diff --git a/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp b/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
index d01cb7df65..01e24b2e84 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
+++ b/Userland/Libraries/LibWeb/DOM/DOMImplementation.cpp
@@ -56,7 +56,7 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> DOMImplementation::create_docume
 
     // 3. If qualifiedName is not the empty string, then set element to the result of running the internal createElementNS steps, given document, namespace, qualifiedName, and an empty dictionary.
     if (!qualified_name.is_empty())
-        element = TRY(xml_document->create_element_ns(namespace_.value().to_deprecated_string(), qualified_name.to_deprecated_string(), ElementCreationOptions {}));
+        element = TRY(xml_document->create_element_ns(namespace_.value(), qualified_name, ElementCreationOptions {}));
 
     // 4. If doctype is non-null, append doctype to document.
     if (doctype)
@@ -74,13 +74,13 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> DOMImplementation::create_docume
 
     if (deprecated_namespace == Namespace::HTML) {
         // -> HTML namespace
-        xml_document->set_content_type("application/xhtml+xml");
+        xml_document->set_content_type("application/xhtml+xml"_string);
     } else if (deprecated_namespace == Namespace::SVG) {
         // -> SVG namespace
-        xml_document->set_content_type("image/svg+xml");
+        xml_document->set_content_type("image/svg+xml"_string);
     } else {
         // -> Any other namespace
-        xml_document->set_content_type("application/xml");
+        xml_document->set_content_type("application/xml"_string);
     }
 
     // 8. Return document.
@@ -94,7 +94,7 @@ JS::NonnullGCPtr<Document> DOMImplementation::create_html_document(Optional<Stri
     auto html_document = Document::create(realm());
 
     // 2. Set doc’s content type to "text/html".
-    html_document->set_content_type("text/html");
+    html_document->set_content_type("text/html"_string);
 
     html_document->set_ready_for_post_load_tasks(true);
 
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index 2e84456cf5..14dfc31fd4 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -257,7 +257,7 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> Document::create_and_initialize(
     //    and navigation id is navigationParams's id.
     auto document = HTML::HTMLDocument::create(window->realm());
     document->m_type = type;
-    document->m_content_type = move(content_type);
+    document->m_content_type = MUST(String::from_deprecated_string(content_type));
     document->set_origin(navigation_params.origin);
     document->m_policy_container = navigation_params.policy_container;
     document->m_active_sandboxing_flag_set = navigation_params.final_sandboxing_flag_set;
@@ -410,7 +410,7 @@ JS::GCPtr<Selection::Selection> Document::get_selection() const
 }
 
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-document-write
-WebIDL::ExceptionOr<void> Document::write(Vector<DeprecatedString> const& strings)
+WebIDL::ExceptionOr<void> Document::write(Vector<String> const& strings)
 {
     StringBuilder builder;
     builder.join(""sv, strings);
@@ -419,7 +419,7 @@ WebIDL::ExceptionOr<void> Document::write(Vector<DeprecatedString> const& string
 }
 
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-document-writeln
-WebIDL::ExceptionOr<void> Document::writeln(Vector<DeprecatedString> const& strings)
+WebIDL::ExceptionOr<void> Document::writeln(Vector<String> const& strings)
 {
     StringBuilder builder;
     builder.join(""sv, strings);
@@ -464,7 +464,7 @@ WebIDL::ExceptionOr<void> Document::run_the_document_write_steps(StringView inpu
 }
 
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-document-open
-WebIDL::ExceptionOr<Document*> Document::open(StringView, StringView)
+WebIDL::ExceptionOr<Document*> Document::open(Optional<String> const&, Optional<String> const&)
 {
     // 1. If document is an XML document, then throw an "InvalidStateError" DOMException exception.
     if (m_type == Type::XML)
@@ -720,7 +720,7 @@ DeprecatedString Document::title() const
 }
 
 // https://html.spec.whatwg.org/multipage/dom.html#document.title
-WebIDL::ExceptionOr<void> Document::set_title(DeprecatedString const& title)
+WebIDL::ExceptionOr<void> Document::set_title(String const& title)
 {
     auto* document_element = this->document_element();
 
@@ -744,7 +744,7 @@ WebIDL::ExceptionOr<void> Document::set_title(DeprecatedString const& title)
         }
 
         // 3. String replace all with the given value within element.
-        element->string_replace_all(title);
+        element->string_replace_all(title.to_deprecated_string());
     }
 
