and options.
     auto bytes = TRY_OR_RETURN_OOM(window, process_blob_parts(file_bits, static_cast<Optional<BlobPropertyBag> const&>(*options)));
@@ -60,7 +60,7 @@ DOM::ExceptionOr<JS::NonnullGCPtr<File>> File::create(HTML::Window& window, Vect
     return JS::NonnullGCPtr(*window.heap().allocate<File>(window.realm(), window, move(bytes), move(name), move(type), last_modified));
 }
 
-DOM::ExceptionOr<JS::NonnullGCPtr<File>> File::create_with_global_object(HTML::Window& window, Vector<BlobPart> const& file_bits, String const& file_name, Optional<FilePropertyBag> const& options)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<File>> File::create_with_global_object(HTML::Window& window, Vector<BlobPart> const& file_bits, String const& file_name, Optional<FilePropertyBag> const& options)
 {
     return create(window, file_bits, file_name, options);
 }
diff --git a/Userland/Libraries/LibWeb/FileAPI/File.h b/Userland/Libraries/LibWeb/FileAPI/File.h
index 82f2817722..0ad1238d1c 100644
--- a/Userland/Libraries/LibWeb/FileAPI/File.h
+++ b/Userland/Libraries/LibWeb/FileAPI/File.h
@@ -19,8 +19,8 @@ class File : public Blob {
     WEB_PLATFORM_OBJECT(File, Blob);
 
 public:
-    static DOM::ExceptionOr<JS::NonnullGCPtr<File>> create(HTML::Window&, Vector<BlobPart> const& file_bits, String const& file_name, Optional<FilePropertyBag> const& options = {});
-    static DOM::ExceptionOr<JS::NonnullGCPtr<File>> create_with_global_object(HTML::Window&, Vector<BlobPart> const& file_bits, String const& file_name, Optional<FilePropertyBag> const& options = {});
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<File>> create(HTML::Window&, Vector<BlobPart> const& file_bits, String const& file_name, Optional<FilePropertyBag> const& options = {});
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<File>> create_with_global_object(HTML::Window&, Vector<BlobPart> const& file_bits, String const& file_name, Optional<FilePropertyBag> const& options = {});
 
     virtual ~File() override;
 
diff --git a/Userland/Libraries/LibWeb/Forward.h b/Userland/Libraries/LibWeb/Forward.h
index d9f9510f71..465a9343bb 100644
--- a/Userland/Libraries/LibWeb/Forward.h
+++ b/Userland/Libraries/LibWeb/Forward.h
@@ -170,9 +170,6 @@ class TreeWalker;
 enum class QuirksMode;
 struct EventListenerOptions;
 struct AddEventListenerOptions;
-
-template<typename ValueType>
-class ExceptionOr;
 }
 
 namespace Web::DOMParsing {
@@ -397,6 +394,9 @@ class SVGSVGElement;
 
 namespace Web::WebIDL {
 class CallbackType;
+
+template<typename ValueType>
+class ExceptionOr;
 }
 
 namespace Web::WebSockets {
diff --git a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
index 5e2e9da965..416ca237be 100644
--- a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
+++ b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
@@ -859,7 +859,7 @@ void BrowsingContext::remove()
 }
 
 // https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigate
-DOM::ExceptionOr<void> BrowsingContext::navigate(
+WebIDL::ExceptionOr<void> BrowsingContext::navigate(
     Fetch::Infrastructure::Request resource,
     BrowsingContext& source_browsing_context,
     bool exceptions_enabled,
@@ -983,7 +983,7 @@ DOM::ExceptionOr<void> BrowsingContext::navigate(
 }
 
 // https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigate-fragid
-DOM::ExceptionOr<void> BrowsingContext::navigate_to_a_fragment(AK::URL const& url, HistoryHandlingBehavior history_handling, String navigation_id)
+WebIDL::ExceptionOr<void> BrowsingContext::navigate_to_a_fragment(AK::URL const& url, HistoryHandlingBehavior history_handling, String navigation_id)
 {
     // 1. If historyHandling is not "replace",
     if (history_handling != HistoryHandlingBehavior::Replace) {
@@ -1025,7 +1025,7 @@ DOM::ExceptionOr<void> BrowsingContext::navigate_to_a_fragment(AK::URL const& ur
 }
 
 // https://html.spec.whatwg.org/multipage/browsing-the-web.html#traverse-the-history
-DOM::ExceptionOr<void> BrowsingContext::traverse_the_history(size_t entry_index, HistoryHandlingBehavior history_handling, bool explicit_history_navigation)
+WebIDL::ExceptionOr<void> BrowsingContext::traverse_the_history(size_t entry_index, HistoryHandlingBehavior history_handling, bool explicit_history_navigation)
 {
     auto* entry = &m_session_history[entry_index];
 
diff --git a/Userland/Libraries/LibWeb/HTML/BrowsingContext.h b/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
index 29a8f1edb6..23fef535bd 100644
--- a/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
+++ b/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
@@ -140,7 +140,7 @@ public:
     bool is_allowed_to_navigate(BrowsingContext const&) const;
 
     // https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigate
-    DOM::ExceptionOr<void> navigate(
+    WebIDL::ExceptionOr<void> navigate(
         Fetch::Infrastructure::Request resource,
         BrowsingContext& source_browsing_context,
         bool exceptions_enabled = false,
@@ -151,13 +151,13 @@ public:
         Function<void(NonnullOwnPtr<Fetch::Infrastructure::Response>)> process_response_end_of_body = {});
 
     // https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigate-fragid
-    DOM::ExceptionOr<void> navigate_to_a_fragment(AK::URL const&, HistoryHandlingBehavior, String navigation_id);
+    WebIDL::ExceptionOr<void> navigate_to_a_fragment(AK::URL const&, HistoryHandlingBehavior, String navigation_id);
 
     // https://html.spec.whatwg.org/multipage/origin.html#one-permitted-sandboxed-navigator
     BrowsingContext const* the_one_permitted_sandboxed_navigator() const;
 
     // https://html.spec.whatwg.org/multipage/browsing-the-web.html#traverse-the-history
-    DOM::ExceptionOr<void> traverse_the_history(size_t entry_index, HistoryHandlingBehavior = HistoryHandlingBehavior::Default, bool explicit_history_navigation = false);
+    WebIDL::ExceptionOr<void> traverse_the_history(size_t entry_index, HistoryHandlingBehavior = HistoryHandlingBehavior::Default, bool explicit_history_navigation = false);
 
     Vector<JS::Handle<DOM::Document>> document_family() const;
     bool document_family_contains(DOM::Document const&) const;
diff --git a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasDrawImage.cpp b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasDrawImage.cpp
index 7e4620aa22..d824ff34e3 100644
--- a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasDrawImage.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasDrawImage.cpp
@@ -21,7 +21,7 @@ static void default_source_size(CanvasImageSource const& image, float& source_wi
     });
 }
 
-DOM::ExceptionOr<void> CanvasDrawImage::draw_image(Web::HTML::CanvasImageSource const& image, float destination_x, float destination_y)
+WebIDL::ExceptionOr<void> CanvasDrawImage::draw_image(Web::HTML::CanvasImageSource const& image, float destination_x, float destination_y)
 {
     // If not specified, the dw and dh arguments must default to the values of sw and sh, interpreted such that one CSS pixel in the image is treated as one unit in the output bitmap's coordinate space.
     // If the sx, sy, sw, and sh arguments are omitted, then they must default to 0, 0, the image's intrinsic width in image pixels, and the image's intrinsic height in image pixels, respectively.
@@ -33,7 +33,7 @@ DOM::ExceptionOr<void> CanvasDrawImage::draw_image(Web::HTML::CanvasImageSource
     return draw_image_internal(image, 0, 0, source_width, source_height, destination_x, destination_y, source_width, source_height);
 }
 
-DOM::ExceptionOr<void> CanvasDrawImage::draw_image(Web::HTML::CanvasImageSource const& image, float destination_x, float destination_y, float destination_width, float destination_height)
+WebIDL::ExceptionOr<void> CanvasDrawImage::draw_image(Web::HTML::CanvasImageSource const& image, float destination_x, float destination_y, float destination_width, float destination_height)
 {
     // If the sx, sy, sw, and sh arguments are omitted, then they must default to 0, 0, the image's intrinsic width in image pixels, and the image's intrinsic height in image pixels, respectively.
     // If the image has no intrinsic dimensions, then the concrete object size must be used instead, as determined using the CSS "Concrete Object Size Resolution" algorithm, with the specified size having
@@ -44,7 +44,7 @@ DOM::ExceptionOr<void> CanvasDrawImage::draw_image(Web::HTML::CanvasImageSource
     return draw_image_internal(image, 0, 0, source_width, source_height, destination_x, destination_y, destination_width, destination_height);
 }
 
-DOM::ExceptionOr<void> CanvasDrawImage::draw_image(Web::HTML::CanvasImageSource const& image, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height)
+WebIDL::ExceptionOr<void> CanvasDrawImage::draw_image(Web::HTML::CanvasImageSource const& image, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height)
 {
     return draw_image_internal(image, source_x, source_y, source_width, source_height, destination_x, destination_y, destination_width, destination_height);
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasDrawImage.h b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasDrawImage.h
index 3a6ab3cebc..e7d324b8d8 100644
--- a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasDrawImage.h
+++ b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasDrawImage.h
@@ -7,9 +7,9 @@
 #pragma once
 
