diff --git a/Libraries/LibWeb/CSS/CSSImageValue.cpp b/Libraries/LibWeb/CSS/CSSImageValue.cpp
index 3a9db429de2..d88be19f49f 100644
--- a/Libraries/LibWeb/CSS/CSSImageValue.cpp
+++ b/Libraries/LibWeb/CSS/CSSImageValue.cpp
@@ -7,6 +7,7 @@
 #include "CSSImageValue.h"
 #include <LibWeb/Bindings/CSSImageValuePrototype.h>
 #include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::CSS {
 
@@ -30,7 +31,7 @@ void CSSImageValue::initialize(JS::Realm& realm)
 }
 
 // https://drafts.css-houdini.org/css-typed-om-1/#stylevalue-serialization
-String CSSImageValue::to_string() const
+WebIDL::ExceptionOr<String> CSSImageValue::to_string() const
 {
     // AD-HOC: The spec doesn't say how to serialize this, as it's intentionally a black box.
     //         We just serialize the source string that was used to construct this.
diff --git a/Libraries/LibWeb/CSS/CSSImageValue.h b/Libraries/LibWeb/CSS/CSSImageValue.h
index 29e95cd2346..931f4a89b17 100644
--- a/Libraries/LibWeb/CSS/CSSImageValue.h
+++ b/Libraries/LibWeb/CSS/CSSImageValue.h
@@ -20,7 +20,7 @@ public:
 
     virtual ~CSSImageValue() override = default;
 
-    virtual String to_string() const override;
+    virtual WebIDL::ExceptionOr<String> to_string() const override;
 
 private:
     explicit CSSImageValue(JS::Realm&, String constructed_from_string);
diff --git a/Libraries/LibWeb/CSS/CSSKeywordValue.cpp b/Libraries/LibWeb/CSS/CSSKeywordValue.cpp
index 5d0c0a57413..61152ae1889 100644
--- a/Libraries/LibWeb/CSS/CSSKeywordValue.cpp
+++ b/Libraries/LibWeb/CSS/CSSKeywordValue.cpp
@@ -55,7 +55,7 @@ WebIDL::ExceptionOr<void> CSSKeywordValue::set_value(FlyString value)
 }
 
 // https://drafts.css-houdini.org/css-typed-om-1/#keywordvalue-serialization
-String CSSKeywordValue::to_string() const
+WebIDL::ExceptionOr<String> CSSKeywordValue::to_string() const
 {
     // To serialize a CSSKeywordValue this:
     // 1. Return this’s value internal slot.
diff --git a/Libraries/LibWeb/CSS/CSSKeywordValue.h b/Libraries/LibWeb/CSS/CSSKeywordValue.h
index b8837318f94..93358f4ea68 100644
--- a/Libraries/LibWeb/CSS/CSSKeywordValue.h
+++ b/Libraries/LibWeb/CSS/CSSKeywordValue.h
@@ -28,7 +28,7 @@ public:
     FlyString const& value() const { return m_value; }
     WebIDL::ExceptionOr<void> set_value(FlyString value);
 
-    virtual String to_string() const override;
+    virtual WebIDL::ExceptionOr<String> to_string() const override;
 
 private:
     explicit CSSKeywordValue(JS::Realm&, FlyString value);
diff --git a/Libraries/LibWeb/CSS/CSSNumericValue.cpp b/Libraries/LibWeb/CSS/CSSNumericValue.cpp
index ac4f2f49ccb..5ab184e2765 100644
--- a/Libraries/LibWeb/CSS/CSSNumericValue.cpp
+++ b/Libraries/LibWeb/CSS/CSSNumericValue.cpp
@@ -85,7 +85,7 @@ WebIDL::ExceptionOr<GC::Ref<CSSUnitValue>> CSSNumericValue::to(FlyString const&
     // 2. Let sum be the result of creating a sum value from this. If sum is failure, throw a TypeError.
     auto sum = create_a_sum_value();
     if (!sum.has_value())
-        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Unable to create a sum from input '{}'", to_string())) };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Unable to create a sum from input '{}'", MUST(to_string()))) };
 
