It seems like it's very specific to YouTube needs. It supports very few HTML elements and CSS properties [1]. If you think HTML5 subset implies something like HTML4 than you're going to be disappointed. It's very much specialised for div-soup-style apps.<p>[1]: <a href="https://developers.google.com/youtube/cobalt/docs/development/reference/supported-features" rel="nofollow">https://developers.google.com/youtube/cobalt/docs/developmen...</a>
A previous thread on Cobalt (22 Nov 2022, 51 comments) - <a href="https://news.ycombinator.com/item?id=33706197">https://news.ycombinator.com/item?id=33706197</a>
Somewhat funny that it has the same name as <a href="https://cobalt.tools" rel="nofollow">https://cobalt.tools</a> which lets you download audio and video from many sources including YouTube.
This looks like a good way to create your own custom combo of software + hardware for a nostalgic TV, like <a href="http://my90stv.com" rel="nofollow">http://my90stv.com</a><p>Put it into a 4:3 CRT tv for maximum authenticity.