diff --git a/Userland/Libraries/LibWeb/Bindings/PlatformObject.cpp b/Userland/Libraries/LibWeb/Bindings/PlatformObject.cpp
index 8027ae84a3e..b989def3399 100644
--- a/Userland/Libraries/LibWeb/Bindings/PlatformObject.cpp
+++ b/Userland/Libraries/LibWeb/Bindings/PlatformObject.cpp
@@ -501,9 +501,9 @@ bool PlatformObject::is_supported_property_name(FlyString const& name) const
     return supported_property_names().contains_slow(name);
 }
 
-bool PlatformObject::is_supported_property_index(u32) const
+bool PlatformObject::is_supported_property_index(u32 index) const
 {
-    return false;
+    return item_value(index).has_value();
 }
 
 }
diff --git a/Userland/Libraries/LibWeb/Bindings/PlatformObject.h b/Userland/Libraries/LibWeb/Bindings/PlatformObject.h
index f405206904e..cd0610a01cc 100644
--- a/Userland/Libraries/LibWeb/Bindings/PlatformObject.h
+++ b/Userland/Libraries/LibWeb/Bindings/PlatformObject.h
@@ -76,7 +76,7 @@ protected:
     virtual JS::Value named_item_value(FlyString const& name) const;
     virtual Vector<FlyString> supported_property_names() const;
     virtual bool is_supported_property_name(FlyString const&) const;
-    virtual bool is_supported_property_index(u32) const;
+    bool is_supported_property_index(u32) const;
 
     // NOTE: These will crash if you make has_named_property_setter return true but do not override these methods.
     // NOTE: This is only used if named_property_setter_has_identifier returns false, otherwise set_value_of_named_property is used instead.
diff --git a/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp b/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
index 4b1bf4168d8..e259b84c086 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
@@ -51,13 +51,6 @@ void CSSRuleList::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_rules);
 }
 
-bool CSSRuleList::is_supported_property_index(u32 index) const
-{
-    // The object’s supported property indices are the numbers in the range zero to one less than the number of CSSRule objects represented by the collection.
-    // If there are no such CSSRule objects, then there are no supported property indices.
-    return index < m_rules.size();
-}
-
 // https://www.w3.org/TR/cssom/#insert-a-css-rule
 WebIDL::ExceptionOr<unsigned> CSSRuleList::insert_a_css_rule(Variant<StringView, CSSRule*> rule, u32 index)
 {
diff --git a/Userland/Libraries/LibWeb/CSS/CSSRuleList.h b/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
index e72e7eab5a2..00eb564f4ba 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
@@ -51,7 +51,6 @@ public:
     auto end() const { return m_rules.end(); }
     auto end() { return m_rules.end(); }
 
-    virtual bool is_supported_property_index(u32 index) const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
 
     WebIDL::ExceptionOr<void> remove_a_css_rule(u32 index);
diff --git a/Userland/Libraries/LibWeb/CSS/MediaList.cpp b/Userland/Libraries/LibWeb/CSS/MediaList.cpp
index 65a6b6839f9..b1dc77dfa9d 100644
--- a/Userland/Libraries/LibWeb/CSS/MediaList.cpp
+++ b/Userland/Libraries/LibWeb/CSS/MediaList.cpp
@@ -48,15 +48,10 @@ void MediaList::set_media_text(StringView text)
     m_media = parse_media_query_list(Parser::ParsingContext { realm() }, text);
 }
 
-bool MediaList::is_supported_property_index(u32 index) const
-{
-    return index < length();
-}
-
 // https://www.w3.org/TR/cssom-1/#dom-medialist-item
 Optional<String> MediaList::item(u32 index) const
 {
-    if (!is_supported_property_index(index))
+    if (index >= m_media.size())
         return {};
 
     return m_media[index]->to_string();
diff --git a/Userland/Libraries/LibWeb/CSS/MediaList.h b/Userland/Libraries/LibWeb/CSS/MediaList.h
index 5cd6605aac3..62cbbce6b35 100644
--- a/Userland/Libraries/LibWeb/CSS/MediaList.h
+++ b/Userland/Libraries/LibWeb/CSS/MediaList.h
@@ -31,7 +31,6 @@ public:
     void append_medium(StringView);
     void delete_medium(StringView);
 