 #include <AK/String.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/HTML/HTMLCanvasElement.h>
 #include <LibWeb/HTML/HTMLImageElement.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -22,11 +22,11 @@ class CanvasDrawImage {
 public:
     virtual ~CanvasDrawImage() = default;
 
-    DOM::ExceptionOr<void> draw_image(CanvasImageSource const&, float destination_x, float destination_y);
-    DOM::ExceptionOr<void> draw_image(CanvasImageSource const&, float destination_x, float destination_y, float destination_width, float destination_height);
-    DOM::ExceptionOr<void> draw_image(CanvasImageSource const&, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height);
+    WebIDL::ExceptionOr<void> draw_image(CanvasImageSource const&, float destination_x, float destination_y);
+    WebIDL::ExceptionOr<void> draw_image(CanvasImageSource const&, float destination_x, float destination_y, float destination_width, float destination_height);
+    WebIDL::ExceptionOr<void> draw_image(CanvasImageSource const&, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height);
 
-    virtual DOM::ExceptionOr<void> draw_image_internal(CanvasImageSource const&, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height) = 0;
+    virtual WebIDL::ExceptionOr<void> draw_image_internal(CanvasImageSource const&, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height) = 0;
 
 protected:
     CanvasDrawImage() = default;
diff --git a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasImageData.h b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasImageData.h
index ba5f69ed5f..b918917363 100644
--- a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasImageData.h
+++ b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasImageData.h
@@ -16,7 +16,7 @@ public:
     virtual ~CanvasImageData() = default;
 
     virtual JS::GCPtr<ImageData> create_image_data(int width, int height) const = 0;
-    virtual DOM::ExceptionOr<JS::GCPtr<ImageData>> get_image_data(int x, int y, int width, int height) const = 0;
+    virtual WebIDL::ExceptionOr<JS::GCPtr<ImageData>> get_image_data(int x, int y, int width, int height) const = 0;
     virtual void put_image_data(ImageData const&, float x, float y) = 0;
 
 protected:
diff --git a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasPath.cpp b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasPath.cpp
index 2091832fa7..d2460f7fad 100644
--- a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasPath.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasPath.cpp
@@ -36,14 +36,14 @@ void CanvasPath::bezier_curve_to(double cp1x, double cp1y, double cp2x, double c
     m_path.cubic_bezier_curve_to(Gfx::FloatPoint(cp1x, cp1y), Gfx::FloatPoint(cp2x, cp2y), Gfx::FloatPoint(x, y));
 }
 
-DOM::ExceptionOr<void> CanvasPath::arc(float x, float y, float radius, float start_angle, float end_angle, bool counter_clockwise)
+WebIDL::ExceptionOr<void> CanvasPath::arc(float x, float y, float radius, float start_angle, float end_angle, bool counter_clockwise)
 {
     if (radius < 0)
         return DOM::IndexSizeError::create(m_self.global_object(), String::formatted("The radius provided ({}) is negative.", radius));
     return ellipse(x, y, radius, radius, 0, start_angle, end_angle, counter_clockwise);
 }
 
-DOM::ExceptionOr<void> CanvasPath::ellipse(float x, float y, float radius_x, float radius_y, float rotation, float start_angle, float end_angle, bool counter_clockwise)
+WebIDL::ExceptionOr<void> CanvasPath::ellipse(float x, float y, float radius_x, float radius_y, float rotation, float start_angle, float end_angle, bool counter_clockwise)
 {
     if (radius_x < 0)
         return DOM::IndexSizeError::create(m_self.global_object(), String::formatted("The major-axis radius provided ({}) is negative.", radius_x));
diff --git a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasPath.h b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasPath.h
index 4d9a0ecd2f..2f7130ad00 100644
--- a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasPath.h
+++ b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasPath.h
@@ -7,7 +7,7 @@
 #pragma once
 
 #include <LibGfx/Path.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -23,8 +23,8 @@ public:
     void quadratic_curve_to(float cx, float cy, float x, float y);
     void bezier_curve_to(double cp1x, double cp1y, double cp2x, double cp2y, double x, double y);
     void rect(float x, float y, float width, float height);
-    DOM::ExceptionOr<void> arc(float x, float y, float radius, float start_angle, float end_angle, bool counter_clockwise);
-    DOM::ExceptionOr<void> ellipse(float x, float y, float radius_x, float radius_y, float rotation, float start_angle, float end_angle, bool counter_clockwise);
+    WebIDL::ExceptionOr<void> arc(float x, float y, float radius, float start_angle, float end_angle, bool counter_clockwise);
+    WebIDL::ExceptionOr<void> ellipse(float x, float y, float radius_x, float radius_y, float rotation, float start_angle, float end_angle, bool counter_clockwise);
 
     Gfx::Path& path() { return m_path; }
     Gfx::Path const& path() const { return m_path; }
diff --git a/Userland/Libraries/LibWeb/HTML/CanvasGradient.cpp b/Userland/Libraries/LibWeb/HTML/CanvasGradient.cpp
index 213d301e81..e0e0b398c4 100644
--- a/Userland/Libraries/LibWeb/HTML/CanvasGradient.cpp
+++ b/Userland/Libraries/LibWeb/HTML/CanvasGradient.cpp
@@ -5,9 +5,9 @@
  */
 
 #include <AK/QuickSort.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/HTML/CanvasGradient.h>
 #include <LibWeb/HTML/Window.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -49,7 +49,7 @@ CanvasGradient::CanvasGradient(HTML::Window& window, Type type)
 CanvasGradient::~CanvasGradient() = default;
 
 // https://html.spec.whatwg.org/multipage/canvas.html#dom-canvasgradient-addcolorstop
-DOM::ExceptionOr<void> CanvasGradient::add_color_stop(double offset, String const& color)
+WebIDL::ExceptionOr<void> CanvasGradient::add_color_stop(double offset, String const& color)
 {
     // 1. If the offset is less than 0 or greater than 1, then throw an "IndexSizeError" DOMException.
     if (offset < 0 || offset > 1)
diff --git a/Userland/Libraries/LibWeb/HTML/CanvasGradient.h b/Userland/Libraries/LibWeb/HTML/CanvasGradient.h
index 56de9c855d..422222c1e3 100644
--- a/Userland/Libraries/LibWeb/HTML/CanvasGradient.h
+++ b/Userland/Libraries/LibWeb/HTML/CanvasGradient.h
@@ -25,7 +25,7 @@ public:
     static JS::NonnullGCPtr<CanvasGradient> create_linear(HTML::Window&, double x0, double y0, double x1, double y1);
     static JS::NonnullGCPtr<CanvasGradient> create_conic(HTML::Window&, double start_angle, double x, double y);
 
-    DOM::ExceptionOr<void> add_color_stop(double offset, String const& color);
+    WebIDL::ExceptionOr<void> add_color_stop(double offset, String const& color);
 
     ~CanvasGradient();
 
diff --git a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp
index 29e916fc27..2b086edf05 100644
--- a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp
+++ b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp
@@ -10,7 +10,6 @@
 #include <LibGfx/Painter.h>
 #include <LibGfx/Quad.h>
 #include <LibGfx/Rect.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/HTML/CanvasRenderingContext2D.h>
 #include <LibWeb/HTML/HTMLCanvasElement.h>
 #include <LibWeb/HTML/HTMLImageElement.h>
@@ -20,6 +19,7 @@
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/Layout/TextNode.h>
 #include <LibWeb/Platform/FontPlugin.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -107,7 +107,7 @@ void CanvasRenderingContext2D::stroke_rect(float x, float y, float width, float
 }
 
 // 4.12.5.1.14 Drawing images, https://html.spec.whatwg.org/multipage/canvas.html#drawing-images
-DOM::ExceptionOr<void> CanvasRenderingContext2D::draw_image_internal(CanvasImageSource const& image, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height)
+WebIDL::ExceptionOr<void> CanvasRenderingContext2D::draw_image_internal(CanvasImageSource const& image, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height)
 {
     // 1. If any of the arguments are infinite or NaN, then return.
     if (!isfinite(source_x) || !isfinite(source_y) || !isfinite(source_width) || !isfinite(source_height) || !isfinite(destination_x) || !isfinite(destination_y) || !isfinite(destination_width) || !isfinite(destination_height))
@@ -271,7 +271,7 @@ JS::GCPtr<ImageData> CanvasRenderingContext2D::create_image_data(int width, int
 }
 
 // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-getimagedata
-DOM::ExceptionOr<JS::GCPtr<ImageData>> CanvasRenderingContext2D::get_image_data(int x, int y, int width, int height) const
+WebIDL::ExceptionOr<JS::GCPtr<ImageData>> CanvasRenderingContext2D::get_image_data(int x, int y, int width, int height) const
 {
     // 1. If either the sw or sh arguments are zero, then throw an "IndexSizeError" DOMException.
     if (width == 0 || height == 0)
@@ -471,12 +471,12 @@ void CanvasRenderingContext2D::clip()
 }
 
 // https://html.spec.whatwg.org/multipage/canvas.html#check-the-usability-of-the-image-argument
-DOM::ExceptionOr<CanvasImageSourceUsability> check_usability_of_image(CanvasImageSource const& image)
+WebIDL::ExceptionOr<CanvasImageSourceUsability> check_usability_of_image(CanvasImageSource const& image)
 {
     // 1. Switch on image:
     auto usability = TRY(image.visit(
         // HTMLOrSVGImageElement
-        [](JS::Handle<HTMLImageElement> const& image_element) -> DOM::ExceptionOr<Optional<CanvasImageSourceUsability>> {
+        [](JS::Handle<HTMLImageElement> const& image_element) -> WebIDL::ExceptionOr<Optional<CanvasImageSourceUsability>> {
             // FIXME: If image's current request's state is broken, then throw an "InvalidStateError" DOMException.
 
