I don't even use this addon for the h264 aspect, just the fact that it can block 60fps videos (forcing 30fps) to prevent stuttering. Good job

The developer had the good foresight to listen to Mozilla and update their add-on, before the final release of Firefox 57. As a result, it is completely compatible.

This add-on also makes browsing and streaming videos even faster.

Funciona perfeitamente!!!

I tried testing it on youtubes test page & it never acknowledged h264 so a useless add on it seems.