     // 3. If sum has more than one item, throw a TypeError.
     //    Otherwise, let item be the result of creating a CSSUnitValue from the sole item in sum, then converting it to
@@ -94,11 +94,11 @@ WebIDL::ExceptionOr<GC::Ref<CSSUnitValue>> CSSNumericValue::to(FlyString const&
         return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Sum contains more than one item"sv };
     auto item = CSSUnitValue::create_from_sum_value_item(realm(), sum->first());
     if (!item)
-        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Unable to create CSSUnitValue from input '{}'", to_string())) };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Unable to create CSSUnitValue from input '{}'", MUST(to_string()))) };
 
     auto converted_item = item->converted_to_unit(unit);
     if (!converted_item)
-        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Unable to convert input '{}' to unit '{}'", to_string(), unit)) };
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Unable to convert input '{}' to unit '{}'", MUST(to_string()), unit)) };
 
     // 4. Return item.
     return converted_item.as_nonnull();
diff --git a/Libraries/LibWeb/CSS/CSSNumericValue.h b/Libraries/LibWeb/CSS/CSSNumericValue.h
index a01ded379d8..527e612107b 100644
--- a/Libraries/LibWeb/CSS/CSSNumericValue.h
+++ b/Libraries/LibWeb/CSS/CSSNumericValue.h
@@ -10,6 +10,7 @@
 #include <LibWeb/Bindings/CSSNumericValuePrototype.h>
 #include <LibWeb/CSS/CSSStyleValue.h>
 #include <LibWeb/CSS/NumericType.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
 #include <LibWeb/WebIDL/Types.h>
 
 namespace Web::CSS {
@@ -59,7 +60,7 @@ public:
     CSSNumericType type_for_bindings() const;
     NumericType const& type() const { return m_type; }
 
-    virtual String to_string() const final override { return to_string({}); }
+    virtual WebIDL::ExceptionOr<String> to_string() const final override { return to_string({}); }
     String to_string(SerializationParams const&) const;
 
     static WebIDL::ExceptionOr<GC::Ref<CSSNumericValue>> parse(JS::VM&, String const& css_text);
diff --git a/Libraries/LibWeb/CSS/CSSPerspective.cpp b/Libraries/LibWeb/CSS/CSSPerspective.cpp
index 3efecbd13c5..73c473e2083 100644
--- a/Libraries/LibWeb/CSS/CSSPerspective.cpp
+++ b/Libraries/LibWeb/CSS/CSSPerspective.cpp
@@ -89,13 +89,13 @@ WebIDL::ExceptionOr<Utf16String> CSSPerspective::to_string() const
     builder.append("perspective("sv);
 
     // 2. Serialize this’s length internal slot, with a minimum of 0px, and append it to s.
-    auto serialized_length = m_length.visit(
-        [](GC::Ref<CSSNumericValue> const& numeric_value) {
+    auto serialized_length = TRY(m_length.visit(
+        [](GC::Ref<CSSNumericValue> const& numeric_value) -> WebIDL::ExceptionOr<String> {
             return numeric_value->to_string({ .minimum = 0 });
         },
-        [](GC::Ref<CSSKeywordValue> const& keyword_value) {
+        [](GC::Ref<CSSKeywordValue> const& keyword_value) -> WebIDL::ExceptionOr<String> {
             return keyword_value->to_string();
-        });
+        }));
     builder.append(serialized_length);
 
