User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:138.0) Gecko/20100101 Firefox/138.0

Steps to reproduce:

Fireup any youtube videos , twitch videos etc.

Actual results:

When I clicked full screen the Windows Taskbar is still visible. I tried it with freshly installed firefox it still happening. Tried on Chrome it works properly.

Expected results:

Taskbar should've hide when you play full screen videos.

The Bugbug bot thinks this bug should belong to the 'Core::Audio/Video: Playback' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

The severity field is not set for this bug.
:jimm, could you have a look please?

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A regression range would be helpful. We have a tool that helps find these, you can try it out here https://mozilla.github.io/mozregression/.

Not able to reproduce on Windows 11 + Youtube. This might be a regression in changes in widget or maybe DOM fullscreen code, not sure.

Interesting comment from support post. So fullscreen PiP window works as expected, but fullscreen video windows do not. This sounds more like a DOM windowing issue.

I also have this confusion, firefox on 137.0.2 performance is still normal, but upgrade to 138.0~139.0b3 is in the video full screen when the windows10 taskbar can not be hidden correctly.

But if you first enable the video in picture control, and then the full-screen video can hide the taskbar.

Set release status flags based on info from the regressing bug 1950441