             // If image is not fully decodable, then return bad.
@@ -494,7 +494,7 @@ DOM::ExceptionOr<CanvasImageSourceUsability> check_usability_of_image(CanvasImag
 
         // HTMLCanvasElement
         // FIXME: OffscreenCanvas
-        [](JS::Handle<HTMLCanvasElement> const& canvas_element) -> DOM::ExceptionOr<Optional<CanvasImageSourceUsability>> {
+        [](JS::Handle<HTMLCanvasElement> const& canvas_element) -> WebIDL::ExceptionOr<Optional<CanvasImageSourceUsability>> {
             // If image has either a horizontal dimension or a vertical dimension equal to zero, then throw an "InvalidStateError" DOMException.
             if (canvas_element->width() == 0 || canvas_element->height() == 0)
                 return DOM::InvalidStateError::create(canvas_element->global_object(), "Canvas width or height is zero");
diff --git a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h
index 3ffbd5481f..caaae49815 100644
--- a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h
+++ b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h
@@ -14,7 +14,6 @@
 #include <LibGfx/Painter.h>
 #include <LibGfx/Path.h>
 #include <LibWeb/Bindings/PlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/HTML/Canvas/CanvasDrawImage.h>
 #include <LibWeb/HTML/Canvas/CanvasDrawPath.h>
 #include <LibWeb/HTML/Canvas/CanvasFillStrokeStyles.h>
@@ -28,6 +27,7 @@
 #include <LibWeb/HTML/CanvasGradient.h>
 #include <LibWeb/Layout/InlineNode.h>
 #include <LibWeb/Layout/LineBox.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -58,7 +58,7 @@ public:
     virtual void stroke_rect(float x, float y, float width, float height) override;
     virtual void clear_rect(float x, float y, float width, float height) override;
 
-    virtual DOM::ExceptionOr<void> draw_image_internal(CanvasImageSource const&, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height) override;
+    virtual WebIDL::ExceptionOr<void> draw_image_internal(CanvasImageSource const&, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height) override;
 
     virtual void begin_path() override;
     virtual void stroke() override;
@@ -71,7 +71,7 @@ public:
     virtual void fill(Path2D& path, String const& fill_rule) override;
 
     virtual JS::GCPtr<ImageData> create_image_data(int width, int height) const override;
-    virtual DOM::ExceptionOr<JS::GCPtr<ImageData>> get_image_data(int x, int y, int width, int height) const override;
+    virtual WebIDL::ExceptionOr<JS::GCPtr<ImageData>> get_image_data(int x, int y, int width, int height) const override;
     virtual void put_image_data(ImageData const&, float x, float y) override;
 
     virtual void reset_to_default_state() override;
@@ -120,7 +120,7 @@ enum class CanvasImageSourceUsability {
     Good,
 };
 
-DOM::ExceptionOr<CanvasImageSourceUsability> check_usability_of_image(CanvasImageSource const&);
+WebIDL::ExceptionOr<CanvasImageSourceUsability> check_usability_of_image(CanvasImageSource const&);
 bool image_is_not_origin_clean(CanvasImageSource const&);
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/DOMParser.cpp b/Userland/Libraries/LibWeb/HTML/DOMParser.cpp
index f55851c757..bd4db0052f 100644
--- a/Userland/Libraries/LibWeb/HTML/DOMParser.cpp
+++ b/Userland/Libraries/LibWeb/HTML/DOMParser.cpp
@@ -13,7 +13,7 @@
 
 namespace Web::HTML {
 
-DOM::ExceptionOr<JS::NonnullGCPtr<DOMParser>> DOMParser::create_with_global_object(HTML::Window& window)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<DOMParser>> DOMParser::create_with_global_object(HTML::Window& window)
 {
     return JS::NonnullGCPtr(*window.heap().allocate<DOMParser>(window.realm(), window));
 }
diff --git a/Userland/Libraries/LibWeb/HTML/DOMParser.h b/Userland/Libraries/LibWeb/HTML/DOMParser.h
index 3f61c2c713..8ae6f70f6d 100644
--- a/Userland/Libraries/LibWeb/HTML/DOMParser.h
+++ b/Userland/Libraries/LibWeb/HTML/DOMParser.h
@@ -8,8 +8,8 @@
 
 #include <LibWeb/Bindings/PlatformObject.h>
 #include <LibWeb/DOM/Document.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -18,7 +18,7 @@ class DOMParser final : public Bindings::PlatformObject {
     WEB_PLATFORM_OBJECT(DOMParser, Bindings::PlatformObject);
 
 public:
-    static DOM::ExceptionOr<JS::NonnullGCPtr<DOMParser>> create_with_global_object(HTML::Window&);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<DOMParser>> create_with_global_object(HTML::Window&);
 
     virtual ~DOMParser() override;
 
diff --git a/Userland/Libraries/LibWeb/HTML/DOMStringMap.cpp b/Userland/Libraries/LibWeb/HTML/DOMStringMap.cpp
index 2db4c8512d..79456fbc97 100644
--- a/Userland/Libraries/LibWeb/HTML/DOMStringMap.cpp
+++ b/Userland/Libraries/LibWeb/HTML/DOMStringMap.cpp
@@ -111,7 +111,7 @@ String DOMStringMap::determine_value_of_named_property(String const& name) const
 }
 
 // https://html.spec.whatwg.org/multipage/dom.html#dom-domstringmap-setitem
-DOM::ExceptionOr<void> DOMStringMap::set_value_of_new_named_property(String const& name, String const& value)
+WebIDL::ExceptionOr<void> DOMStringMap::set_value_of_new_named_property(String const& name, String const& value)
 {
     AK::StringBuilder builder;
 
@@ -150,7 +150,7 @@ DOM::ExceptionOr<void> DOMStringMap::set_value_of_new_named_property(String cons
 }
 
 // https://html.spec.whatwg.org/multipage/dom.html#dom-domstringmap-setitem
-DOM::ExceptionOr<void> DOMStringMap::set_value_of_existing_named_property(String const& name, String const& value)
+WebIDL::ExceptionOr<void> DOMStringMap::set_value_of_existing_named_property(String const& name, String const& value)
 {
     return set_value_of_new_named_property(name, value);
 }
diff --git a/Userland/Libraries/LibWeb/HTML/DOMStringMap.h b/Userland/Libraries/LibWeb/HTML/DOMStringMap.h
index 34b5af5d88..2b98b53f23 100644
--- a/Userland/Libraries/LibWeb/HTML/DOMStringMap.h
+++ b/Userland/Libraries/LibWeb/HTML/DOMStringMap.h
@@ -25,8 +25,8 @@ public:
 
     String determine_value_of_named_property(String const&) const;
 
-    DOM::ExceptionOr<void> set_value_of_new_named_property(String const&, String const&);
-    DOM::ExceptionOr<void> set_value_of_existing_named_property(String const&, String const&);
+    WebIDL::ExceptionOr<void> set_value_of_new_named_property(String const&, String const&);
+    WebIDL::ExceptionOr<void> set_value_of_existing_named_property(String const&, String const&);
 
     bool delete_existing_named_property(String const&);
 
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
index 6f12735db7..3513098adc 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
@@ -9,7 +9,6 @@
 #include <LibJS/Parser.h>
 #include <LibWeb/DOM/DOMException.h>
 #include <LibWeb/DOM/Document.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/IDLEventListener.h>
 #include <LibWeb/HTML/BrowsingContext.h>
 #include <LibWeb/HTML/BrowsingContextContainer.h>
@@ -25,6 +24,7 @@
 #include <LibWeb/UIEvents/EventNames.h>
 #include <LibWeb/UIEvents/FocusEvent.h>
 #include <LibWeb/UIEvents/MouseEvent.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -90,7 +90,7 @@ String HTMLElement::content_editable() const
 }
 
 // https://html.spec.whatwg.org/multipage/interaction.html#contenteditable
-DOM::ExceptionOr<void> HTMLElement::set_content_editable(String const& content_editable)
+WebIDL::ExceptionOr<void> HTMLElement::set_content_editable(String const& content_editable)
 {
     if (content_editable.equals_ignoring_case("inherit"sv)) {
         remove_attribute(HTML::AttributeNames::contenteditable);
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLElement.h b/Userland/Libraries/LibWeb/HTML/HTMLElement.h
index 972a7cc178..68fdb4c1ff 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLElement.h
@@ -25,7 +25,7 @@ public:
 
     virtual bool is_editable() const final;
     String content_editable() const;
-    DOM::ExceptionOr<void> set_content_editable(String const&);
+    WebIDL::ExceptionOr<void> set_content_editable(String const&);
 
