Firefox now (starting with v.96) supports AV1 VA-API playback
Firefox now (starting with v.96) supports AV1 VA-API playback
bugzilla.mozilla.org
1745225 - [Linux] Provide AV1 VA-API playback
RESOLVED (stransky) in Core - Audio/Video: Playback. Last updated 2022-01-21.
tl;dr AV1 is a new video encoding format which now has hardware acceleration through VA-API on Linux