This is because Youtube pushes VP8/VP9-encoded video by default to save on bandwidth. Unfortunately, absence of a hardware decoder consumes a ton of battery. Bo

This is because Youtube pushes VP8/VP9-encoded video by default to save on bandwidth. Unfortunately, absence of a hardware decoder consumes a ton of battery. Both Firefox and Chrome receive VP9 encoded video. Safari doesn't understand VP9. So Youtube pushes H.264 video which can be hardware accelerated. To force youtube to send H264 in firefox/chrome you need something like https://addons.mozilla.org/en-US/firefox/addon/h264ify/ https://addons.mozilla.org/en-US/firefox/addon/h264ify/