     String inner_text();
     void set_inner_text(StringView);
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.cpp b/Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.cpp
index ac7add85e2..086560a297 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.cpp
@@ -27,7 +27,7 @@ HTMLOptionsCollection::HTMLOptionsCollection(DOM::ParentNode& root, Function<boo
 HTMLOptionsCollection::~HTMLOptionsCollection() = default;
 
 // https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#dom-htmloptionscollection-add
-DOM::ExceptionOr<void> HTMLOptionsCollection::add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before)
+WebIDL::ExceptionOr<void> HTMLOptionsCollection::add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before)
 {
     auto resolved_element = element.visit(
         [](auto& e) -> JS::Handle<HTMLElement> {
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.h b/Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.h
index 7fa5d85ed8..813b202ded 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.h
@@ -7,8 +7,8 @@
 #pragma once
 
 #include <AK/Variant.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/HTMLCollection.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -22,7 +22,7 @@ public:
     static JS::NonnullGCPtr<HTMLOptionsCollection> create(DOM::ParentNode& root, Function<bool(DOM::Element const&)> filter);
     virtual ~HTMLOptionsCollection() override;
 
-    DOM::ExceptionOr<void> add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before = {});
+    WebIDL::ExceptionOr<void> add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before = {});
 
 private:
     HTMLOptionsCollection(DOM::ParentNode& root, Function<bool(DOM::Element const&)> filter);
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLSelectElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLSelectElement.cpp
index 534e75225d..6671dd26b6 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLSelectElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLSelectElement.cpp
@@ -43,7 +43,7 @@ JS::GCPtr<HTMLOptionsCollection> const& HTMLSelectElement::options()
 }
 
 // https://html.spec.whatwg.org/multipage/form-elements.html#dom-select-add
-DOM::ExceptionOr<void> HTMLSelectElement::add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before)
+WebIDL::ExceptionOr<void> HTMLSelectElement::add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before)
 {
     // Similarly, the add(element, before) method must act like its namesake method on that same options collection.
     return const_cast<HTMLOptionsCollection&>(*options()).add(move(element), move(before));
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLSelectElement.h b/Userland/Libraries/LibWeb/HTML/HTMLSelectElement.h
index a8ab71b15a..3e66c8d176 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLSelectElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLSelectElement.h
@@ -25,7 +25,7 @@ public:
 
     JS::GCPtr<HTMLOptionsCollection> const& options();
 
-    DOM::ExceptionOr<void> add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before = {});
+    WebIDL::ExceptionOr<void> add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before = {});
 
     int selected_index() const;
     void set_selected_index(int);
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp
index aacc49517b..a200f91391 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp
@@ -97,7 +97,7 @@ JS::GCPtr<HTMLTableSectionElement> HTMLTableElement::t_head()
     return nullptr;
 }
 
-DOM::ExceptionOr<void> HTMLTableElement::set_t_head(HTMLTableSectionElement* thead)
+WebIDL::ExceptionOr<void> HTMLTableElement::set_t_head(HTMLTableSectionElement* thead)
 {
     // FIXME: This is not always the case, but this function is currently written in a way that assumes non-null.
     VERIFY(thead);
@@ -184,7 +184,7 @@ JS::GCPtr<HTMLTableSectionElement> HTMLTableElement::t_foot()
     return nullptr;
 }
 
-DOM::ExceptionOr<void> HTMLTableElement::set_t_foot(HTMLTableSectionElement* tfoot)
+WebIDL::ExceptionOr<void> HTMLTableElement::set_t_foot(HTMLTableSectionElement* tfoot)
 {
     // FIXME: This is not always the case, but this function is currently written in a way that assumes non-null.
     VERIFY(tfoot);
@@ -280,7 +280,7 @@ JS::NonnullGCPtr<DOM::HTMLCollection> HTMLTableElement::rows()
     });
 }
 
-DOM::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> HTMLTableElement::insert_row(long index)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> HTMLTableElement::insert_row(long index)
 {
     auto rows = this->rows();
     auto rows_length = rows->length();
@@ -306,7 +306,7 @@ DOM::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> HTMLTableElement::insert
 }
 
 // https://html.spec.whatwg.org/multipage/tables.html#dom-table-deleterow
-DOM::ExceptionOr<void> HTMLTableElement::delete_row(long index)
+WebIDL::ExceptionOr<void> HTMLTableElement::delete_row(long index)
 {
     auto rows = this->rows();
     auto rows_length = rows->length();
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLTableElement.h b/Userland/Libraries/LibWeb/HTML/HTMLTableElement.h
index 23df8a9f1e..e18dd4058b 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLTableElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLTableElement.h
@@ -6,11 +6,11 @@
 
 #pragma once
 
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/HTML/HTMLElement.h>
 #include <LibWeb/HTML/HTMLTableCaptionElement.h>
 #include <LibWeb/HTML/HTMLTableRowElement.h>
 #include <LibWeb/HTML/HTMLTableSectionElement.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -26,12 +26,12 @@ public:
     void delete_caption();
 
     JS::GCPtr<HTMLTableSectionElement> t_head();
-    DOM::ExceptionOr<void> set_t_head(HTMLTableSectionElement* thead);
+    WebIDL::ExceptionOr<void> set_t_head(HTMLTableSectionElement* thead);
     JS::NonnullGCPtr<HTMLTableSectionElement> create_t_head();
     void delete_t_head();
 
     JS::GCPtr<HTMLTableSectionElement> t_foot();
-    DOM::ExceptionOr<void> set_t_foot(HTMLTableSectionElement* tfoot);
+    WebIDL::ExceptionOr<void> set_t_foot(HTMLTableSectionElement* tfoot);
     JS::NonnullGCPtr<HTMLTableSectionElement> create_t_foot();
     void delete_t_foot();
 
@@ -39,8 +39,8 @@ public:
     JS::NonnullGCPtr<HTMLTableSectionElement> create_t_body();
 
     JS::NonnullGCPtr<DOM::HTMLCollection> rows();
-    DOM::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> insert_row(long index);
-    DOM::ExceptionOr<void> delete_row(long index);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> insert_row(long index);
+    WebIDL::ExceptionOr<void> delete_row(long index);
 
 private:
     HTMLTableElement(DOM::Document&, DOM::QualifiedName);
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLTableSectionElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLTableSectionElement.cpp
index d0f4f04d22..39efff51ec 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLTableSectionElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLTableSectionElement.cpp
@@ -36,7 +36,7 @@ JS::NonnullGCPtr<DOM::HTMLCollection> HTMLTableSectionElement::rows() const
 }
 
 // https://html.spec.whatwg.org/multipage/tables.html#dom-tbody-insertrow
-DOM::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> HTMLTableSectionElement::insert_row(long index)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> HTMLTableSectionElement::insert_row(long index)
 {
     auto rows_collection = rows();
     auto rows_collection_size = static_cast<long>(rows_collection->length());
@@ -60,7 +60,7 @@ DOM::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> HTMLTableSectionElement:
 }
 
 // https://html.spec.whatwg.org/multipage/tables.html#dom-tbody-deleterow
-DOM::ExceptionOr<void> HTMLTableSectionElement::delete_row(long index)
+WebIDL::ExceptionOr<void> HTMLTableSectionElement::delete_row(long index)
 {
     auto rows_collection = rows();
     auto rows_collection_size = static_cast<long>(rows_collection->length());
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLTableSectionElement.h b/Userland/Libraries/LibWeb/HTML/HTMLTableSectionElement.h
index c41170b077..0965cdef89 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLTableSectionElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLTableSectionElement.h
@@ -18,8 +18,8 @@ public:
     virtual ~HTMLTableSectionElement() override;
 
     JS::NonnullGCPtr<DOM::HTMLCollection> rows() const;
-    DOM::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> insert_row(long index);
-    DOM::ExceptionOr<void> delete_row(long index);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<HTMLTableRowElement>> insert_row(long index);
+    WebIDL::ExceptionOr<void> delete_row(long index);
 
 private:
     HTMLTableSectionElement(DOM::Document&, DOM::QualifiedName);
diff --git a/Userland/Libraries/LibWeb/HTML/History.cpp b/Userland/Libraries/LibWeb/HTML/History.cpp
index e46b713f65..fa579167c7 100644
--- a/Userland/Libraries/LibWeb/HTML/History.cpp
+++ b/Userland/Libraries/LibWeb/HTML/History.cpp
@@ -30,21 +30,21 @@ void History::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://html.spec.whatwg.org/multipage/history.html#dom-history-pushstate
-DOM::ExceptionOr<void> History::push_state(JS::Value data, String const&, String const& url)
+WebIDL::ExceptionOr<void> History::push_state(JS::Value data, String const&, String const& url)
 {
     // NOTE: The second parameter of this function is intentionally unused.
     return shared_history_push_replace_state(data, url, IsPush::Yes);
 }
 
