webfinger

What's Webfinger?

Webfinger, a protocol for discovering objects on the server. It's used by Mastodon and is important for interop'ing with Mastodon (and most ActivityPub servers).

It lives at a special route: GET /.well-known/webfinger.

We can expect a webfinger response to always looks something like this:

{
  "subject": "acct:[email protected]",

  "links": [
    {
      "rel": "self",
      "type": "application/activity+json",
      "href": "https://my-example.com/actor"
    }
  ]
}

In this case, alice is the ActivityPub Organization slug, and my-example.com is the domain of the server.