-    virtual bool is_supported_property_index(u32 index) const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
 
     bool evaluate(HTML::Window const&);
diff --git a/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp b/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp
index 0f87852260e..5bfa991df73 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp
@@ -153,17 +153,6 @@ void StyleSheetList::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_sheets);
 }
 
-// https://www.w3.org/TR/cssom/#ref-for-dfn-supported-property-indices%E2%91%A1
-bool StyleSheetList::is_supported_property_index(u32 index) const
-{
-    // The object’s supported property indices are the numbers in the range zero to one less than the number of CSS style sheets represented by the collection.
-    // If there are no such CSS style sheets, then there are no supported property indices.
-    if (m_sheets.is_empty())
-        return false;
-
-    return index < m_sheets.size();
-}
-
 Optional<JS::Value> StyleSheetList::item_value(size_t index) const
 {
     if (index >= m_sheets.size())
diff --git a/Userland/Libraries/LibWeb/CSS/StyleSheetList.h b/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
index dbeaf777975..d4257b54ab7 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
@@ -35,7 +35,6 @@ public:
 
     size_t length() const { return m_sheets.size(); }
 
-    virtual bool is_supported_property_index(u32 index) const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
 
     DOM::Document& document() { return m_document; }
diff --git a/Userland/Libraries/LibWeb/DOM/DOMTokenList.cpp b/Userland/Libraries/LibWeb/DOM/DOMTokenList.cpp
index 7f40da16008..8d818f7a9e7 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMTokenList.cpp
+++ b/Userland/Libraries/LibWeb/DOM/DOMTokenList.cpp
@@ -98,12 +98,6 @@ void DOMTokenList::associated_attribute_changed(StringView value)
         append_to_ordered_set(m_token_set, String::from_utf8(split_value).release_value_but_fixme_should_propagate_errors());
 }
 
-// https://dom.spec.whatwg.org/#ref-for-dfn-supported-property-indices%E2%91%A3
-bool DOMTokenList::is_supported_property_index(u32 index) const
-{
-    return index < m_token_set.size();
-}
-
 // https://dom.spec.whatwg.org/#dom-domtokenlist-item
 Optional<String> DOMTokenList::item(size_t index) const
 {
diff --git a/Userland/Libraries/LibWeb/DOM/DOMTokenList.h b/Userland/Libraries/LibWeb/DOM/DOMTokenList.h
index e0946ef1b66..7bbf0958ada 100644
--- a/Userland/Libraries/LibWeb/DOM/DOMTokenList.h
+++ b/Userland/Libraries/LibWeb/DOM/DOMTokenList.h
@@ -30,7 +30,6 @@ public:
 
     void associated_attribute_changed(StringView value);
 
-    virtual bool is_supported_property_index(u32 index) const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
 
     size_t length() const { return m_token_set.size(); }
diff --git a/Userland/Libraries/LibWeb/DOM/HTMLCollection.cpp b/Userland/Libraries/LibWeb/DOM/HTMLCollection.cpp
index ba06296469d..8b40378ffe6 100644
--- a/Userland/Libraries/LibWeb/DOM/HTMLCollection.cpp
+++ b/Userland/Libraries/LibWeb/DOM/HTMLCollection.cpp
@@ -161,14 +161,6 @@ Vector<FlyString> HTMLCollection::supported_property_names() const
     return result;
 }
 
-// https://dom.spec.whatwg.org/#ref-for-dfn-supported-property-indices%E2%91%A1
-bool HTMLCollection::is_supported_property_index(u32 index) const
-{
-    // The object’s supported property indices are the numbers in the range zero to one less than the number of elements represented by the collection.
-    // If there are no such elements, then there are no supported property indices.
-    return index < length();
-}
-
 Optional<JS::Value> HTMLCollection::item_value(size_t index) const
 {
     auto* element = item(index);
diff --git a/Userland/Libraries/LibWeb/DOM/HTMLCollection.h b/Userland/Libraries/LibWeb/DOM/HTMLCollection.h
index 9fa3759a468..95a7ff977d9 100644
--- a/Userland/Libraries/LibWeb/DOM/HTMLCollection.h
+++ b/Userland/Libraries/LibWeb/DOM/HTMLCollection.h
@@ -44,7 +44,6 @@ public:
     virtual JS::Value named_item_value(FlyString const& name) const override;
     virtual Vector<FlyString> supported_property_names() const override;
     virtual bool is_supported_property_name(FlyString const&) const override;
-    virtual bool is_supported_property_index(u32) const override;
 