     // -> If the document element is in the HTML namespace
@@ -773,7 +773,7 @@ WebIDL::ExceptionOr<void> Document::set_title(DeprecatedString const& title)
         }
 
         // 4. String replace all with the given value within element.
-        element->string_replace_all(title);
+        element->string_replace_all(title.to_deprecated_string());
     }
 
     // -> Otherwise
@@ -784,7 +784,7 @@ WebIDL::ExceptionOr<void> Document::set_title(DeprecatedString const& title)
 
     if (auto* page = this->page()) {
         if (browsing_context() == &page->top_level_browsing_context())
-            page->client().page_did_change_title(title);
+            page->client().page_did_change_title(title.to_deprecated_string());
     }
 
     return {};
@@ -1182,10 +1182,11 @@ void Document::set_hovered_node(Node* node)
     }
 }
 
-JS::NonnullGCPtr<HTMLCollection> Document::get_elements_by_name(DeprecatedString const& name)
+JS::NonnullGCPtr<HTMLCollection> Document::get_elements_by_name(String const& name)
 {
-    return HTMLCollection::create(*this, HTMLCollection::Scope::Descendants, [name](Element const& element) {
-        return element.name() == name;
+    auto deprecated_name = name.to_deprecated_string();
+    return HTMLCollection::create(*this, HTMLCollection::Scope::Descendants, [deprecated_name](Element const& element) {
+        return element.name() == deprecated_name;
     });
 }
 
@@ -1359,14 +1360,12 @@ void Document::evaluate_javascript_url(StringView url)
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createelement
-WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element(DeprecatedString const& a_local_name, Variant<DeprecatedString, ElementCreationOptions> const& options)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element(String const& a_local_name, Variant<String, ElementCreationOptions> const& options)
 {
-    auto& vm = this->vm();
-
-    auto local_name = a_local_name;
+    auto local_name = a_local_name.to_deprecated_string();
 
     // 1. If localName does not match the Name production, then throw an "InvalidCharacterError" DOMException.
-    if (!is_valid_name(local_name))
+    if (!is_valid_name(a_local_name))
         return WebIDL::InvalidCharacterError::create(realm(), "Invalid character in tag name."_fly_string);
 
     // 2. If this is an HTML document, then set localName to localName in ASCII lowercase.
@@ -1379,8 +1378,8 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element(Deprecat
     // 4. If options is a dictionary and options["is"] exists, then set is to it.
     if (options.has<ElementCreationOptions>()) {
         auto const& element_creation_options = options.get<ElementCreationOptions>();
-        if (!element_creation_options.is.is_null())
-            is_value = TRY_OR_THROW_OOM(vm, String::from_deprecated_string(element_creation_options.is));
+        if (element_creation_options.is.has_value())
+            is_value = element_creation_options.is.value();
     }
 
     // 5. Let namespace be the HTML namespace, if this is an HTML document or this’s content type is "application/xhtml+xml"; otherwise null.
@@ -1394,12 +1393,15 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element(Deprecat
 
 // https://dom.spec.whatwg.org/#dom-document-createelementns
 // https://dom.spec.whatwg.org/#internal-createelementns-steps
-WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element_ns(DeprecatedString const& namespace_, DeprecatedString const& qualified_name, Variant<DeprecatedString, ElementCreationOptions> const& options)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element_ns(Optional<String> const& namespace_, String const& qualified_name, Variant<String, ElementCreationOptions> const& options)
 {
-    auto& vm = this->vm();
+    // FIXME: This conversion is ugly
+    StringView namespace_view;
+    if (namespace_.has_value())
+        namespace_view = namespace_->bytes_as_string_view();
 
     // 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(realm(), namespace_, qualified_name));
+    auto extracted_qualified_name = TRY(validate_and_extract(realm(), namespace_view, qualified_name.to_deprecated_string()));
 
     // 2. Let is be null.
     Optional<String> is_value;
@@ -1407,8 +1409,8 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> Document::create_element_ns(Depre
     // 3. If options is a dictionary and options["is"] exists, then set is to it.
     if (options.has<ElementCreationOptions>()) {
         auto const& element_creation_options = options.get<ElementCreationOptions>();
-        if (!element_creation_options.is.is_null())
-            is_value = TRY_OR_THROW_OOM(vm, String::from_deprecated_string(element_creation_options.is));
+        if (element_creation_options.is.has_value())
+            is_value = element_creation_options.is.value();
     }
 
