diff --git a/Userland/Libraries/LibWeb/DOM/Element.cpp b/Userland/Libraries/LibWeb/DOM/Element.cpp
index 37cff6ec5f..dae0af495b 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Element.cpp
@@ -34,6 +34,7 @@ Element::Element(Document& document, QualifiedName qualified_name)
     : ParentNode(document, NodeType::ELEMENT_NODE)
     , m_qualified_name(move(qualified_name))
 {
+    make_html_uppercased_qualified_name();
 }
 
 Element::~Element()
@@ -359,4 +360,14 @@ NonnullRefPtr<CSS::CSSStyleDeclaration> Element::style_for_bindings()
     return *m_inline_style;
 }
 
+// https://dom.spec.whatwg.org/#element-html-uppercased-qualified-name
+void Element::make_html_uppercased_qualified_name()
+{
+    // This is allowed by the spec: "User agents could optimize qualified name and HTML-uppercased qualified name by storing them in internal slots."
+    if (namespace_() == Namespace::HTML /* FIXME: and its node document is an HTML document */)
+        m_html_uppercased_qualified_name = qualified_name().to_uppercase();
+    else
+        m_html_uppercased_qualified_name = qualified_name();
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/DOM/Element.h b/Userland/Libraries/LibWeb/DOM/Element.h
index 189363a99f..bcf693e6d7 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.h
+++ b/Userland/Libraries/LibWeb/DOM/Element.h
@@ -29,7 +29,9 @@ public:
     Element(Document&, QualifiedName);
     virtual ~Element() override;
 
-    virtual FlyString node_name() const final { return m_qualified_name.local_name(); }
+    const String& qualified_name() const { return m_qualified_name.as_string(); }
+    String html_uppercased_qualified_name() const { return m_html_uppercased_qualified_name; }
+    virtual FlyString node_name() const final { return html_uppercased_qualified_name(); }
     const FlyString& local_name() const { return m_qualified_name.local_name(); }
 
     // NOTE: This is for the JS bindings
@@ -96,7 +98,10 @@ private:
     Attribute* find_attribute(const FlyString& name);
     const Attribute* find_attribute(const FlyString& name) const;
 
+    void make_html_uppercased_qualified_name();
+
     QualifiedName m_qualified_name;
+    String m_html_uppercased_qualified_name;
     Vector<Attribute> m_attributes;
 
     RefPtr<CSS::CSSStyleDeclaration> m_inline_style;
diff --git a/Userland/Libraries/LibWeb/QualifiedName.h b/Userland/Libraries/LibWeb/QualifiedName.h
index c956bc804c..c7c429d2d3 100644
--- a/Userland/Libraries/LibWeb/QualifiedName.h
+++ b/Userland/Libraries/LibWeb/QualifiedName.h
@@ -17,16 +17,33 @@ public:
         , m_prefix(prefix)
         , m_namespace(namespace_)
     {
+        make_internal_string();
     }
 
     const FlyString& local_name() const { return m_local_name; }
     const FlyString& prefix() const { return m_prefix; }
     const FlyString& namespace_() const { return m_namespace; }
 
+    const String& as_string() const { return m_as_string; }
+
 private:
     FlyString m_local_name;
     FlyString m_prefix;
     FlyString m_namespace;
+    String m_as_string;
+
+    // https://dom.spec.whatwg.org/#concept-attribute-qualified-name
+    // https://dom.spec.whatwg.org/#concept-element-qualified-name
+    void make_internal_string()
+    {
+        // This is possible to do according to the spec: "User agents could have this as an internal slot as an optimization."
+        if (m_prefix.is_null()) {
+            m_as_string = m_local_name;
+            return;
+        }
+
+        m_as_string = String::formatted("{}:{}", m_prefix, m_local_name);
+    }
 };
 
 }