 // https://html.spec.whatwg.org/multipage/history.html#dom-history-replacestate
-DOM::ExceptionOr<void> History::replace_state(JS::Value data, String const&, String const& url)
+WebIDL::ExceptionOr<void> History::replace_state(JS::Value data, String const&, String const& url)
 {
     // NOTE: The second parameter of this function is intentionally unused.
     return shared_history_push_replace_state(data, url, IsPush::No);
 }
 
 // https://html.spec.whatwg.org/multipage/history.html#shared-history-push/replace-state-steps
-DOM::ExceptionOr<void> History::shared_history_push_replace_state(JS::Value, String const&, IsPush)
+WebIDL::ExceptionOr<void> History::shared_history_push_replace_state(JS::Value, String const&, IsPush)
 {
     // 1. Let document be history's associated Document. (NOTE: Not necessary)
 
diff --git a/Userland/Libraries/LibWeb/HTML/History.h b/Userland/Libraries/LibWeb/HTML/History.h
index 55ab0a2675..b7d22ef12c 100644
--- a/Userland/Libraries/LibWeb/HTML/History.h
+++ b/Userland/Libraries/LibWeb/HTML/History.h
@@ -9,7 +9,7 @@
 
 #include <LibJS/Heap/Handle.h>
 #include <LibWeb/Bindings/PlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -21,8 +21,8 @@ public:
 
     virtual ~History() override;
 
-    DOM::ExceptionOr<void> push_state(JS::Value data, String const& unused, String const& url);
-    DOM::ExceptionOr<void> replace_state(JS::Value data, String const& unused, String const& url);
+    WebIDL::ExceptionOr<void> push_state(JS::Value data, String const& unused, String const& url);
+    WebIDL::ExceptionOr<void> replace_state(JS::Value data, String const& unused, String const& url);
 
 private:
     explicit History(HTML::Window&, DOM::Document&);
@@ -33,7 +33,7 @@ private:
         No,
         Yes,
     };
-    DOM::ExceptionOr<void> shared_history_push_replace_state(JS::Value data, String const& url, IsPush is_push);
+    WebIDL::ExceptionOr<void> shared_history_push_replace_state(JS::Value data, String const& url, IsPush is_push);
 
     JS::NonnullGCPtr<DOM::Document> m_associated_document;
 };
diff --git a/Userland/Libraries/LibWeb/HTML/Storage.cpp b/Userland/Libraries/LibWeb/HTML/Storage.cpp
index dc4855a04f..7db1d4a554 100644
--- a/Userland/Libraries/LibWeb/HTML/Storage.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Storage.cpp
@@ -57,7 +57,7 @@ String Storage::get_item(String const& key) const
 }
 
 // https://html.spec.whatwg.org/multipage/webstorage.html#dom-storage-setitem
-DOM::ExceptionOr<void> Storage::set_item(String const& key, String const& value)
+WebIDL::ExceptionOr<void> Storage::set_item(String const& key, String const& value)
 {
     // 1. Let oldValue be null.
     String old_value;
diff --git a/Userland/Libraries/LibWeb/HTML/Storage.h b/Userland/Libraries/LibWeb/HTML/Storage.h
index 890023fa5b..409d511949 100644
--- a/Userland/Libraries/LibWeb/HTML/Storage.h
+++ b/Userland/Libraries/LibWeb/HTML/Storage.h
@@ -8,7 +8,7 @@
 
 #include <AK/HashMap.h>
 #include <LibWeb/Bindings/PlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -22,7 +22,7 @@ public:
     size_t length() const;
     String key(size_t index);
     String get_item(String const& key) const;
-    DOM::ExceptionOr<void> set_item(String const& key, String const& value);
+    WebIDL::ExceptionOr<void> set_item(String const& key, String const& value);
     void remove_item(String const& key);
     void clear();
 
diff --git a/Userland/Libraries/LibWeb/HTML/Window.cpp b/Userland/Libraries/LibWeb/HTML/Window.cpp
index 297a5a42b6..f21ec41059 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Window.cpp
@@ -596,7 +596,7 @@ Window* Window::parent()
 }
 
 // https://html.spec.whatwg.org/multipage/web-messaging.html#window-post-message-steps
-DOM::ExceptionOr<void> Window::post_message_impl(JS::Value message, String const&)
+WebIDL::ExceptionOr<void> Window::post_message_impl(JS::Value message, String const&)
 {
     // FIXME: This is an ad-hoc hack implementation instead, since we don't currently
     //        have serialization and deserialization of messages.
diff --git a/Userland/Libraries/LibWeb/HTML/Window.h b/Userland/Libraries/LibWeb/HTML/Window.h
index 16e0799415..0f9c09e464 100644
--- a/Userland/Libraries/LibWeb/HTML/Window.h
+++ b/Userland/Libraries/LibWeb/HTML/Window.h
@@ -108,7 +108,7 @@ public:
 
     Window* parent();
 
-    DOM::ExceptionOr<void> post_message_impl(JS::Value, String const& target_origin);
+    WebIDL::ExceptionOr<void> post_message_impl(JS::Value, String const& target_origin);
 
     String name() const;
     void set_name(String const&);
diff --git a/Userland/Libraries/LibWeb/HTML/Worker.cpp b/Userland/Libraries/LibWeb/HTML/Worker.cpp
index d8c4dc9c53..7797b28ff5 100644
--- a/Userland/Libraries/LibWeb/HTML/Worker.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Worker.cpp
@@ -8,10 +8,10 @@
 #include <LibJS/Runtime/ConsoleObject.h>
 #include <LibJS/Runtime/Realm.h>
 #include <LibWeb/Bindings/MainThreadVM.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/HTML/Scripting/Environments.h>
 #include <LibWeb/HTML/Worker.h>
 #include <LibWeb/HTML/WorkerDebugConsoleClient.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::HTML {
 
@@ -39,7 +39,7 @@ void Worker::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://html.spec.whatwg.org/multipage/workers.html#dom-worker
-DOM::ExceptionOr<JS::NonnullGCPtr<Worker>> Worker::create(FlyString const& script_url, WorkerOptions const options, DOM::Document& document)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Worker>> Worker::create(FlyString const& script_url, WorkerOptions const options, DOM::Document& document)
 {
     dbgln_if(WEB_WORKER_DEBUG, "WebWorker: Creating worker with script_url = {}", script_url);
 
@@ -312,7 +312,7 @@ void Worker::run_a_worker(AK::URL& url, EnvironmentSettingsObject& outside_setti
 }
 
 // https://html.spec.whatwg.org/multipage/workers.html#dom-worker-terminate
-DOM::ExceptionOr<void> Worker::terminate()
+WebIDL::ExceptionOr<void> Worker::terminate()
 {
     dbgln_if(WEB_WORKER_DEBUG, "WebWorker: Terminate");
 
diff --git a/Userland/Libraries/LibWeb/HTML/Worker.h b/Userland/Libraries/LibWeb/HTML/Worker.h
index bcc1a447bd..d3c92d616b 100644
--- a/Userland/Libraries/LibWeb/HTML/Worker.h
+++ b/Userland/Libraries/LibWeb/HTML/Worker.h
@@ -36,13 +36,13 @@ class Worker : public DOM::EventTarget {
     WEB_PLATFORM_OBJECT(Worker, DOM::EventTarget);
 
 public:
-    static DOM::ExceptionOr<JS::NonnullGCPtr<Worker>> create(FlyString const& script_url, WorkerOptions const options, DOM::Document& document);
-    static DOM::ExceptionOr<JS::NonnullGCPtr<Worker>> create_with_global_object(HTML::Window& window, FlyString const& script_url, WorkerOptions const options)
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<Worker>> create(FlyString const& script_url, WorkerOptions const options, DOM::Document& document);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<Worker>> create_with_global_object(HTML::Window& window, FlyString const& script_url, WorkerOptions const options)
     {
         return Worker::create(script_url, options, window.associated_document());
     }
 
-    DOM::ExceptionOr<void> terminate();
+    WebIDL::ExceptionOr<void> terminate();
 
     void post_message(JS::Value message, JS::Value transfer);
 
diff --git a/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.cpp b/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.cpp
index 93d4e39827..93f929fca4 100644
--- a/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.cpp
+++ b/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.cpp
@@ -43,7 +43,7 @@ void WorkerGlobalScope::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://html.spec.whatwg.org/multipage/workers.html#importing-scripts-and-libraries
-DOM::ExceptionOr<void> WorkerGlobalScope::import_scripts(Vector<String> urls)
+WebIDL::ExceptionOr<void> WorkerGlobalScope::import_scripts(Vector<String> urls)
 {
     // The algorithm may optionally be customized by supplying custom perform the fetch hooks,
     // which if provided will be used when invoking fetch a classic worker-imported script.
@@ -121,7 +121,7 @@ bool WorkerGlobalScope::cross_origin_isolated() const
 }
 
 // https://html.spec.whatwg.org/multipage/webappapis.html#dom-btoa
-DOM::ExceptionOr<String> WorkerGlobalScope::btoa(String const& data) const
+WebIDL::ExceptionOr<String> WorkerGlobalScope::btoa(String const& data) const
 {
     // FIXME: This is the same as the implementation in Bindings/WindowObject.cpp
     //     Find a way to share this implementation, since they come from the same mixin.
@@ -141,7 +141,7 @@ DOM::ExceptionOr<String> WorkerGlobalScope::btoa(String const& data) const
 }
 