     // 4. Return the result of creating an element given document, localName, namespace, prefix, is, and with the synchronous custom elements flag set.
@@ -1420,25 +1422,25 @@ JS::NonnullGCPtr<DocumentFragment> Document::create_document_fragment()
     return heap().allocate<DocumentFragment>(realm(), *this);
 }
 
-JS::NonnullGCPtr<Text> Document::create_text_node(DeprecatedString const& data)
+JS::NonnullGCPtr<Text> Document::create_text_node(String const& data)
 {
-    return heap().allocate<Text>(realm(), *this, MUST(String::from_deprecated_string(data)));
+    return heap().allocate<Text>(realm(), *this, data);
 }
 
-JS::NonnullGCPtr<Comment> Document::create_comment(DeprecatedString const& data)
+JS::NonnullGCPtr<Comment> Document::create_comment(String const& data)
 {
-    return heap().allocate<Comment>(realm(), *this, MUST(String::from_deprecated_string(data)));
+    return heap().allocate<Comment>(realm(), *this, data);
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createprocessinginstruction
-WebIDL::ExceptionOr<JS::NonnullGCPtr<ProcessingInstruction>> Document::create_processing_instruction(DeprecatedString const& target, DeprecatedString const& data)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<ProcessingInstruction>> Document::create_processing_instruction(String const& target, String const& data)
 {
     // FIXME: 1. If target does not match the Name production, then throw an "InvalidCharacterError" DOMException.
 
     // FIXME: 2. If data contains the string "?>", then throw an "InvalidCharacterError" DOMException.
 
     // 3. Return a new ProcessingInstruction node, with target set to target, data set to data, and node document set to this.
-    return heap().allocate<ProcessingInstruction>(realm(), *this, data, target);
+    return heap().allocate<ProcessingInstruction>(realm(), *this, data.to_deprecated_string(), target.to_deprecated_string());
 }
 
 JS::NonnullGCPtr<Range> Document::create_range()
@@ -1447,7 +1449,7 @@ JS::NonnullGCPtr<Range> Document::create_range()
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createevent
-WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> Document::create_event(DeprecatedString const& interface)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> Document::create_event(StringView interface)
 {
     auto& realm = this->realm();
 
@@ -2242,7 +2244,7 @@ static inline bool is_valid_name_character(u32 code_point)
         || (code_point >= 0x203f && code_point <= 0x2040);
 }
 
-bool Document::is_valid_name(DeprecatedString const& name)
+bool Document::is_valid_name(String const& name)
 {
     auto code_points = Utf8View { name };
     auto it = code_points.begin();
@@ -2491,7 +2493,7 @@ DeprecatedString Document::domain() const
     return URLParser::serialize_host(effective_domain.release_value()).release_value_but_fixme_should_propagate_errors().to_deprecated_string();
 }
 
-void Document::set_domain(DeprecatedString const& domain)
+void Document::set_domain(String const& domain)
 {
     dbgln("(STUBBED) Document::set_domain(domain='{}')", domain);
 }
@@ -2919,7 +2921,7 @@ void Document::did_stop_being_active_document_in_browsing_context(Badge<HTML::Br
 }
 
 // https://w3c.github.io/editing/docs/execCommand/#querycommandsupported()
-bool Document::query_command_supported(DeprecatedString const& command) const
+bool Document::query_command_supported(String const& command) const
 {
     dbgln("(STUBBED) Document::query_command_supported(command='{}')", command);
     return false;
@@ -2981,7 +2983,7 @@ DeprecatedString Document::dump_accessibility_tree_as_json()
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createattribute
-WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> Document::create_attribute(DeprecatedString const& local_name)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> Document::create_attribute(String const& local_name)
 {
     // 1. If localName does not match the Name production in XML, then throw an "InvalidCharacterError" DOMException.
     if (!is_valid_name(local_name))
@@ -2989,14 +2991,20 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> Document::create_attribute(Deprecate
 
