As part of the Fenced Storage Read API, fenced frame documents will have access to a new function called window.fence.notifyEvent(). When called with a user-generated click event, this function will fire a fencedtreeclick event in the embedding document, allowing the embedder to listen for a click inside of the fenced frame. Note that fencedtreeclick events do not contain position or timing information, and just signal that a click has occurred.

This function will be available in all types of fenced frames, including those initialized from Protected Audience auctions and sharedStorage.selectURL(). However, Fenced Frames Ad Reporting (FFAR) should still be used for reporting clicks on ads. Use window.fence.notifyEvent() only to report the presence of a click to the embedding document, and embedders should prefer this API over placing an overlay on the frame.