diff --git a/Userland/Libraries/LibWeb/DOM/Node.cpp b/Userland/Libraries/LibWeb/DOM/Node.cpp
index fe1ee4242d..ba003535e3 100644
--- a/Userland/Libraries/LibWeb/DOM/Node.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Node.cpp
@@ -866,4 +866,11 @@ bool Node::is_equal_node(Node const* other_node) const
     return true;
 }
 
+// https://dom.spec.whatwg.org/#in-a-document-tree
+bool Node::in_a_document_tree() const
+{
+    // An element is in a document tree if its root is a document.
+    return root().is_document();
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/DOM/Node.h b/Userland/Libraries/LibWeb/DOM/Node.h
index 77a6051651..ae21a766fd 100644
--- a/Userland/Libraries/LibWeb/DOM/Node.h
+++ b/Userland/Libraries/LibWeb/DOM/Node.h
@@ -71,6 +71,8 @@ public:
     virtual bool requires_svg_container() const { return false; }
     virtual bool is_svg_container() const { return false; }
 
+    bool in_a_document_tree() const;
+
     // NOTE: This is intended for the JS bindings.
     u16 node_type() const { return (u16)m_type; }