hi, Using Firefox 104.0.1 on Windows 7 I see two different behaviors from other browsers regarding video playback: 1- the video tag background is displayed in the video element between the poster and the playback (background is shown between the two videos changed the src attribute) 2- event playing not indicates playing video, when the playing event arrives I see the video is not playing and the background of the video tag is shown. Can check this in this example that the red background is shown between the two videos (this behavior is not in chrome): 1. Open this proof-of-concept ( https://jsfiddle.net/wj62hxg8/3/show ), 2. click on "Start" button for play the video, 3. after 2 seconds the src video change and red background is shown. Best regards Fabrizio