When building apps with WebCodecs, you need to specify codec strings to configure the encoder/decoder, you need 'avc1.42001f' not just 'avc'.

Nowhere on the internet is there any list of actual valid strings you can use, let alone which strings are supported on which browsers.

So I compiled a dataset of 71M codec string tests, from 220k user sessions, testing 1087 codec strings from an app I manage, built and released the dataset and added codec support tables anyone can reference.