 // https://html.spec.whatwg.org/multipage/webappapis.html#dom-atob
-DOM::ExceptionOr<String> WorkerGlobalScope::atob(String const& data) const
+WebIDL::ExceptionOr<String> WorkerGlobalScope::atob(String const& data) const
 {
     // FIXME: This is the same as the implementation in Bindings/WindowObject.cpp
     //     Find a way to share this implementation, since they come from the same mixin.
diff --git a/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.h b/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.h
index 66d571f1d1..2d7dee7e36 100644
--- a/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.h
+++ b/Userland/Libraries/LibWeb/HTML/WorkerGlobalScope.h
@@ -10,10 +10,10 @@
 #include <AK/RefCounted.h>
 #include <AK/URL.h>
 #include <LibWeb/DOM/EventTarget.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
 #include <LibWeb/HTML/WorkerLocation.h>
 #include <LibWeb/HTML/WorkerNavigator.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 #define ENUMERATE_WORKER_GLOBAL_SCOPE_EVENT_HANDLERS(E)       \
     E(onerror, HTML::EventNames::error)                       \
@@ -42,7 +42,7 @@ public:
 
     JS::NonnullGCPtr<WorkerLocation> location() const;
     JS::NonnullGCPtr<WorkerNavigator> navigator() const;
-    DOM::ExceptionOr<void> import_scripts(Vector<String> urls);
+    WebIDL::ExceptionOr<void> import_scripts(Vector<String> urls);
 
 #undef __ENUMERATE
 #define __ENUMERATE(attribute_name, event_name)       \
@@ -57,8 +57,8 @@ public:
     String origin() const;
     bool is_secure_context() const;
     bool cross_origin_isolated() const;
-    DOM::ExceptionOr<String> btoa(String const& data) const;
-    DOM::ExceptionOr<String> atob(String const& data) const;
+    WebIDL::ExceptionOr<String> btoa(String const& data) const;
+    WebIDL::ExceptionOr<String> atob(String const& data) const;
 
     // Non-IDL public methods
 
diff --git a/Userland/Libraries/LibWeb/SVG/SVGLength.cpp b/Userland/Libraries/LibWeb/SVG/SVGLength.cpp
index b84073c281..cc9df8c642 100644
--- a/Userland/Libraries/LibWeb/SVG/SVGLength.cpp
+++ b/Userland/Libraries/LibWeb/SVG/SVGLength.cpp
@@ -25,7 +25,7 @@ SVGLength::SVGLength(HTML::Window& window, u8 unit_type, float value)
 SVGLength::~SVGLength() = default;
 
 // https://www.w3.org/TR/SVG11/types.html#__svg__SVGLength__value
-DOM::ExceptionOr<void> SVGLength::set_value(float value)
+WebIDL::ExceptionOr<void> SVGLength::set_value(float value)
 {
     // FIXME: Raise an exception if this <length> is read-only.
     m_value = value;
diff --git a/Userland/Libraries/LibWeb/SVG/SVGLength.h b/Userland/Libraries/LibWeb/SVG/SVGLength.h
index bd6c90d110..fac3a8cf0a 100644
--- a/Userland/Libraries/LibWeb/SVG/SVGLength.h
+++ b/Userland/Libraries/LibWeb/SVG/SVGLength.h
@@ -7,7 +7,7 @@
 #pragma once
 
 #include <LibWeb/Bindings/PlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::SVG {
 
@@ -22,7 +22,7 @@ public:
     u8 unit_type() const { return m_unit_type; }
 
     float value() const { return m_value; }
-    DOM::ExceptionOr<void> set_value(float value);
+    WebIDL::ExceptionOr<void> set_value(float value);
 
 private:
     SVGLength(HTML::Window&, u8 unit_type, float value);
diff --git a/Userland/Libraries/LibWeb/Streams/ReadableStream.cpp b/Userland/Libraries/LibWeb/Streams/ReadableStream.cpp
index e035a96b3e..eeaa7efaa5 100644
--- a/Userland/Libraries/LibWeb/Streams/ReadableStream.cpp
+++ b/Userland/Libraries/LibWeb/Streams/ReadableStream.cpp
@@ -11,7 +11,7 @@
 namespace Web::Streams {
 
 // https://streams.spec.whatwg.org/#rs-constructor
-DOM::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> ReadableStream::create_with_global_object(HTML::Window& window)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> ReadableStream::create_with_global_object(HTML::Window& window)
 {
     auto* readable_stream = window.heap().allocate<ReadableStream>(window.realm(), window);
 
diff --git a/Userland/Libraries/LibWeb/Streams/ReadableStream.h b/Userland/Libraries/LibWeb/Streams/ReadableStream.h
index 7a60125e89..94f89096f2 100644
--- a/Userland/Libraries/LibWeb/Streams/ReadableStream.h
+++ b/Userland/Libraries/LibWeb/Streams/ReadableStream.h
@@ -24,7 +24,7 @@ public:
         Errored,
     };
 
-    static DOM::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> create_with_global_object(HTML::Window&);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<ReadableStream>> create_with_global_object(HTML::Window&);
 
     virtual ~ReadableStream() override;
 
diff --git a/Userland/Libraries/LibWeb/URL/URL.cpp b/Userland/Libraries/LibWeb/URL/URL.cpp
index 882f3c1e2a..9302c0f818 100644
--- a/Userland/Libraries/LibWeb/URL/URL.cpp
+++ b/Userland/Libraries/LibWeb/URL/URL.cpp
@@ -16,7 +16,7 @@ JS::NonnullGCPtr<URL> URL::create(HTML::Window& window, AK::URL url, JS::Nonnull
     return *window.heap().allocate<URL>(window.realm(), window, move(url), move(query));
 }
 
-DOM::ExceptionOr<JS::NonnullGCPtr<URL>> URL::create_with_global_object(HTML::Window& window, String const& url, String const& base)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<URL>> URL::create_with_global_object(HTML::Window& window, String const& url, String const& base)
 {
     // 1. Let parsedBase be null.
     Optional<AK::URL> parsed_base;
@@ -26,7 +26,7 @@ DOM::ExceptionOr<JS::NonnullGCPtr<URL>> URL::create_with_global_object(HTML::Win
         parsed_base = base;
         // 2. If parsedBase is failure, then throw a TypeError.
         if (!parsed_base->is_valid())
-            return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid base URL" };
+            return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid base URL" };
     }
     // 3. Let parsedURL be the result of running the basic URL parser on url with parsedBase.
     AK::URL parsed_url;
@@ -36,7 +36,7 @@ DOM::ExceptionOr<JS::NonnullGCPtr<URL>> URL::create_with_global_object(HTML::Win
         parsed_url = url;
     // 4. If parsedURL is failure, then throw a TypeError.
     if (!parsed_url.is_valid())
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid URL" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid URL" };
     // 5. Let query be parsedURL’s query, if that is non-null, and the empty string otherwise.
     auto& query = parsed_url.query().is_null() ? String::empty() : parsed_url.query();
     // 6. Set this’s URL to parsedURL.
@@ -78,13 +78,13 @@ String URL::to_json() const
     return m_url.serialize();
 }
 
-DOM::ExceptionOr<void> URL::set_href(String const& href)
+WebIDL::ExceptionOr<void> URL::set_href(String const& href)
 {
     // 1. Let parsedURL be the result of running the basic URL parser on the given value.
     AK::URL parsed_url = href;
     // 2. If parsedURL is failure, then throw a TypeError.
     if (!parsed_url.is_valid())
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid URL" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Invalid URL" };
     // 3. Set this’s URL to parsedURL.
     m_url = move(parsed_url);
     // 4. Empty this’s query object’s list.
diff --git a/Userland/Libraries/LibWeb/URL/URL.h b/Userland/Libraries/LibWeb/URL/URL.h
index ce23f6ea9e..849a51871b 100644
--- a/Userland/Libraries/LibWeb/URL/URL.h
+++ b/Userland/Libraries/LibWeb/URL/URL.h
@@ -10,8 +10,8 @@
 #include <AK/String.h>
 #include <AK/URL.h>
 #include <LibWeb/Bindings/PlatformObject.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/URL/URLSearchParams.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::URL {
 
@@ -20,12 +20,12 @@ class URL : public Bindings::PlatformObject {
 
 public:
     static JS::NonnullGCPtr<URL> create(HTML::Window&, AK::URL url, JS::NonnullGCPtr<URLSearchParams> query);
-    static DOM::ExceptionOr<JS::NonnullGCPtr<URL>> create_with_global_object(HTML::Window&, String const& url, String const& base);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<URL>> create_with_global_object(HTML::Window&, String const& url, String const& base);
 
     virtual ~URL() override;
 
     String href() const;
-    DOM::ExceptionOr<void> set_href(String const&);
+    WebIDL::ExceptionOr<void> set_href(String const&);
 