     // 3. Append ")" to s, and return s.
diff --git a/Libraries/LibWeb/CSS/CSSRotate.cpp b/Libraries/LibWeb/CSS/CSSRotate.cpp
index e4f0eaebec4..e31ee913719 100644
--- a/Libraries/LibWeb/CSS/CSSRotate.cpp
+++ b/Libraries/LibWeb/CSS/CSSRotate.cpp
@@ -104,25 +104,25 @@ WebIDL::ExceptionOr<Utf16String> CSSRotate::to_string() const
         builder.append("rotate3d("sv);
 
         // 2. Serialize this’s x internal slot, and append it to s.
-        builder.append(m_x->to_string());
+        builder.append(TRY(m_x->to_string()));
 
         // 3. Append ", " to s.
         builder.append(", "sv);
 
         // 4. Serialize this’s y internal slot, and append it to s.
-        builder.append(m_y->to_string());
+        builder.append(TRY(m_y->to_string()));
 
         // 5. Append ", " to s.
         builder.append(", "sv);
 
         // 6. Serialize this’s z internal slot, and append it to s.
-        builder.append(m_z->to_string());
+        builder.append(TRY(m_z->to_string()));
 
         // 7. Append "," to s.
         builder.append(", "sv);
 
         // 8. Serialize this’s angle internal slot, and append it to s.
-        builder.append(m_angle->to_string());
+        builder.append(TRY(m_angle->to_string()));
 
         // 9. Append ")" to s, and return s.
         builder.append(")"sv);
@@ -134,7 +134,7 @@ WebIDL::ExceptionOr<Utf16String> CSSRotate::to_string() const
         builder.append("rotate("sv);
 
         // 2. Serialize this’s angle internal slot, and append it to s.
-        builder.append(m_angle->to_string());
+        builder.append(TRY(m_angle->to_string()));
 
         // 3. Append ")" to s, and return s.
         builder.append(")"sv);
diff --git a/Libraries/LibWeb/CSS/CSSScale.cpp b/Libraries/LibWeb/CSS/CSSScale.cpp
index 21052030d4e..d2f43dc96ce 100644
--- a/Libraries/LibWeb/CSS/CSSScale.cpp
+++ b/Libraries/LibWeb/CSS/CSSScale.cpp
@@ -89,19 +89,19 @@ WebIDL::ExceptionOr<Utf16String> CSSScale::to_string() const
         builder.append("scale3d("sv);
 
         // 2. Serialize this’s x internal slot, and append it to s.
-        builder.append(m_x->to_string());
+        builder.append(TRY(m_x->to_string()));
 
         // 3. Append ", " to s.
         builder.append(", "sv);
 
         // 4. Serialize this’s y internal slot, and append it to s.
-        builder.append(m_y->to_string());
+        builder.append(TRY(m_y->to_string()));
 
         // 5. Append ", " to s.
         builder.append(", "sv);
 
         // 6. Serialize this’s z internal slot, and append it to s.
-        builder.append(m_z->to_string());
+        builder.append(TRY(m_z->to_string()));
 
         // 7. Append ")" to s, and return s.
         builder.append(")"sv);
@@ -114,7 +114,7 @@ WebIDL::ExceptionOr<Utf16String> CSSScale::to_string() const
         builder.append("scale("sv);
 
         // 2. Serialize this’s x internal slot, and append it to s.
-        builder.append(m_x->to_string());
+        builder.append(TRY(m_x->to_string()));
 
         // 3. If this’s x and y internal slots are equal numeric values, append ")" to s and return s.
         if (m_x->is_equal_numeric_value(m_y)) {
@@ -126,7 +126,7 @@ WebIDL::ExceptionOr<Utf16String> CSSScale::to_string() const
         builder.append(", "sv);
 
         // 5. Serialize this’s y internal slot, and append it to s.
-        builder.append(m_y->to_string());
+        builder.append(TRY(m_y->to_string()));
 