 protected:
     HTMLCollection(ParentNode& root, Scope, ESCAPING Function<bool(Element const&)> filter);
diff --git a/Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp b/Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp
index 417a9de1c84..f4a2f459b88 100644
--- a/Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp
+++ b/Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp
@@ -93,12 +93,4 @@ Node const* LiveNodeList::item(u32 index) const
     return nodes[index];
 }
 
-// https://dom.spec.whatwg.org/#ref-for-dfn-supported-property-indices
-bool LiveNodeList::is_supported_property_index(u32 index) const
-{
-    // The object’s supported property indices are the numbers in the range zero to one less than the number of nodes represented by the collection.
-    // If there are no such elements, then there are no supported property indices.
-    return index < length();
-}
-
 }
diff --git a/Userland/Libraries/LibWeb/DOM/LiveNodeList.h b/Userland/Libraries/LibWeb/DOM/LiveNodeList.h
index aa40045ff1c..0e1dc68a0e9 100644
--- a/Userland/Libraries/LibWeb/DOM/LiveNodeList.h
+++ b/Userland/Libraries/LibWeb/DOM/LiveNodeList.h
@@ -30,8 +30,6 @@ public:
     virtual u32 length() const override;
     virtual Node const* item(u32 index) const override;
 
-    virtual bool is_supported_property_index(u32) const override;
-
 protected:
     LiveNodeList(JS::Realm&, Node const& root, Scope, ESCAPING Function<bool(Node const&)> filter);
 
diff --git a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
index 30163d9df38..7bd739d6bdb 100644
--- a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
+++ b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp
@@ -47,12 +47,6 @@ void NamedNodeMap::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_attributes);
 }
 
-// https://dom.spec.whatwg.org/#ref-for-dfn-supported-property-indices%E2%91%A3
-bool NamedNodeMap::is_supported_property_index(u32 index) const
-{
-    return index < m_attributes.size();
-}
-
 // https://dom.spec.whatwg.org/#ref-for-dfn-supported-property-names%E2%91%A0
 Vector<FlyString> NamedNodeMap::supported_property_names() const
 {
diff --git a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
index c2aca66fb79..842a85df3f0 100644
--- a/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
+++ b/Userland/Libraries/LibWeb/DOM/NamedNodeMap.h
@@ -24,7 +24,6 @@ public:
     [[nodiscard]] static JS::NonnullGCPtr<NamedNodeMap> create(Element&);
     ~NamedNodeMap() = default;
 
-    virtual bool is_supported_property_index(u32 index) const override;
     virtual Vector<FlyString> supported_property_names() const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
     virtual JS::Value named_item_value(FlyString const& name) const override;
diff --git a/Userland/Libraries/LibWeb/DOM/NodeList.cpp b/Userland/Libraries/LibWeb/DOM/NodeList.cpp
index 5e32e06cf76..1520f7811f5 100644
--- a/Userland/Libraries/LibWeb/DOM/NodeList.cpp
+++ b/Userland/Libraries/LibWeb/DOM/NodeList.cpp
@@ -33,9 +33,4 @@ Optional<JS::Value> NodeList::item_value(size_t index) const
     return const_cast<Node*>(node);
 }
 
-bool NodeList::is_supported_property_index(u32 index) const
-{
-    return index < length();
-}
-
 }
diff --git a/Userland/Libraries/LibWeb/DOM/NodeList.h b/Userland/Libraries/LibWeb/DOM/NodeList.h
index 6f7eee8a276..bbc79ead14f 100644
--- a/Userland/Libraries/LibWeb/DOM/NodeList.h
+++ b/Userland/Libraries/LibWeb/DOM/NodeList.h
@@ -22,7 +22,6 @@ public:
     virtual Node const* item(u32 index) const = 0;
 
     virtual Optional<JS::Value> item_value(size_t index) const override;
-    virtual bool is_supported_property_index(u32) const override;
 
 protected:
     explicit NodeList(JS::Realm&);
diff --git a/Userland/Libraries/LibWeb/DOM/StaticNodeList.cpp b/Userland/Libraries/LibWeb/DOM/StaticNodeList.cpp
index 64e15de88a4..1625c8254df 100644
--- a/Userland/Libraries/LibWeb/DOM/StaticNodeList.cpp
+++ b/Userland/Libraries/LibWeb/DOM/StaticNodeList.cpp
@@ -47,12 +47,4 @@ Node const* StaticNodeList::item(u32 index) const
     return m_static_nodes[index];
 }
 