     String origin() const;
 
diff --git a/Userland/Libraries/LibWeb/URL/URLSearchParams.cpp b/Userland/Libraries/LibWeb/URL/URLSearchParams.cpp
index 511e6f878f..ef12b26927 100644
--- a/Userland/Libraries/LibWeb/URL/URLSearchParams.cpp
+++ b/Userland/Libraries/LibWeb/URL/URLSearchParams.cpp
@@ -89,7 +89,7 @@ JS::NonnullGCPtr<URLSearchParams> URLSearchParams::create(HTML::Window& window,
 
 // https://url.spec.whatwg.org/#dom-urlsearchparams-urlsearchparams
 // https://url.spec.whatwg.org/#urlsearchparams-initialize
-DOM::ExceptionOr<JS::NonnullGCPtr<URLSearchParams>> URLSearchParams::create_with_global_object(HTML::Window& window, Variant<Vector<Vector<String>>, OrderedHashMap<String, String>, String> const& init)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<URLSearchParams>> URLSearchParams::create_with_global_object(HTML::Window& window, Variant<Vector<Vector<String>>, OrderedHashMap<String, String>, String> const& init)
 {
     // 1. If init is a string and starts with U+003F (?), then remove the first code point from init.
     // NOTE: We do this when we know that it's a string on step 3 of initialization.
@@ -108,7 +108,7 @@ DOM::ExceptionOr<JS::NonnullGCPtr<URLSearchParams>> URLSearchParams::create_with
         for (auto const& pair : init_sequence) {
             // a. If pair does not contain exactly two items, then throw a TypeError.
             if (pair.size() != 2)
-                return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, String::formatted("Expected only 2 items in pair, got {}", pair.size()) };
+                return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, String::formatted("Expected only 2 items in pair, got {}", pair.size()) };
 
             // b. Append a new name-value pair whose name is pair’s first item, and value is pair’s second item, to query’s list.
             list.append(QueryParam { .name = pair[0], .value = pair[1] });
diff --git a/Userland/Libraries/LibWeb/URL/URLSearchParams.h b/Userland/Libraries/LibWeb/URL/URLSearchParams.h
index ea1737e4d6..97413dcb6b 100644
--- a/Userland/Libraries/LibWeb/URL/URLSearchParams.h
+++ b/Userland/Libraries/LibWeb/URL/URLSearchParams.h
@@ -8,7 +8,7 @@
 
 #include <AK/URL.h>
 #include <AK/Vector.h>
-#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::URL {
 
@@ -24,7 +24,7 @@ class URLSearchParams : public Bindings::PlatformObject {
 
 public:
     static JS::NonnullGCPtr<URLSearchParams> create(HTML::Window&, Vector<QueryParam> list);
-    static DOM::ExceptionOr<JS::NonnullGCPtr<URLSearchParams>> create_with_global_object(HTML::Window&, Variant<Vector<Vector<String>>, OrderedHashMap<String, String>, String> const& init);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<URLSearchParams>> create_with_global_object(HTML::Window&, Variant<Vector<Vector<String>>, OrderedHashMap<String, String>, String> const& init);
 
     virtual ~URLSearchParams() override;
 
diff --git a/Userland/Libraries/LibWeb/DOM/ExceptionOr.h b/Userland/Libraries/LibWeb/WebIDL/ExceptionOr.h
similarity index 76%
rename from Userland/Libraries/LibWeb/DOM/ExceptionOr.h
rename to Userland/Libraries/LibWeb/WebIDL/ExceptionOr.h
index 8e99b6adaf..23944eafa3 100644
--- a/Userland/Libraries/LibWeb/DOM/ExceptionOr.h
+++ b/Userland/Libraries/LibWeb/WebIDL/ExceptionOr.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Linus Groh <linusg@serenityos.org>
+ * Copyright (c) 2021-2022, Linus Groh <linusg@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -11,7 +11,7 @@
 #include <AK/RefPtr.h>
 #include <LibWeb/DOM/DOMException.h>
 
-namespace Web::DOM {
+namespace Web::WebIDL {
 
 #define ENUMERATE_SIMPLE_WEBIDL_EXCEPTION_TYPES(E) \
     E(EvalError)                                   \
@@ -49,7 +49,7 @@ public:
     {
     }
 
-    ExceptionOr(JS::NonnullGCPtr<DOMException> exception)
+    ExceptionOr(JS::NonnullGCPtr<DOM::DOMException> exception)
         : m_exception(move(exception))
     {
     }
@@ -59,8 +59,8 @@ public:
     {
     }
 
-    ExceptionOr(Variant<SimpleException, JS::NonnullGCPtr<DOMException>> exception)
-        : m_exception(move(exception).template downcast<Empty, SimpleException, JS::NonnullGCPtr<DOMException>>())
+    ExceptionOr(Variant<SimpleException, JS::NonnullGCPtr<DOM::DOMException>> exception)
+        : m_exception(move(exception).template downcast<Empty, SimpleException, JS::NonnullGCPtr<DOM::DOMException>>())
     {
     }
 
@@ -78,9 +78,9 @@ public:
         return m_result.release_value();
     }
 
-    Variant<SimpleException, JS::NonnullGCPtr<DOMException>> exception() const
+    Variant<SimpleException, JS::NonnullGCPtr<DOM::DOMException>> exception() const
     {
-        return m_exception.template downcast<SimpleException, JS::NonnullGCPtr<DOMException>>();
+        return m_exception.template downcast<SimpleException, JS::NonnullGCPtr<DOM::DOMException>>();
     }
 
     bool is_exception() const
@@ -90,12 +90,13 @@ public:
 
     // These are for compatibility with the TRY() macro in AK.
     [[nodiscard]] bool is_error() const { return is_exception(); }
-    Variant<SimpleException, JS::NonnullGCPtr<DOMException>> release_error() { return exception(); }
+    Variant<SimpleException, JS::NonnullGCPtr<DOM::DOMException>> release_error() { return exception(); }
 
 private:
     Optional<ValueType> m_result;
+
     // https://webidl.spec.whatwg.org/#idl-exceptions
-    Variant<Empty, SimpleException, JS::NonnullGCPtr<DOMException>> m_exception {};
+    Variant<Empty, SimpleException, JS::NonnullGCPtr<DOM::DOMException>> m_exception {};
 };
 
 template<>
diff --git a/Userland/Libraries/LibWeb/WebSockets/WebSocket.cpp b/Userland/Libraries/LibWeb/WebSockets/WebSocket.cpp
index ac2ccc0228..b429277aed 100644
--- a/Userland/Libraries/LibWeb/WebSockets/WebSocket.cpp
+++ b/Userland/Libraries/LibWeb/WebSockets/WebSocket.cpp
@@ -12,7 +12,6 @@
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Event.h>
 #include <LibWeb/DOM/EventDispatcher.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/IDLEventListener.h>
 #include <LibWeb/HTML/CloseEvent.h>
 #include <LibWeb/HTML/EventHandler.h>
@@ -20,6 +19,7 @@
 #include <LibWeb/HTML/MessageEvent.h>
 #include <LibWeb/HTML/Origin.h>
 #include <LibWeb/HTML/Window.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 #include <LibWeb/WebSockets/WebSocket.h>
 
 namespace Web::WebSockets {
@@ -47,7 +47,7 @@ WebSocketClientSocket::~WebSocketClientSocket() = default;
 WebSocketClientManager::WebSocketClientManager() = default;
 
 // https://websockets.spec.whatwg.org/#dom-websocket-websocket
-DOM::ExceptionOr<JS::NonnullGCPtr<WebSocket>> WebSocket::create_with_global_object(HTML::Window& window, String const& url)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<WebSocket>> WebSocket::create_with_global_object(HTML::Window& window, String const& url)
 {
     AK::URL url_record(url);
     if (!url_record.is_valid())
@@ -133,7 +133,7 @@ String WebSocket::protocol() const
 }
 
 // https://websockets.spec.whatwg.org/#dom-websocket-close
-DOM::ExceptionOr<void> WebSocket::close(Optional<u16> code, Optional<String> reason)
+WebIDL::ExceptionOr<void> WebSocket::close(Optional<u16> code, Optional<String> reason)
 {
     // 1. If code is present, but is neither an integer equal to 1000 nor an integer in the range 3000 to 4999, inclusive, throw an "InvalidAccessError" DOMException.
     if (code.has_value() && *code != 1000 && (*code < 3000 || *code > 4099))
@@ -160,7 +160,7 @@ DOM::ExceptionOr<void> WebSocket::close(Optional<u16> code, Optional<String> rea
 }
 
 // https://websockets.spec.whatwg.org/#dom-websocket-send
-DOM::ExceptionOr<void> WebSocket::send(String const& data)
+WebIDL::ExceptionOr<void> WebSocket::send(String const& data)
 {
     auto state = ready_state();
     if (state == WebSocket::ReadyState::Connecting)
diff --git a/Userland/Libraries/LibWeb/WebSockets/WebSocket.h b/Userland/Libraries/LibWeb/WebSockets/WebSocket.h
index bdfacd55cc..f882120f24 100644
--- a/Userland/Libraries/LibWeb/WebSockets/WebSocket.h
+++ b/Userland/Libraries/LibWeb/WebSockets/WebSocket.h
@@ -11,9 +11,9 @@
 #include <LibCore/Object.h>
 #include <LibWeb/Bindings/PlatformObject.h>
 #include <LibWeb/DOM/EventTarget.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Forward.h>
 #include <LibWeb/HTML/Window.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 #define ENUMERATE_WEBSOCKET_EVENT_HANDLERS(E) \
     E(onerror, HTML::EventNames::error)       \
@@ -37,7 +37,7 @@ public:
         Closed = 3,
     };
 