         // 6. Append ")" to s, and return s.
         builder.append(")"sv);
diff --git a/Libraries/LibWeb/CSS/CSSSkew.cpp b/Libraries/LibWeb/CSS/CSSSkew.cpp
index a9b97392aae..28c73991b7a 100644
--- a/Libraries/LibWeb/CSS/CSSSkew.cpp
+++ b/Libraries/LibWeb/CSS/CSSSkew.cpp
@@ -67,7 +67,7 @@ WebIDL::ExceptionOr<Utf16String> CSSSkew::to_string() const
     builder.append("skew("sv);
 
     // 2. Serialize this’s ax internal slot, and append it to s.
-    builder.append(m_ax->to_string());
+    builder.append(TRY(m_ax->to_string()));
 
     // 3. If this’s ay internal slot is a CSSUnitValue with a value of 0, then append ")" to s and return s.
     if (auto* ay_unit_value = as_if<CSSUnitValue>(*m_ay); ay_unit_value && ay_unit_value->value() == 0) {
@@ -79,7 +79,7 @@ WebIDL::ExceptionOr<Utf16String> CSSSkew::to_string() const
     builder.append(", "sv);
 
     // 5. Serialize this’s ay internal slot, and append it to s.
-    builder.append(m_ay->to_string());
+    builder.append(TRY(m_ay->to_string()));
 
     // 6. Append ")" to s, and return s.
     builder.append(")"sv);
diff --git a/Libraries/LibWeb/CSS/CSSSkewX.cpp b/Libraries/LibWeb/CSS/CSSSkewX.cpp
index 86599142d7c..bcd52447d50 100644
--- a/Libraries/LibWeb/CSS/CSSSkewX.cpp
+++ b/Libraries/LibWeb/CSS/CSSSkewX.cpp
@@ -62,7 +62,7 @@ WebIDL::ExceptionOr<Utf16String> CSSSkewX::to_string() const
     builder.append("skewX("sv);
 
     // 2. Serialize this’s ax internal slot, and append it to s.
-    builder.append(m_ax->to_string());
+    builder.append(TRY(m_ax->to_string()));
 
     // 3. Append ")" to s, and return s.
     builder.append(")"sv);
diff --git a/Libraries/LibWeb/CSS/CSSSkewY.cpp b/Libraries/LibWeb/CSS/CSSSkewY.cpp
index 363f98565f6..4906ba345ca 100644
--- a/Libraries/LibWeb/CSS/CSSSkewY.cpp
+++ b/Libraries/LibWeb/CSS/CSSSkewY.cpp
@@ -62,7 +62,7 @@ WebIDL::ExceptionOr<Utf16String> CSSSkewY::to_string() const
     builder.append("skewY("sv);
 
     // 2. Serialize this’s ay internal slot, and append it to s.
-    builder.append(m_ay->to_string());
+    builder.append(TRY(m_ay->to_string()));
 
     // 3. Append ")" to s, and return s.
     builder.append(")"sv);
diff --git a/Libraries/LibWeb/CSS/CSSStyleValue.cpp b/Libraries/LibWeb/CSS/CSSStyleValue.cpp
index e731b89d0f7..666954d5d80 100644
--- a/Libraries/LibWeb/CSS/CSSStyleValue.cpp
+++ b/Libraries/LibWeb/CSS/CSSStyleValue.cpp
@@ -92,7 +92,7 @@ WebIDL::ExceptionOr<Variant<GC::Ref<CSSStyleValue>, GC::RootVector<GC::Ref<CSSSt
 }
 
 // https://drafts.css-houdini.org/css-typed-om-1/#stylevalue-serialization
-String CSSStyleValue::to_string() const
+WebIDL::ExceptionOr<String> CSSStyleValue::to_string() const
 {
     // if the value was constructed from a USVString
     if (m_constructed_from_string.has_value()) {
@@ -108,7 +108,7 @@ String CSSStyleValue::to_string() const
     {
         // the serialization is specified in §6.7 Serialization from CSSOM Values below.
     }
-    return {};
+    return String {};
 }
 
