YouTube error · Common
YouTube fullscreen not working — fix the F-key and player button
You click the fullscreen button or hit F and nothing happens — the video stays in its embedded box. Different from playback errors; the video is working, the chrome (player UI) isn't.
Why this happens
- Browser extension blocking the Fullscreen API.
- Chrome / Firefox extension permission for Fullscreen denied for this site.
- PiP (Picture-in-Picture) mode was active and is still locking the player.
- Display has fullscreen apps already in foreground (macOS Mission Control / Windows multi-monitor edge case).
- YouTube's player UI bugs that resolve on hard reload.
How to fix it
- 1
Press F or click the fullscreen icon in the player
The F keyboard shortcut works even when the player button visually fails. Make sure the video has focus (click it once first).
- 2
Exit Picture-in-Picture if it's active
PiP keeps the video docked in a corner and blocks fullscreen. Right-click the small PiP video → "Exit Picture-in-Picture".
- 3
Disable browser extensions in incognito
Test the same page in incognito mode with extensions disabled. If fullscreen works there, an extension is blocking it.
- 4
Check Site Settings for Fullscreen permission
Chrome → lock icon next to URL → Site settings → "Fullscreen" → Allow. Some users have inadvertently set this to "Block".
- 5
Hard reload the page
Cmd+Shift+R or Ctrl+F5. Clears stale player JS that may have lost track of the fullscreen state.