documentation/content/en/development/activitypub.md

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---
title: ActivityPub compliance
description: What objects and properties of the ActivityPub spec Mastodon supports
menu:
docs:
parent: administration
weight: 5
---
## APIs
- Mastodon supports the server-to-server part of the ActivityPub spec.
- It implements the HTTP signatures spec for authentication of inbox deliveries.
- Mastodon also supports Linked Data Signatures for forwarded payloads.
## Restrictions
- Mastodon requires all object IDs to use the HTTPS schema.
- Mastodon also requires servers to offer a WebFinger endpoint for converting username/domain pairs into actors.
- Mastodon accepts `Application`, `Group`, `Organization`, `Person`, and `Service` as valid types for actors.
- Mastodon requires activities attributed to an actor to have an ID on the same host as the actor.
## Activities
|Supported activity|Supported objects|Notes|
|------------------|-----------------|-----|
|`Accept`|`Follow`|The `object` of the `Follow` is expected to be an actor from the receiving server|
|`Add`|`Note`|Only the actor's own objects and only to the actor's featured collection URI as `target`|
|`Announce`|`Object`|Any object supported by `Create` is supported here|
|`Block`|`Object`|The `object` is expected to point to an actor from the receiving server|
|`Create`|`Note`, `Article`, `Image`, `Video`||
|`Delete`|`Object`|Only the actor's own objects will be deleted, such as anything created before
|`Flag`|`Object`|The `object` is expected to point to one or multiple objects originating on the receiving server|
|`Follow`|`Object`|The `object` is expected to point to an actor from the receiving server|
|`Like`|`Object`|The `object` is expected to be something created on the receiving server|
|`Move`|`Object`|Only the actor's own actor object can be moved to another actor object at `target`|
|`Reject`|`Follow`|The `object` of the `Follow` is expected to be an actor from the receiving server|
|`Remove`|`Note`|Only the actor's own objects and only from the actor's featured collection URI as `origin`|
|`Undo`|`Accept`, `Announce`, `Block`, `Follow`, `Like`||
|`Update`|`Object`|Only the actor's own actor object can be updated|
## Extensions
### Featured collection
What is known in Mastodon as "pinned toots", or statuses that are always featured at the top of people's profiles, is implemented using an extra property `featured` on the actor object that points to a `Collection` of objects. Example:
```json
{
"@context": [
"https://www.w3.org/ns/activitystreams",
{
"toot": "http://joinmastodon.org/ns#",
"featured": {
"@id": "toot:featured",
"@type": "@id"
}
}
],
"id": "https://example.com/@alice",
"type": "Person",
"featured": "https://example.com/@alice/collections/featured"
}
```
### Custom emojis
Mastodon supports arbitrary emojis, that is, small images uploaded by admins and invokable via shortcodes. For this, an `Emoji` type is used. These emojis are listed in the `tag` property just like `Mention` and `Hashtag` objects, since they are entities that affect how the text is rendered. Example:
```json
{
"@context": [
"https://www.w3.org/ns/activitystreams",
{
"toot": "http://joinmastodon.org/ns#",
"Emoji": "toot:Emoji"
}
],
"id": "https://example.com/@alice/hello-world",
"type": "Note",
"content": "Hello world :Kappa:",
"tag": [
{
"id": "https://example.com/emoji/123",
"type": "Emoji",
"name": ":Kappa:",
"icon": {
"type": "Image",
"mediaType": "image/png",
"url": "https://example.com/files/kappa.png"
}
}
]
}
```
### Focal points
Mastodon supports setting a focal point on uploaded images, so that wherever that image is displayed, the focal point stays in view. This is implemented using an extra property `focalPoint` on the `Image` objects. The property is simply an array of two floating points between 0 and 1. Example: