You can hook your MIDI keyboard up to a website with Firefox 108
Can anyone explain to me, what's cool on web midi? I me for me it's totally useless. 
I have a lot of sequencer, synth and midi help plugins in the DAW ... what does a JS interface to the web offers other than the next 100th "I just wrote a little useless javascript music script"-show HN posts?
For me it doesn't solve any problem or satisfy any need. It's just another other thing almost nobody uses in the browser.