-    static DOM::ExceptionOr<JS::NonnullGCPtr<WebSocket>> create_with_global_object(HTML::Window&, String const& url);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<WebSocket>> create_with_global_object(HTML::Window&, String const& url);
 
     virtual ~WebSocket() override;
 
@@ -57,8 +57,8 @@ public:
     String const& binary_type() { return m_binary_type; };
     void set_binary_type(String const& type) { m_binary_type = type; };
 
-    DOM::ExceptionOr<void> close(Optional<u16> code, Optional<String> reason);
-    DOM::ExceptionOr<void> send(String const& data);
+    WebIDL::ExceptionOr<void> close(Optional<u16> code, Optional<String> reason);
+    WebIDL::ExceptionOr<void> send(String const& data);
 
 private:
     void on_open();
diff --git a/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp b/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
index db3b747d61..39516aba6b 100644
--- a/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
+++ b/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
@@ -21,7 +21,6 @@
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Event.h>
 #include <LibWeb/DOM/EventDispatcher.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/DOM/IDLEventListener.h>
 #include <LibWeb/Fetch/BodyInit.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP.h>
@@ -34,6 +33,7 @@
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/Loader/ResourceLoader.h>
 #include <LibWeb/Page/Page.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 #include <LibWeb/XHR/EventNames.h>
 #include <LibWeb/XHR/ProgressEvent.h>
 #include <LibWeb/XHR/XMLHttpRequest.h>
@@ -80,7 +80,7 @@ void XMLHttpRequest::fire_progress_event(String const& event_name, u64 transmitt
 }
 
 // https://xhr.spec.whatwg.org/#dom-xmlhttprequest-responsetext
-DOM::ExceptionOr<String> XMLHttpRequest::response_text() const
+WebIDL::ExceptionOr<String> XMLHttpRequest::response_text() const
 {
     // 1. If this’s response type is not the empty string or "text", then throw an "InvalidStateError" DOMException.
     if (m_response_type != Bindings::XMLHttpRequestResponseType::Empty && m_response_type != Bindings::XMLHttpRequestResponseType::Text)
@@ -94,7 +94,7 @@ DOM::ExceptionOr<String> XMLHttpRequest::response_text() const
 }
 
 // https://xhr.spec.whatwg.org/#response
-DOM::ExceptionOr<JS::Value> XMLHttpRequest::response()
+WebIDL::ExceptionOr<JS::Value> XMLHttpRequest::response()
 {
     // 1. If this’s response type is the empty string or "text", then:
     if (m_response_type == Bindings::XMLHttpRequestResponseType::Empty || m_response_type == Bindings::XMLHttpRequestResponseType::Text) {
@@ -139,7 +139,7 @@ DOM::ExceptionOr<JS::Value> XMLHttpRequest::response()
     // 7. Otherwise, if this’s response type is "document", set a document response for this.
     else if (m_response_type == Bindings::XMLHttpRequestResponseType::Document) {
         // FIXME: Implement this.
-        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "XHR Document type not implemented" };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "XHR Document type not implemented" };
     }
     // 8. Otherwise:
     else {
@@ -269,7 +269,7 @@ Optional<StringView> XMLHttpRequest::get_final_encoding() const
 }
 
 // https://xhr.spec.whatwg.org/#dom-xmlhttprequest-setrequestheader
-DOM::ExceptionOr<void> XMLHttpRequest::set_request_header(String const& name_string, String const& value_string)
+WebIDL::ExceptionOr<void> XMLHttpRequest::set_request_header(String const& name_string, String const& value_string)
 {
     auto name = name_string.to_byte_buffer();
     auto value = value_string.to_byte_buffer();
@@ -312,13 +312,13 @@ DOM::ExceptionOr<void> XMLHttpRequest::set_request_header(String const& name_str
 }
 
 // https://xhr.spec.whatwg.org/#dom-xmlhttprequest-open
-DOM::ExceptionOr<void> XMLHttpRequest::open(String const& method_string, String const& url)
+WebIDL::ExceptionOr<void> XMLHttpRequest::open(String const& method_string, String const& url)
 {
     // 8. If the async argument is omitted, set async to true, and set username and password to null.
     return open(method_string, url, true, {}, {});
 }
 
-DOM::ExceptionOr<void> XMLHttpRequest::open(String const& method_string, String const& url, bool async, String const& username, String const& password)
+WebIDL::ExceptionOr<void> XMLHttpRequest::open(String const& method_string, String const& url, bool async, String const& username, String const& password)
 {
     auto method = method_string.to_byte_buffer();
 
@@ -395,7 +395,7 @@ DOM::ExceptionOr<void> XMLHttpRequest::open(String const& method_string, String
 }
 
 // https://xhr.spec.whatwg.org/#dom-xmlhttprequest-send
-DOM::ExceptionOr<void> XMLHttpRequest::send(Optional<Fetch::XMLHttpRequestBodyInit> body)
+WebIDL::ExceptionOr<void> XMLHttpRequest::send(Optional<Fetch::XMLHttpRequestBodyInit> body)
 {
     auto& vm = this->vm();
     auto& realm = *vm.current_realm();
@@ -548,7 +548,7 @@ String XMLHttpRequest::get_all_response_headers() const
 }
 
 // https://xhr.spec.whatwg.org/#dom-xmlhttprequest-overridemimetype
-DOM::ExceptionOr<void> XMLHttpRequest::override_mime_type(String const& mime)
+WebIDL::ExceptionOr<void> XMLHttpRequest::override_mime_type(String const& mime)
 {
     // 1. If this’s state is loading or done, then throw an "InvalidStateError" DOMException.
     if (m_ready_state == ReadyState::Loading || m_ready_state == ReadyState::Done)
@@ -565,7 +565,7 @@ DOM::ExceptionOr<void> XMLHttpRequest::override_mime_type(String const& mime)
 }
 
 // https://xhr.spec.whatwg.org/#ref-for-dom-xmlhttprequest-timeout%E2%91%A2
-DOM::ExceptionOr<void> XMLHttpRequest::set_timeout(u32 timeout)
+WebIDL::ExceptionOr<void> XMLHttpRequest::set_timeout(u32 timeout)
 {
     // 1. If the current global object is a Window object and this’s synchronous flag is set,
     //    then throw an "InvalidAccessError" DOMException.
diff --git a/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.h b/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.h
index 1af8eae57b..d4127de532 100644
--- a/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.h
+++ b/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.h
@@ -12,13 +12,13 @@
 #include <AK/URL.h>
 #include <AK/Weakable.h>
 #include <LibWeb/DOM/EventTarget.h>
-#include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/Fetch/BodyInit.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Headers.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Statuses.h>
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/MimeSniff/MimeType.h>
 #include <LibWeb/URL/URLSearchParams.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 #include <LibWeb/XHR/XMLHttpRequestEventTarget.h>
 
 namespace Web::XHR {
@@ -41,15 +41,15 @@ public:
 
     ReadyState ready_state() const { return m_ready_state; };
     Fetch::Infrastructure::Status status() const { return m_status; };
-    DOM::ExceptionOr<String> response_text() const;
-    DOM::ExceptionOr<JS::Value> response();
+    WebIDL::ExceptionOr<String> response_text() const;
+    WebIDL::ExceptionOr<JS::Value> response();
     Bindings::XMLHttpRequestResponseType response_type() const { return m_response_type; }
 
-    DOM::ExceptionOr<void> open(String const& method, String const& url);
-    DOM::ExceptionOr<void> open(String const& method, String const& url, bool async, String const& username = {}, String const& password = {});
-    DOM::ExceptionOr<void> send(Optional<Fetch::XMLHttpRequestBodyInit> body);
+    WebIDL::ExceptionOr<void> open(String const& method, String const& url);
+    WebIDL::ExceptionOr<void> open(String const& method, String const& url, bool async, String const& username = {}, String const& password = {});
+    WebIDL::ExceptionOr<void> send(Optional<Fetch::XMLHttpRequestBodyInit> body);
 
-    DOM::ExceptionOr<void> set_request_header(String const& header, String const& value);
+    WebIDL::ExceptionOr<void> set_request_header(String const& header, String const& value);
     void set_response_type(Bindings::XMLHttpRequestResponseType type) { m_response_type = type; }
 
     String get_response_header(String const& name) { return m_response_headers.get(name).value_or({}); }
@@ -58,9 +58,9 @@ public:
     WebIDL::CallbackType* onreadystatechange();
     void set_onreadystatechange(WebIDL::CallbackType*);
 
-    DOM::ExceptionOr<void> override_mime_type(String const& mime);
+    WebIDL::ExceptionOr<void> override_mime_type(String const& mime);
 
-    DOM::ExceptionOr<void> set_timeout(u32 timeout);
+    WebIDL::ExceptionOr<void> set_timeout(u32 timeout);
     u32 timeout() const;
 
 private: