I thought it used to be done manually, but now there’s automation built in to YouTube, I recall hearing. It might only be available to certain users, though.

I think I recall it being discussed in relation to Veritasium, although I can’t recall if it was a third party mentioning it or Derek (Veritasium) himself.

I haven’t heard of it built into news websites before, but it also wouldn’t surprise me if that already was a thing.