It is not customizable but you can skip 10% by holding down Ctrl along with the left/right arrow keys.

Video player keyboard shortcuts.

You can make feature requests at connect.mozilla.org.

Hmm, gotcha. Side question, when i do ctrl+left, it sends me back to the start of the video? Any idea why? Cant think of any extension that does that.

It will start from the beginning if the current playback position is within 10% from the start or if you press and hold the key combo. A custom video player may behave differently, try testing with Picture-in-Picture (Ctrl+Shift+]).

well, i wasnt within 10%.. I also dont use a custom player, whatever that means.

I asked the all-knowing oracle of chatgpt and it said this is standard behavior and the seek 10% is a firefox control scheme, which leads me to believe its not working. Why would that be. Is there something i need to enable in about:config maybe. On chrome, ctrl+left is doing like a 1 or 2s seek, which is what im looking for.

Ctrl+left/right seeks 10% for me in the vanilla html5 player and Picture-in-Picture player on Ubuntu. Can you share a video link that does not behave this way?