There is IndieAuth, which adapts OAuth 2 to work with URLs as identities (and being OAuth, can even do authorization): <a href="https://aaronparecki.com/2018/07/07/7/oauth-for-the-open-web" rel="nofollow">https://aaronparecki.com/2018/07/07/7/oauth-for-the-open-web</a><p><a href="https://indieauth.net/" rel="nofollow">https://indieauth.net/</a>