I found this a very helpful discussion of IndieAuth from Desmond, touching on web sign-in, RelMeAuth, OAuth and OIDC along the way. It’s one of those things that I know exists, and just works for me (e.g. everytime I use a Micropub client), but it’s nice to get a bit of a handle on how it works.

In a nutshell the purpose is this:

your domain should function as a kind of universal online passport, allowing you to sign in to various services and applications simply by entering your personal URL

Desmond does a great job of explaining the nitty-gritty of how it works, too. The two bits I bolded below jumped out at me – a decentralised authentication mechanism leveraging DNS as a user registration system. It’s very elegant.

The process of using your domain to log in to sites and services is called web sign-in and is implemented via a protocol called IndieAuth, an extension of OAuth used for decentralized authentication.

If your goal is to make a social network out of the world wide web, there is a certain elegance to the idea of leveraging DNS as a user registration system.