In Chrome and Edge you can use WebCodecs to decode and display video frames one-by-one. (this is what I used for the video editor at https://vidmix.app )
In other browsers you could build FFmpeg with webassembly and use that for frame-by-frame decoding but it's not going to be nearly as performant.
In other browsers you could build FFmpeg with webassembly and use that for frame-by-frame decoding but it's not going to be nearly as performant.