     // 2. If this is an HTML document, then set localName to localName in ASCII lowercase.
     // 3. Return a new attribute whose local name is localName and node document is this.
-    return Attr::create(*this, is_html_document() ? local_name.to_lowercase() : local_name);
+    auto deprecated_local_name = local_name.to_deprecated_string();
+    return Attr::create(*this, is_html_document() ? deprecated_local_name.to_lowercase() : deprecated_local_name);
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createattributens
-WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> Document::create_attribute_ns(DeprecatedString const& namespace_, DeprecatedString const& qualified_name)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> Document::create_attribute_ns(Optional<String> const& namespace_, String const& qualified_name)
 {
+    // FIXME: This conversion is ugly
+    StringView namespace_view;
+    if (namespace_.has_value())
+        namespace_view = namespace_->bytes_as_string_view();
+
     // 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(realm(), namespace_, qualified_name));
+    auto extracted_qualified_name = TRY(validate_and_extract(realm(), namespace_view, qualified_name.to_deprecated_string()));
 
     // 2. Return a new attribute whose namespace is namespace, namespace prefix is prefix, local name is localName, and node document is this.
 
diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index fe3d68be5c..587f0144d6 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -70,7 +70,7 @@ struct DocumentUnloadTimingInfo {
 };
 
 struct ElementCreationOptions {
-    DeprecatedString is;
+    Optional<String> is;
 };
 
 enum class PolicyControlledFeature {
@@ -173,7 +173,7 @@ public:
     WebIDL::ExceptionOr<void> set_body(HTML::HTMLElement* new_body);
 
     DeprecatedString title() const;
-    WebIDL::ExceptionOr<void> set_title(DeprecatedString const&);
+    WebIDL::ExceptionOr<void> set_title(String const&);
 
     HTML::BrowsingContext* browsing_context() { return m_browsing_context.ptr(); }
     HTML::BrowsingContext const* browsing_context() const { return m_browsing_context.ptr(); }
@@ -216,7 +216,7 @@ public:
     void schedule_style_update();
     void schedule_layout_update();
 
-    JS::NonnullGCPtr<HTMLCollection> get_elements_by_name(DeprecatedString const&);
+    JS::NonnullGCPtr<HTMLCollection> get_elements_by_name(String const&);
     JS::NonnullGCPtr<HTMLCollection> get_elements_by_class_name(StringView);
 
     JS::NonnullGCPtr<HTMLCollection> applets();
@@ -237,17 +237,17 @@ public:
     void navigate_to_javascript_url(StringView url);
     void evaluate_javascript_url(StringView url);
 
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element(DeprecatedString const& local_name, Variant<DeprecatedString, ElementCreationOptions> const& options);
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element_ns(DeprecatedString const& namespace_, DeprecatedString const& qualified_name, Variant<DeprecatedString, ElementCreationOptions> const& options);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element(String const& local_name, Variant<String, ElementCreationOptions> const& options);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Element>> create_element_ns(Optional<String> const& namespace_, String const& qualified_name, Variant<String, ElementCreationOptions> const& options);
     JS::NonnullGCPtr<DocumentFragment> create_document_fragment();
-    JS::NonnullGCPtr<Text> create_text_node(DeprecatedString const& data);
-    JS::NonnullGCPtr<Comment> create_comment(DeprecatedString const& data);
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<ProcessingInstruction>> create_processing_instruction(DeprecatedString const& target, DeprecatedString const& data);
+    JS::NonnullGCPtr<Text> create_text_node(String const& data);
+    JS::NonnullGCPtr<Comment> create_comment(String const& data);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<ProcessingInstruction>> create_processing_instruction(String const& target, String const& data);
 
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> create_attribute(DeprecatedString const& local_name);
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> create_attribute_ns(DeprecatedString const& namespace_, DeprecatedString const& qualified_name);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> create_attribute(String const& local_name);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Attr>> create_attribute_ns(Optional<String> const& namespace_, String const& qualified_name);
 
-    WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> create_event(DeprecatedString const& interface);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> create_event(StringView interface);
     JS::NonnullGCPtr<Range> create_range();
 
     void set_pending_parsing_blocking_script(Badge<HTML::HTMLScriptElement>, HTML::HTMLScriptElement*);
@@ -316,28 +316,28 @@ public:
 
     void set_window(HTML::Window&);
 
-    WebIDL::ExceptionOr<void> write(Vector<DeprecatedString> const& strings);
-    WebIDL::ExceptionOr<void> writeln(Vector<DeprecatedString> const& strings);
+    WebIDL::ExceptionOr<void> write(Vector<String> const& strings);
+    WebIDL::ExceptionOr<void> writeln(Vector<String> const& strings);
 