 }
diff --git a/Libraries/LibWeb/CSS/CSSStyleValue.h b/Libraries/LibWeb/CSS/CSSStyleValue.h
index 74ad0d3113a..815cff100d1 100644
--- a/Libraries/LibWeb/CSS/CSSStyleValue.h
+++ b/Libraries/LibWeb/CSS/CSSStyleValue.h
@@ -25,7 +25,7 @@ public:
     static WebIDL::ExceptionOr<GC::Ref<CSSStyleValue>> parse(JS::VM&, String property, String css_text);
     static WebIDL::ExceptionOr<GC::RootVector<GC::Ref<CSSStyleValue>>> parse_all(JS::VM&, String property, String css_text);
 
-    virtual String to_string() const;
+    virtual WebIDL::ExceptionOr<String> to_string() const;
 
 protected:
     explicit CSSStyleValue(JS::Realm&);
diff --git a/Libraries/LibWeb/CSS/CSSTranslate.cpp b/Libraries/LibWeb/CSS/CSSTranslate.cpp
index b282743c092..962c09da8d5 100644
--- a/Libraries/LibWeb/CSS/CSSTranslate.cpp
+++ b/Libraries/LibWeb/CSS/CSSTranslate.cpp
@@ -87,19 +87,19 @@ WebIDL::ExceptionOr<Utf16String> CSSTranslate::to_string() const
         builder.append("translate3d("sv);
 
         // 2. Serialize this’s x internal slot, and append it to s.
-        builder.append(m_x->to_string());
+        builder.append(TRY(m_x->to_string()));
 
         // 3. Append ", " to s.
         builder.append(", "sv);
 
         // 4. Serialize this’s y internal slot, and append it to s.
-        builder.append(m_y->to_string());
+        builder.append(TRY(m_y->to_string()));
 
         // 5. Append ", " to s.
         builder.append(", "sv);
 
         // 6. Serialize this’s z internal slot, and append it to s.
-        builder.append(m_z->to_string());
+        builder.append(TRY(m_z->to_string()));
 
         // 7. Append ")" to s, and return s.
         builder.append(")"sv);
@@ -111,13 +111,13 @@ WebIDL::ExceptionOr<Utf16String> CSSTranslate::to_string() const
         builder.append("translate("sv);
 
         // 2. Serialize this’s x internal slot, and append it to s.
-        builder.append(m_x->to_string());
+        builder.append(TRY(m_x->to_string()));
 
         // 3. Append ", " to s.
         builder.append(", "sv);
 
         // 4. Serialize this’s y internal slot, and append it to s.
-        builder.append(m_y->to_string());
+        builder.append(TRY(m_y->to_string()));
 
         // 5. Append ")" to s, and return s.
         builder.append(")"sv);
diff --git a/Libraries/LibWeb/CSS/CSSUnparsedValue.cpp b/Libraries/LibWeb/CSS/CSSUnparsedValue.cpp
index 996bd6c3931..d3c38a0b9ad 100644
--- a/Libraries/LibWeb/CSS/CSSUnparsedValue.cpp
+++ b/Libraries/LibWeb/CSS/CSSUnparsedValue.cpp
@@ -116,7 +116,7 @@ WebIDL::ExceptionOr<void> CSSUnparsedValue::set_value_of_new_indexed_property(u3
 }
 
