The spec is: https://dom.spec.whatwg.org/#dom-event-composedpath The relevant change of the spec: https://github.com/whatwg/dom/pull/327 Before: event.composedPath() on window object returns [window] in Blink, which does not include nodes in a document. After: event.composedPath() on window behaves the same way as that on document. It would include a node in a document tree.