diff --git a/Userland/Libraries/LibWeb/CSS/CSSSupportsRule.cpp b/Userland/Libraries/LibWeb/CSS/CSSSupportsRule.cpp
index 7289a0ae30..54acba5ff4 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSSupportsRule.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSSupportsRule.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -32,7 +32,7 @@ JS::ThrowCompletionOr<void> CSSSupportsRule::initialize(JS::Realm& realm)
 
 DeprecatedString CSSSupportsRule::condition_text() const
 {
-    return m_supports->to_deprecated_string();
+    return m_supports->to_string().release_value_but_fixme_should_propagate_errors().to_deprecated_string();
 }
 
 void CSSSupportsRule::set_condition_text(DeprecatedString text)
diff --git a/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp b/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
index d3f852cfa8..9e43248edf 100644
--- a/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
@@ -1395,7 +1395,7 @@ Optional<Supports::Feature> Parser::parse_supports_feature(TokenStream<Component
         if (auto declaration = consume_a_declaration(block_tokens); declaration.has_value()) {
             transaction.commit();
             return Supports::Feature {
-                Supports::Declaration { declaration->to_string().release_value_but_fixme_should_propagate_errors().to_deprecated_string() }
+                Supports::Declaration { declaration->to_string().release_value_but_fixme_should_propagate_errors() }
             };
         }
     }
@@ -1408,7 +1408,7 @@ Optional<Supports::Feature> Parser::parse_supports_feature(TokenStream<Component
             builder.append(item.to_string().release_value_but_fixme_should_propagate_errors());
         transaction.commit();
         return Supports::Feature {
-            Supports::Selector { builder.to_deprecated_string() }
+            Supports::Selector { builder.to_string().release_value_but_fixme_should_propagate_errors() }
         };
     }
 
diff --git a/Userland/Libraries/LibWeb/CSS/Supports.cpp b/Userland/Libraries/LibWeb/CSS/Supports.cpp
index 41287f0b8c..fff9c5d372 100644
--- a/Userland/Libraries/LibWeb/CSS/Supports.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Supports.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2022, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -73,45 +73,45 @@ bool Supports::Feature::evaluate() const
         });
 }
 
-DeprecatedString Supports::Declaration::to_deprecated_string() const
+ErrorOr<String> Supports::Declaration::to_string() const
 {
-    return DeprecatedString::formatted("({})", declaration);
+    return String::formatted("({})", declaration);
 }
 
-DeprecatedString Supports::Selector::to_deprecated_string() const
+ErrorOr<String> Supports::Selector::to_string() const
 {
-    return DeprecatedString::formatted("selector({})", selector);
+    return String::formatted("selector({})", selector);
 }
 
-DeprecatedString Supports::Feature::to_deprecated_string() const
+ErrorOr<String> Supports::Feature::to_string() const
 {
-    return value.visit([](auto& it) { return it.to_deprecated_string(); });
+    return value.visit([](auto& it) { return it.to_string(); });
 }
 
-DeprecatedString Supports::InParens::to_deprecated_string() const
+ErrorOr<String> Supports::InParens::to_string() const
 {
     return value.visit(
-        [](NonnullOwnPtr<Condition> const& condition) -> DeprecatedString { return DeprecatedString::formatted("({})", condition->to_deprecated_string()); },
-        [](Supports::Feature const& it) -> DeprecatedString { return it.to_deprecated_string(); },
-        [](GeneralEnclosed const& it) -> DeprecatedString { return it.to_string(); });
+        [](NonnullOwnPtr<Condition> const& condition) -> ErrorOr<String> { return String::formatted("({})", TRY(condition->to_string())); },
+        [](Supports::Feature const& it) -> ErrorOr<String> { return it.to_string(); },
+        [](GeneralEnclosed const& it) -> ErrorOr<String> { return String::from_utf8(it.to_string()); });
 }
 
-DeprecatedString Supports::Condition::to_deprecated_string() const
+ErrorOr<String> Supports::Condition::to_string() const
 {
     switch (type) {
     case Type::Not:
-        return DeprecatedString::formatted("not {}", children.first().to_deprecated_string());
+        return String::formatted("not {}", TRY(children.first().to_string()));
     case Type::And:
-        return DeprecatedString::join(" and "sv, children);
+        return String::join(" and "sv, children);
     case Type::Or:
-        return DeprecatedString::join(" or "sv, children);
+        return String::join(" or "sv, children);
     }
     VERIFY_NOT_REACHED();
 }
 
-DeprecatedString Supports::to_deprecated_string() const
+ErrorOr<String> Supports::to_string() const
 {
-    return m_condition->to_deprecated_string();
+    return m_condition->to_string();
 }
 
 }
diff --git a/Userland/Libraries/LibWeb/CSS/Supports.h b/Userland/Libraries/LibWeb/CSS/Supports.h
index 385fc5eb7f..99f8f01afc 100644
--- a/Userland/Libraries/LibWeb/CSS/Supports.h
+++ b/Userland/Libraries/LibWeb/CSS/Supports.h
@@ -1,14 +1,14 @@
 /*
- * Copyright (c) 2021-2022, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #pragma once
 
-#include <AK/DeprecatedString.h>
 #include <AK/NonnullOwnPtr.h>
 #include <AK/RefCounted.h>
+#include <AK/String.h>
 #include <AK/Variant.h>
 #include <AK/Vector.h>
 #include <LibWeb/CSS/GeneralEnclosed.h>
@@ -22,21 +22,21 @@ class Supports final : public RefCounted<Supports> {
 
 public:
     struct Declaration {
-        DeprecatedString declaration;
+        String declaration;
         bool evaluate() const;
-        DeprecatedString to_deprecated_string() const;
+        ErrorOr<String> to_string() const;
     };
 
     struct Selector {
-        DeprecatedString selector;
+        String selector;
         bool evaluate() const;
-        DeprecatedString to_deprecated_string() const;
+        ErrorOr<String> to_string() const;
     };
 
     struct Feature {
         Variant<Declaration, Selector> value;
         bool evaluate() const;
-        DeprecatedString to_deprecated_string() const;
+        ErrorOr<String> to_string() const;
     };
 
     struct Condition;
@@ -44,7 +44,7 @@ public:
         Variant<NonnullOwnPtr<Condition>, Feature, GeneralEnclosed> value;
 
         bool evaluate() const;
-        DeprecatedString to_deprecated_string() const;
+        ErrorOr<String> to_string() const;
     };
 
     struct Condition {
@@ -57,7 +57,7 @@ public:
         Vector<InParens> children;
 
         bool evaluate() const;
-        DeprecatedString to_deprecated_string() const;
+        ErrorOr<String> to_string() const;
     };
 
     static NonnullRefPtr<Supports> create(NonnullOwnPtr<Condition>&& condition)
@@ -66,7 +66,7 @@ public:
     }
 
     bool matches() const { return m_matches; }
-    DeprecatedString to_deprecated_string() const;
+    ErrorOr<String> to_string() const;
 
 private:
     Supports(NonnullOwnPtr<Condition>&&);
@@ -81,6 +81,6 @@ template<>
 struct AK::Formatter<Web::CSS::Supports::InParens> : AK::Formatter<StringView> {
     ErrorOr<void> format(FormatBuilder& builder, Web::CSS::Supports::InParens const& in_parens)
     {
-        return Formatter<StringView>::format(builder, in_parens.to_deprecated_string());
+        return Formatter<StringView>::format(builder, TRY(in_parens.to_string()));
     }
 };