-    WebIDL::ExceptionOr<Document*> open(StringView = ""sv, StringView = ""sv);
+    WebIDL::ExceptionOr<Document*> open(Optional<String> const& = {}, Optional<String> const& = {});
     WebIDL::ExceptionOr<JS::GCPtr<HTML::WindowProxy>> open(StringView url, StringView name, StringView features);
     WebIDL::ExceptionOr<void> close();
 
     HTML::Window* default_view() { return m_window.ptr(); }
     HTML::Window const* default_view() const { return m_window.ptr(); }
 
-    DeprecatedString const& content_type() const { return m_content_type; }
-    void set_content_type(DeprecatedString const& content_type) { m_content_type = content_type; }
+    String const& content_type() const { return m_content_type; }
+    void set_content_type(String content_type) { m_content_type = move(content_type); }
 
     bool has_encoding() const { return m_encoding.has_value(); }
-    Optional<DeprecatedString> const& encoding() const { return m_encoding; }
-    DeprecatedString encoding_or_default() const { return m_encoding.value_or("UTF-8"); }
-    void set_encoding(Optional<DeprecatedString> const& encoding) { m_encoding = encoding; }
+    Optional<String> const& encoding() const { return m_encoding; }
+    String encoding_or_default() const { return m_encoding.value_or("UTF-8"_string); }
+    void set_encoding(Optional<String> encoding) { m_encoding = move(encoding); }
 
     // NOTE: These are intended for the JS bindings
-    DeprecatedString character_set() const { return encoding_or_default(); }
-    DeprecatedString charset() const { return encoding_or_default(); }
-    DeprecatedString input_encoding() const { return encoding_or_default(); }
+    String character_set() const { return encoding_or_default(); }
+    String charset() const { return encoding_or_default(); }
+    String input_encoding() const { return encoding_or_default(); }
 
     bool ready_for_post_load_tasks() const { return m_ready_for_post_load_tasks; }
     void set_ready_for_post_load_tasks(bool ready) { m_ready_for_post_load_tasks = ready; }
@@ -409,7 +409,7 @@ public:
     void set_is_temporary_document_for_fragment_parsing(Badge<HTML::HTMLParser>) { m_temporary_document_for_fragment_parsing = true; }
     [[nodiscard]] bool is_temporary_document_for_fragment_parsing() const { return m_temporary_document_for_fragment_parsing; }
 
-    static bool is_valid_name(DeprecatedString const&);
+    static bool is_valid_name(String const&);
 
     struct PrefixAndTagName {
         DeprecatedFlyString prefix;
@@ -449,7 +449,7 @@ public:
     void set_is_initial_about_blank(bool b) { m_is_initial_about_blank = b; }
 
     DeprecatedString domain() const;
-    void set_domain(DeprecatedString const& domain);
+    void set_domain(String const&);
 
     auto& pending_scroll_event_targets() { return m_pending_scroll_event_targets; }
     auto& pending_scrollend_event_targets() { return m_pending_scrollend_event_targets; }
@@ -504,7 +504,7 @@ public:
 
     void did_stop_being_active_document_in_browsing_context(Badge<HTML::BrowsingContext>);
 
-    bool query_command_supported(DeprecatedString const&) const;
+    bool query_command_supported(String const&) const;
 
     DeprecatedString dump_accessibility_tree_as_json();
 
@@ -604,8 +604,8 @@ private:
     JS::GCPtr<Document> m_appropriate_template_contents_owner_document;
 
     HTML::DocumentReadyState m_readiness { HTML::DocumentReadyState::Loading };
-    DeprecatedString m_content_type { "application/xml" };
-    Optional<DeprecatedString> m_encoding;
+    String m_content_type { "application/xml"_string };
+    Optional<String> m_encoding;
 
     bool m_ready_for_post_load_tasks { false };
 
diff --git a/Userland/Libraries/LibWeb/DOM/Document.idl b/Userland/Libraries/LibWeb/DOM/Document.idl
index becfc025cc..a2d285b1c4 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.idl
+++ b/Userland/Libraries/LibWeb/DOM/Document.idl
@@ -23,7 +23,7 @@
 #import <Selection/Selection.idl>
 
