YT Preview Media Key Blocker by fftrap

Have you ever been listening to music in Spotify or Apple Music, then hovered over a YouTube video — and suddenly your keyboard's play/pause button stopped working for your music?

That happens because YouTube quietly takes control of your media keys the moment a video preview starts playing, even if you never actually opened that video. The only way to get your keys back is to close the YouTube tab completely, or turn off video previews entirely.

This extension fixes that. When you're just browsing YouTube — hovering over thumbnails, scrolling through results — your media keys stay with whatever app or tab was using them before. Open Spotify, keep browsing YouTube, and your keyboard controls will keep working for Spotify as expected.

Note: if you actually open a video in its own tab, your media keys will control that video as normal. The extension only prevents YouTube from grabbing them in the background while you're just browsing.

No settings, no permissions, nothing to configure — install and it works.
Currently tested on Firefox 150.0.3 (MacBook M1).