Try the h264ify extension, it forces h264 video instead of webm, you can block 60fps videos too if you want to halve the size of the download. If your cpu does

Try the h264ify extension, it forces h264 video instead of webm, you can block 60fps videos too if you want to halve the size of the download. If your cpu does not have a webm decoder in hardware, it has to decode them in software which is inefficient.