 // https://dom.spec.whatwg.org/#document
-[Exposed=Window, UseDeprecatedAKString]
+[Exposed=Window]
 interface Document : Node {
     constructor();
 
diff --git a/Userland/Libraries/LibWeb/DOM/DocumentLoading.cpp b/Userland/Libraries/LibWeb/DOM/DocumentLoading.cpp
index 30dae81445..6c65b004de 100644
--- a/Userland/Libraries/LibWeb/DOM/DocumentLoading.cpp
+++ b/Userland/Libraries/LibWeb/DOM/DocumentLoading.cpp
@@ -87,7 +87,7 @@ static bool build_text_document(DOM::Document& document, ByteBuffer const& data)
     auto title_element = DOM::create_element(document, HTML::TagNames::title, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
     MUST(head_element->append_child(title_element));
 
-    auto title_text = document.create_text_node(document.url().basename());
+    auto title_text = document.create_text_node(MUST(String::from_deprecated_string(document.url().basename())));
     MUST(title_element->append_child(title_text));
 
     auto body_element = DOM::create_element(document, HTML::TagNames::body, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
@@ -96,7 +96,7 @@ static bool build_text_document(DOM::Document& document, ByteBuffer const& data)
     auto pre_element = DOM::create_element(document, HTML::TagNames::pre, Namespace::HTML).release_value_but_fixme_should_propagate_errors();
     MUST(body_element->append_child(pre_element));
 
-    MUST(pre_element->append_child(document.create_text_node(DeprecatedString::copy(data))));
+    MUST(pre_element->append_child(document.create_text_node(String::from_utf8(StringView { data }).release_value_but_fixme_should_propagate_errors())));
     return true;
 }
 
@@ -206,13 +206,13 @@ bool parse_document(DOM::Document& document, ByteBuffer const& data)
         parser->run(document.url());
         return true;
     }
-    if (mime_type.ends_with("+xml"sv) || mime_type.is_one_of("text/xml", "application/xml"))
+    if (mime_type.ends_with_bytes("+xml"sv) || mime_type.is_one_of("text/xml", "application/xml"))
         return build_xml_document(document, data);
-    if (mime_type.starts_with("image/"sv))
+    if (mime_type.starts_with_bytes("image/"sv))
         return build_image_document(document, data);
-    if (mime_type.starts_with("video/"sv))
+    if (mime_type.starts_with_bytes("video/"sv))
         return build_video_document(document);
-    if (mime_type.starts_with("audio/"sv))
+    if (mime_type.starts_with_bytes("audio/"sv))
         return build_audio_document(document);
     if (mime_type == "text/plain" || mime_type == "application/json")
         return build_text_document(document, data);
@@ -236,8 +236,8 @@ JS::GCPtr<DOM::Document> load_document(Optional<HTML::NavigationParams> navigati
     if (navigation_params->response->body()) {
         auto process_body = [navigation_params, document](ByteBuffer bytes) {
             auto extracted_mime_type = navigation_params->response->header_list()->extract_mime_type().release_value_but_fixme_should_propagate_errors();
-            auto mime_type = extracted_mime_type.has_value() ? extracted_mime_type.value().essence().bytes_as_string_view() : StringView {};
-            document->set_content_type(mime_type);
+            auto mime_type = extracted_mime_type.has_value() ? extracted_mime_type.value().essence() : String {};
+            document->set_content_type(move(mime_type));
 
             if (!parse_document(*document, bytes)) {
                 // FIXME: Load html page with an error if parsing failed.
diff --git a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
index 43876867f6..0054282e72 100644
--- a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
+++ b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
@@ -210,7 +210,7 @@ JS::NonnullGCPtr<BrowsingContext> BrowsingContext::create_a_new_browsing_context
     window->set_associated_document(*document);
 
     document->set_quirks_mode(DOM::QuirksMode::Yes);
-    document->set_content_type("text/html");
+    document->set_content_type("text/html"_string);
     document->set_origin(origin);
     document->set_url(AK::URL("about:blank"));
     document->set_cross_origin_opener_policy(coop);
@@ -370,7 +370,7 @@ WebIDL::ExceptionOr<BrowsingContext::BrowsingContextAndDocument> BrowsingContext
     document->set_document_type(DOM::Document::Type::HTML);
 
     // content type: "text/html"
-    document->set_content_type("text/html");
+    document->set_content_type("text/html"_string);
 
