WebCodecs
Low-level API for video/audio encoding and decoding in the browser — direct access to hardware codecs without going through <video>.
Classes: VideoEncoder, VideoDecoder, AudioEncoder, AudioDecoder plus VideoFrame/AudioData. You feed in raw frames, get out compressed chunks (or vice versa). Pairs with WebTransport and WebRTC for custom realtime pipelines.
Used by Zoom Web, Discord, cloud-gaming services and anyone who wants lower latency than WebRTC and finer control than MSE. Stable in Chrome/Edge since 2021, Safari 16.4+, Firefox since 2024.