-// https://dom.spec.whatwg.org/#ref-for-dfn-supported-property-indices
-bool StaticNodeList::is_supported_property_index(u32 index) const
-{
-    // The object’s supported property indices are the numbers in the range zero to one less than the number of nodes represented by the collection.
-    // If there are no such elements, then there are no supported property indices.
-    return index < m_static_nodes.size();
-}
-
 }
diff --git a/Userland/Libraries/LibWeb/DOM/StaticNodeList.h b/Userland/Libraries/LibWeb/DOM/StaticNodeList.h
index 5ed9b75e578..784c354f989 100644
--- a/Userland/Libraries/LibWeb/DOM/StaticNodeList.h
+++ b/Userland/Libraries/LibWeb/DOM/StaticNodeList.h
@@ -23,8 +23,6 @@ public:
     virtual u32 length() const override;
     virtual Node const* item(u32 index) const override;
 
-    virtual bool is_supported_property_index(u32) const override;
-
 private:
     StaticNodeList(JS::Realm&, Vector<JS::Handle<Node>>);
 
diff --git a/Userland/Libraries/LibWeb/FileAPI/FileList.cpp b/Userland/Libraries/LibWeb/FileAPI/FileList.cpp
index 10373c4f2e8..2384f3ce235 100644
--- a/Userland/Libraries/LibWeb/FileAPI/FileList.cpp
+++ b/Userland/Libraries/LibWeb/FileAPI/FileList.cpp
@@ -45,17 +45,6 @@ void FileList::initialize(JS::Realm& realm)
     WEB_SET_PROTOTYPE_FOR_INTERFACE(FileList);
 }
 
-// https://w3c.github.io/FileAPI/#dfn-item
-bool FileList::is_supported_property_index(u32 index) const
-{
-    // Supported property indices are the numbers in the range zero to one less than the number of File objects represented by the FileList object.
-    // If there are no such File objects, then there are no supported property indices.
-    if (m_files.is_empty())
-        return false;
-
-    return index < m_files.size();
-}
-
 Optional<JS::Value> FileList::item_value(size_t index) const
 {
     if (index >= m_files.size())
diff --git a/Userland/Libraries/LibWeb/FileAPI/FileList.h b/Userland/Libraries/LibWeb/FileAPI/FileList.h
index cbde90af67a..0226c2c8d22 100644
--- a/Userland/Libraries/LibWeb/FileAPI/FileList.h
+++ b/Userland/Libraries/LibWeb/FileAPI/FileList.h
@@ -42,7 +42,6 @@ public:
         return index < m_files.size() ? m_files[index].ptr() : nullptr;
     }
 
-    virtual bool is_supported_property_index(u32 index) const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
 
     virtual StringView interface_name() const override { return "FileList"sv; }
diff --git a/Userland/Libraries/LibWeb/Geometry/DOMRectList.cpp b/Userland/Libraries/LibWeb/Geometry/DOMRectList.cpp
index ce5b142bb34..f7d3d59ba66 100644
--- a/Userland/Libraries/LibWeb/Geometry/DOMRectList.cpp
+++ b/Userland/Libraries/LibWeb/Geometry/DOMRectList.cpp
@@ -61,11 +61,6 @@ DOMRect const* DOMRectList::item(u32 index) const
     return m_rects[index];
 }
 
-bool DOMRectList::is_supported_property_index(u32 index) const
-{
-    return index < m_rects.size();
-}
-
 Optional<JS::Value> DOMRectList::item_value(size_t index) const
 {
     if (index >= m_rects.size())
diff --git a/Userland/Libraries/LibWeb/Geometry/DOMRectList.h b/Userland/Libraries/LibWeb/Geometry/DOMRectList.h
index 415c0a90f64..10f6bb4b2f5 100644
--- a/Userland/Libraries/LibWeb/Geometry/DOMRectList.h
+++ b/Userland/Libraries/LibWeb/Geometry/DOMRectList.h
@@ -26,7 +26,6 @@ public:
     u32 length() const;
     DOMRect const* item(u32 index) const;
 
-    virtual bool is_supported_property_index(u32) const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
 
 private:
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLAllCollection.cpp b/Userland/Libraries/LibWeb/HTML/HTMLAllCollection.cpp
index d12dc6073cb..92dfff2b648 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLAllCollection.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLAllCollection.cpp
@@ -214,11 +214,6 @@ Variant<JS::NonnullGCPtr<DOM::HTMLCollection>, JS::NonnullGCPtr<DOM::Element>, E
     return get_the_all_named_elements(MUST(FlyString::from_deprecated_fly_string(name_or_index.as_string())));
 }
 
-bool HTMLAllCollection::is_supported_property_index(u32 index) const
-{
-    return index < collect_matching_elements().size();
-}
-
 Optional<JS::Value> HTMLAllCollection::item_value(size_t index) const
 {
     if (auto value = get_the_all_indexed_element(index))
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLAllCollection.h b/Userland/Libraries/LibWeb/HTML/HTMLAllCollection.h
index c81b64b154b..9c443a6c7c1 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLAllCollection.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLAllCollection.h
@@ -37,7 +37,6 @@ public:
     virtual Optional<JS::Value> item_value(size_t index) const override;
     virtual JS::Value named_item_value(FlyString const& name) const override;
     virtual Vector<FlyString> supported_property_names() const override;
-    virtual bool is_supported_property_index(u32) const override;
 
 protected:
     HTMLAllCollection(DOM::ParentNode& root, Scope, ESCAPING Function<bool(DOM::Element const&)> filter);
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLFormElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLFormElement.cpp
index 8fc6283f219..43e4d5a4e89 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLFormElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLFormElement.cpp
@@ -927,13 +927,6 @@ void HTMLFormElement::plan_to_navigate_to(URL::URL url, Variant<Empty, String, P
     VERIFY(m_planned_navigation);
 }
 
-// https://html.spec.whatwg.org/multipage/forms.html#the-form-element:supported-property-indices
-bool HTMLFormElement::is_supported_property_index(u32 index) const
-{
-    // The supported property indices at any instant are the indices supported by the object returned by the elements attribute at that instant.
-    return index < elements()->length();
-}
-
 // https://html.spec.whatwg.org/multipage/forms.html#dom-form-item
 Optional<JS::Value> HTMLFormElement::item_value(size_t index) const
 {
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLFormElement.h b/Userland/Libraries/LibWeb/HTML/HTMLFormElement.h
index b8e68327db1..cc1ef50d3f8 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLFormElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLFormElement.h
@@ -109,7 +109,6 @@ private:
     virtual Optional<JS::Value> item_value(size_t index) const override;
     virtual JS::Value named_item_value(FlyString const& name) const override;
     virtual Vector<FlyString> supported_property_names() const override;
-    virtual bool is_supported_property_index(u32) const override;
 
     virtual void attribute_changed(FlyString const& name, Optional<String> const& old_value, Optional<String> const& value) override;
 
diff --git a/Userland/Libraries/LibWeb/HTML/MimeTypeArray.cpp b/Userland/Libraries/LibWeb/HTML/MimeTypeArray.cpp
index 99d94dbf782..fc06bfee83b 100644
--- a/Userland/Libraries/LibWeb/HTML/MimeTypeArray.cpp
+++ b/Userland/Libraries/LibWeb/HTML/MimeTypeArray.cpp
@@ -50,14 +50,6 @@ Vector<FlyString> MimeTypeArray::supported_property_names() const
     return mime_types;
 }
 
-// https://html.spec.whatwg.org/multipage/system-state.html#pdf-viewing-support:supports-indexed-properties-2
-bool MimeTypeArray::is_supported_property_index(u32 index) const
-{
-    // The MimeTypeArray interface supports indexed properties. The supported property indices are the indices of this's relevant global object's PDF viewer mime type objects.
-    auto& window = verify_cast<HTML::Window>(HTML::relevant_global_object(*this));
-    return index < window.pdf_viewer_mime_type_objects().size();
-}
-
 // https://html.spec.whatwg.org/multipage/system-state.html#dom-mimetypearray-length
 size_t MimeTypeArray::length() const
 {
diff --git a/Userland/Libraries/LibWeb/HTML/MimeTypeArray.h b/Userland/Libraries/LibWeb/HTML/MimeTypeArray.h
index ea32f2bacd7..83213ca2bc4 100644
--- a/Userland/Libraries/LibWeb/HTML/MimeTypeArray.h
+++ b/Userland/Libraries/LibWeb/HTML/MimeTypeArray.h
@@ -31,7 +31,6 @@ private:
     virtual Vector<FlyString> supported_property_names() const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
     virtual JS::Value named_item_value(FlyString const& name) const override;
-    virtual bool is_supported_property_index(u32) const override;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Plugin.cpp b/Userland/Libraries/LibWeb/HTML/Plugin.cpp
index 11cf3d32c00..458b9a8e6b6 100644
--- a/Userland/Libraries/LibWeb/HTML/Plugin.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Plugin.cpp
@@ -74,14 +74,6 @@ Vector<FlyString> Plugin::supported_property_names() const
     return mime_types;
 }
 
-// https://html.spec.whatwg.org/multipage/system-state.html#pdf-viewing-support:supports-indexed-properties-3
-bool Plugin::is_supported_property_index(u32 index) const
-{
-    // The Plugin interface supports indexed properties. The supported property indices are the indices of this's relevant global object's PDF viewer mime type objects.
-    auto& window = verify_cast<HTML::Window>(HTML::relevant_global_object(*this));
-    return index < window.pdf_viewer_mime_type_objects().size();
-}
-
 // https://html.spec.whatwg.org/multipage/system-state.html#dom-plugin-length
 size_t Plugin::length() const
 {
diff --git a/Userland/Libraries/LibWeb/HTML/Plugin.h b/Userland/Libraries/LibWeb/HTML/Plugin.h
index 04e2793dd62..3fc348c4d8a 100644
--- a/Userland/Libraries/LibWeb/HTML/Plugin.h
+++ b/Userland/Libraries/LibWeb/HTML/Plugin.h
@@ -37,7 +37,6 @@ private:
     virtual Vector<FlyString> supported_property_names() const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
     virtual JS::Value named_item_value(FlyString const& name) const override;
-    virtual bool is_supported_property_index(u32) const override;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/PluginArray.cpp b/Userland/Libraries/LibWeb/HTML/PluginArray.cpp
index 170121cab82..7453d6e8e7c 100644
--- a/Userland/Libraries/LibWeb/HTML/PluginArray.cpp
+++ b/Userland/Libraries/LibWeb/HTML/PluginArray.cpp
@@ -59,14 +59,6 @@ Vector<FlyString> PluginArray::supported_property_names() const
     return plugin_names;
 }
 
-// https://html.spec.whatwg.org/multipage/system-state.html#pdf-viewing-support:supports-indexed-properties
-bool PluginArray::is_supported_property_index(u32 index) const
-{
-    // The PluginArray interface supports indexed properties. The supported property indices are the indices of this's relevant global object's PDF viewer plugin objects.
-    auto& window = verify_cast<HTML::Window>(HTML::relevant_global_object(*this));
-    return index < window.pdf_viewer_plugin_objects().size();
-}
-
 // https://html.spec.whatwg.org/multipage/system-state.html#dom-pluginarray-length
 size_t PluginArray::length() const
 {
diff --git a/Userland/Libraries/LibWeb/HTML/PluginArray.h b/Userland/Libraries/LibWeb/HTML/PluginArray.h
index 0aba112d2db..dd5e37b1012 100644
--- a/Userland/Libraries/LibWeb/HTML/PluginArray.h
+++ b/Userland/Libraries/LibWeb/HTML/PluginArray.h
@@ -32,7 +32,6 @@ private:
     virtual Vector<FlyString> supported_property_names() const override;
     virtual Optional<JS::Value> item_value(size_t index) const override;
     virtual JS::Value named_item_value(FlyString const& name) const override;
-    virtual bool is_supported_property_index(u32) const override;
 };
 
 }