 // https://drafts.css-houdini.org/css-typed-om-1/#serialize-a-cssunparsedvalue
-String CSSUnparsedValue::to_string() const
+WebIDL::ExceptionOr<String> CSSUnparsedValue::to_string() const
 {
     // To serialize a CSSUnparsedValue this:
     // 1. Let s initially be the empty string.
@@ -126,15 +126,17 @@ String CSSUnparsedValue::to_string() const
     for (auto const& item : m_tokens) {
         // FIXME: In order to match the expected test behaviour, this should insert comments, with the same rules as
         //        serialize_a_series_of_component_values(). See https://github.com/w3c/css-houdini-drafts/issues/1148
-        item.visit(
+        TRY(item.visit(
             // 1. If item is a USVString, append it to s.
-            [&](String const& string) {
+            [&](String const& string) -> WebIDL::ExceptionOr<void> {
                 s.append(string);
+                return {};
             },
             // 2. Otherwise, item is a CSSVariableReferenceValue. Serialize it, then append the result to s.
-            [&](GC::Ref<CSSVariableReferenceValue> const& variable) {
-                s.append(variable->to_string());
-            });
+            [&](GC::Ref<CSSVariableReferenceValue> const& variable) -> WebIDL::ExceptionOr<void> {
+                s.append(TRY(variable->to_string()));
+                return {};
+            }));
     }
 
     // 3. Return s.
diff --git a/Libraries/LibWeb/CSS/CSSUnparsedValue.h b/Libraries/LibWeb/CSS/CSSUnparsedValue.h
index 6cd283fedaa..32e5b2ea7be 100644
--- a/Libraries/LibWeb/CSS/CSSUnparsedValue.h
+++ b/Libraries/LibWeb/CSS/CSSUnparsedValue.h
@@ -30,7 +30,7 @@ public:
     virtual WebIDL::ExceptionOr<void> set_value_of_existing_indexed_property(u32, JS::Value) override;
     virtual WebIDL::ExceptionOr<void> set_value_of_new_indexed_property(u32, JS::Value) override;
 
-    virtual String to_string() const override;
+    virtual WebIDL::ExceptionOr<String> to_string() const override;
 
 private:
     explicit CSSUnparsedValue(JS::Realm&, Vector<CSSUnparsedSegment>);
diff --git a/Libraries/LibWeb/CSS/CSSVariableReferenceValue.cpp b/Libraries/LibWeb/CSS/CSSVariableReferenceValue.cpp
index f87de0b7583..da62614c7b1 100644
--- a/Libraries/LibWeb/CSS/CSSVariableReferenceValue.cpp
+++ b/Libraries/LibWeb/CSS/CSSVariableReferenceValue.cpp
@@ -89,7 +89,7 @@ WebIDL::ExceptionOr<void> CSSVariableReferenceValue::set_fallback(GC::Ptr<CSSUnp
 }
 
 // https://drafts.css-houdini.org/css-typed-om-1/#serialize-a-cssvariablereferencevalue
-String CSSVariableReferenceValue::to_string() const
+WebIDL::ExceptionOr<String> CSSVariableReferenceValue::to_string() const
 {
     // To serialize a CSSVariableReferenceValue this:
     // 1. Let s initially be "var(".
@@ -103,7 +103,7 @@ String CSSVariableReferenceValue::to_string() const
     if (m_fallback) {
         // AD-HOC: Tested behaviour requires we append "," without the space. https://github.com/w3c/css-houdini-drafts/issues/1148
         s.append(","sv);
-        s.append(m_fallback->to_string());
+        s.append(TRY(m_fallback->to_string()));
     }
 
     // 4. Append ")" to s and return s.
diff --git a/Libraries/LibWeb/CSS/CSSVariableReferenceValue.h b/Libraries/LibWeb/CSS/CSSVariableReferenceValue.h
index 5a430cb1cc9..30f52c4b576 100644
--- a/Libraries/LibWeb/CSS/CSSVariableReferenceValue.h
+++ b/Libraries/LibWeb/CSS/CSSVariableReferenceValue.h
@@ -27,7 +27,7 @@ public:
     GC::Ptr<CSSUnparsedValue> fallback() const;
     WebIDL::ExceptionOr<void> set_fallback(GC::Ptr<CSSUnparsedValue>);
 
-    String to_string() const;
+    WebIDL::ExceptionOr<String> to_string() const;
 
 private:
     CSSVariableReferenceValue(JS::Realm&, FlyString variable, GC::Ptr<CSSUnparsedValue> fallback);