     // mode: "quirks"
     document->set_quirks_mode(DOM::QuirksMode::Yes);
@@ -626,7 +626,7 @@ void BrowsingContext::scroll_to_anchor(DeprecatedString const& fragment)
 
     auto element = document->get_element_by_id(fragment);
     if (!element) {
-        auto candidates = document->get_elements_by_name(fragment);
+        auto candidates = document->get_elements_by_name(MUST(String::from_deprecated_string(fragment)));
         for (auto& candidate : candidates->collect_matching_elements()) {
             if (is<HTML::HTMLAnchorElement>(*candidate)) {
                 element = &verify_cast<HTML::HTMLAnchorElement>(*candidate);
diff --git a/Userland/Libraries/LibWeb/HTML/DOMParser.cpp b/Userland/Libraries/LibWeb/HTML/DOMParser.cpp
index 0ef54dd61c..a75754c8c5 100644
--- a/Userland/Libraries/LibWeb/HTML/DOMParser.cpp
+++ b/Userland/Libraries/LibWeb/HTML/DOMParser.cpp
@@ -43,7 +43,7 @@ JS::NonnullGCPtr<DOM::Document> DOMParser::parse_from_string(StringView string,
         // -> "text/html"
         // 1. Set document's type to "html".
         document = HTML::HTMLDocument::create(realm(), verify_cast<HTML::Window>(relevant_global_object(*this)).associated_document().url());
-        document->set_content_type(Bindings::idl_enum_to_string(type).to_deprecated_string());
+        document->set_content_type(Bindings::idl_enum_to_string(type));
         document->set_document_type(DOM::Document::Type::HTML);
 
         // 2. Create an HTML parser parser, associated with document.
@@ -57,7 +57,7 @@ JS::NonnullGCPtr<DOM::Document> DOMParser::parse_from_string(StringView string,
     } else {
         // -> Otherwise
         document = DOM::Document::create(realm(), verify_cast<HTML::Window>(relevant_global_object(*this)).associated_document().url());
-        document->set_content_type(Bindings::idl_enum_to_string(type).to_deprecated_string());
+        document->set_content_type(Bindings::idl_enum_to_string(type));
 
         // 1. Create an XML parser parse, associated with document, and with XML scripting support disabled.
         XML::Parser parser(string, { .resolve_external_resource = resolve_xml_resource });
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
index 53c65a38e4..e0b8ae366a 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
@@ -125,7 +125,7 @@ WebIDL::ExceptionOr<void> HTMLElement::set_content_editable(StringView content_e
 void HTMLElement::set_inner_text(StringView text)
 {
     remove_all_children();
-    MUST(append_child(document().create_text_node(text)));
+    MUST(append_child(document().create_text_node(MUST(String::from_utf8(text)))));
 
     set_needs_style_update(true);
 }
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
index 10d0b4d052..489d25ab85 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
@@ -346,7 +346,7 @@ void HTMLLinkElement::process_stylesheet_resource(bool success, Fetch::Infrastru
         if (auto charset = deprecated_attribute(HTML::AttributeNames::charset); !charset.is_null())
             encoding = charset;
         else
-            encoding = document().encoding_or_default();
+            encoding = document().encoding_or_default().to_deprecated_string();
 
         auto decoder = TextCodec::decoder_for(encoding);
 
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLScriptElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLScriptElement.cpp
index 817adda7b7..0c7d99bd9d 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLScriptElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLScriptElement.cpp
@@ -290,8 +290,7 @@ void HTMLScriptElement::prepare_script()
     }
 
     if (!encoding.has_value()) {
-        auto document_encoding = document().encoding_or_default();
-        encoding = String::from_deprecated_string(document_encoding).release_value_but_fixme_should_propagate_errors();
+        encoding = document().encoding_or_default();
     }
 
     VERIFY(encoding.has_value());
diff --git a/Userland/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp b/Userland/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp
index 70fc9b000d..45308401ba 100644
--- a/Userland/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp
@@ -136,7 +136,7 @@ HTMLParser::HTMLParser(DOM::Document& document, StringView input, DeprecatedStri
     m_document->set_parser({}, *this);
     auto standardized_encoding = TextCodec::get_standardized_encoding(encoding);
     VERIFY(standardized_encoding.has_value());
-    m_document->set_encoding(standardized_encoding.value());
+    m_document->set_encoding(MUST(String::from_utf8(standardized_encoding.value())));
 }
 
