Created attachment 388256 [details] Test case demonstrating behavior This occurs for me building WinCairo port, webkit trunk (revision 254831), but has been the case for quite some time (year+ as it presents in QtWebKit 5.212). Attaching a Javascript callback to the ended event of a video tag and letting the video play through results in the event never getting called. A test case is attach that plays a 15 second video and writes "Fired" to console.log() on ended. Opening the inspector, going to the console, and playing the video never results in the "Fired" message. I made an attempt to patch it that gets the event to fire, but somehow breaks the duration calculation. I've attached it in case it helps narrow down where to start looking for the problem.