Thanks to advances in modern technology, you no longer have to open up Firefox and copy request headers from the developer toolbar in order to log into YTMusic Deleter (the app that lets you delete your YouTube Music library). Now you just click a link, log in with your Google account, click another button or two, and you're done! What are you going to do with all this extra time I'm saving you?
Of course, I can't claim full credit for this technological marvel. As you may already know (because I try to say it as often as I can on GitHub) that YTMusic Deleter is built upon an unofficial API for YouTube Music entitled ytmusicapi. The author of that API implemented a OAuth 2.0 login workflow last year, and so when I updated my YTMusic Deleter to use the latest version of ytmusicapi, I got that functionality for free and I just had to hook it up to my application to make it work. Hooray for the open-source community!
Download the 1.6.0 (or later) version of YTMusic Deleter to install or upgrade your existing installation and hit the Log In button to use the easy new login process. Or don't, you know. I mean, if you've already deleted your library, what are the chances that you need to do it again? Do people use this app more than once? (Do people use it at all? Seems like at least a few people do.)
Oh also there's additional changes like a Delete History button that will delete your play history so that Taylor Swift doesn't keep showing up on your recommendations because your girlfriend wanted to play her new album in your car that one time on the way to Panda Express. When you use Delete All, that Delete History function will get invoked now as well.
Happy deleting!