 HTMLParser::HTMLParser(DOM::Document& document)
@@ -3774,7 +3774,7 @@ JS::NonnullGCPtr<HTMLParser> HTMLParser::create_for_scripting(DOM::Document& doc
 JS::NonnullGCPtr<HTMLParser> HTMLParser::create_with_uncertain_encoding(DOM::Document& document, ByteBuffer const& input)
 {
     if (document.has_encoding())
-        return document.heap().allocate_without_realm<HTMLParser>(document, input, document.encoding().value());
+        return document.heap().allocate_without_realm<HTMLParser>(document, input, document.encoding().value().to_deprecated_string());
     auto encoding = run_encoding_sniffing_algorithm(document, input);
     dbgln_if(HTML_PARSER_DEBUG, "The encoding sniffing algorithm returned encoding '{}'", encoding);
     return document.heap().allocate_without_realm<HTMLParser>(document, input, encoding);
diff --git a/Userland/Libraries/LibWeb/HTML/Scripting/WindowEnvironmentSettingsObject.cpp b/Userland/Libraries/LibWeb/HTML/Scripting/WindowEnvironmentSettingsObject.cpp
index 0fe78ec19e..64b6d8dcfa 100644
--- a/Userland/Libraries/LibWeb/HTML/Scripting/WindowEnvironmentSettingsObject.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Scripting/WindowEnvironmentSettingsObject.cpp
@@ -91,7 +91,7 @@ JS::GCPtr<DOM::Document> WindowEnvironmentSettingsObject::responsible_document()
 DeprecatedString WindowEnvironmentSettingsObject::api_url_character_encoding()
 {
     // Return the current character encoding of window's associated Document.
-    return m_window->associated_document().encoding_or_default();
+    return m_window->associated_document().encoding_or_default().to_deprecated_string();
 }
 
 // https://html.spec.whatwg.org/multipage/window-object.html#script-settings-for-window-objects:api-base-url
diff --git a/Userland/Libraries/LibWeb/Loader/FrameLoader.cpp b/Userland/Libraries/LibWeb/Loader/FrameLoader.cpp
index 576cad8f2a..ad1a74618a 100644
--- a/Userland/Libraries/LibWeb/Loader/FrameLoader.cpp
+++ b/Userland/Libraries/LibWeb/Loader/FrameLoader.cpp
@@ -326,8 +326,13 @@ void FrameLoader::resource_did_load()
     };
     auto document = DOM::Document::create_and_initialize(DOM::Document::Type::HTML, "text/html", move(navigation_params)).release_value_but_fixme_should_propagate_errors();
     document->set_url(url);
-    document->set_encoding(resource()->encoding());
-    document->set_content_type(resource()->mime_type());
+
+    if (resource()->encoding().has_value())
+        document->set_encoding(MUST(String::from_deprecated_string(resource()->encoding().value())));
+    else
+        document->set_encoding({});
+
+    document->set_content_type(MUST(String::from_deprecated_string(resource()->mime_type())));
 
     browsing_context().set_active_document(document);
     if (auto* page = browsing_context().page())
diff --git a/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp b/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
index 257fa19900..75149cb73b 100644
--- a/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
+++ b/Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
@@ -324,10 +324,10 @@ void XMLHttpRequest::set_document_response()
         charset = "UTF-8"sv;
 
     // 8. Set document’s encoding to charset.
-    document->set_encoding(charset->to_deprecated_string());
+    document->set_encoding(MUST(String::from_utf8(charset.value())));
 
     // 9. Set document’s content type to finalMIME.
-    document->set_content_type(MUST(final_mine.serialized()).to_deprecated_string());
+    document->set_content_type(MUST(final_mine.serialized()));
 
     // 10. Set document’s URL to xhr’s response’s URL.
     document->set_url(m_response->url().value_or({}));
diff --git a/Userland/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp b/Userland/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp
index 18ac9d3d5d..76a5fd4c9d 100644
--- a/Userland/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp
+++ b/Userland/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp
@@ -146,7 +146,7 @@ void XMLDocumentBuilder::text(StringView data)
         auto string = DeprecatedString::empty();
         if (!data.is_null())
             string = data.to_deprecated_string();
-        auto node = m_document->create_text_node(string);
+        auto node = m_document->create_text_node(MUST(String::from_deprecated_string(string)));
         MUST(m_current_node->append_child(node));
     }
 }
@@ -158,7 +158,7 @@ void XMLDocumentBuilder::comment(StringView data)
     auto string = DeprecatedString::empty();
     if (!data.is_null())
         string = data.to_deprecated_string();
-    MUST(m_document->append_child(m_document->create_comment(string)));
+    MUST(m_document->append_child(m_document->create_comment(MUST(String::from_deprecated_string(string)))));
 }
 
 void XMLDocumentBuilder::document_end()