Follow

Mastodon sends a Follow activity when an actor follows an external actor. It also accepts Follow activities send by external instances when one of their actors follows a Mastodon actor.

When the receiving actor accepts the follow, its instance is generally expected to send an Accept in response. Mastodon will not deliver an actor’s activities to a new follower until that follower has accepted the follow.

Mastodon’s Follow activity ids aren’t fetchable via HTTP with Accept: application/activity+json content negotiation; they return HTTP 404 {"error":"Not Found"}.

Request

Example Follow request

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "id": "https://example.com/fce205fc-fced-4d81-9a7d-5485eec038a3",
  "type": "Follow",
  "actor": "https://example.com/users/123",
  "object": "https://other.example/users/456"
}

Accept

The Accept activity is used to accept another activity that was previously received, usually a Follow.

Mastodon’s Accept activity ids are based on their actor’s ids, distinguished with a # fragment, which makes them not fetchable via HTTP with Accept: application/activity+json content negotiation. Attempting to fetch them returns the actor’s AS2 object instead. Background in this GitHub issue.

Example Accept request

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "id": "https://other.example/users/456#accepts/follows/283636",
  "type": "Accept",
  "actor": "https://other.example/users/456",
  "object": {
    "id": "https://example.com/fce205fc-fced-4d81-9a7d-5485eec038a3",
    "type": "Follow",
    "actor": "https://example.com/users/123",
    "object": "https://other.example/users/456"
  }
}