Object Types Reference

This reference covers all standard ActivityStreams object types used in the Fediverse.

Core Object Types

Note

Short-form text content (the most common type):

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Note",
  "id": "https://example.com/notes/1",
  "attributedTo": "https://example.com/users/alice",
  "content": "<p>Hello, Fediverse!</p>",
  "published": "2024-01-15T10:30:00Z",
  "to": ["https://www.w3.org/ns/activitystreams#Public"],
  "cc": ["https://example.com/users/alice/followers"],
  "sensitive": false,
  "tag": [],
  "attachment": [],
  "inReplyTo": null
}

Property	Type	Description
content	String (HTML)	The post content
published	DateTime	When created
inReplyTo	URL	Parent post (for replies)
sensitive	Boolean	Content warning flag
summary	String	Content warning text
tag	Array	Mentions, hashtags, emoji
attachment	Array	Media attachments

Article

Long-form content with a title:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Article",
  "id": "https://blog.example/articles/1",
  "attributedTo": "https://blog.example/users/writer",
  "name": "Understanding ActivityPub",
  "content": "<p>ActivityPub is a protocol...</p>",
  "summary": "An introduction to federated social networking",
  "published": "2024-01-15T10:30:00Z",
  "url": "https://blog.example/posts/understanding-activitypub"
}

Key difference from Note: Article has a name (title).

Image

Photo/image content:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Image",
  "id": "https://pixelfed.example/p/1",
  "attributedTo": "https://pixelfed.example/users/photographer",
  "name": "Sunset at the beach",
  "url": {
    "type": "Link",
    "href": "https://pixelfed.example/storage/1.jpg",
    "mediaType": "image/jpeg",
    "width": 1920,
    "height": 1080
  }
}

Video

Video content:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Video",
  "id": "https://peertube.example/videos/1",
  "attributedTo": "https://peertube.example/accounts/creator",
  "name": "My Video",
  "duration": "PT15M30S",
  "url": [
    {
      "type": "Link",
      "href": "https://peertube.example/videos/1.mp4",
      "mediaType": "video/mp4",
      "height": 1080
    }
  ]
}

Audio

Audio content:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Audio",
  "id": "https://funkwhale.example/tracks/1",
  "attributedTo": "https://funkwhale.example/users/musician",
  "name": "My Song",
  "duration": "PT3M45S",
  "url": {
    "type": "Link",
    "href": "https://funkwhale.example/tracks/1.mp3",
    "mediaType": "audio/mpeg"
  }
}

Document

Generic file/attachment:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Document",
  "mediaType": "image/png",
  "url": "https://example.com/files/image.png",
  "name": "Screenshot",
  "blurhash": "LEHV6nWB2yk8pyo0adR*.7kCMdnj",
  "width": 1920,
  "height": 1080
}

Used primarily for attachments in Notes.

Page

Link/URL sharing (used by Lemmy):

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Page",
  "id": "https://lemmy.example/post/1",
  "attributedTo": "https://lemmy.example/u/alice",
  "name": "Interesting Article",
  "content": "My commentary on this article...",
  "url": "https://example.com/article"
}

Event

Calendar events:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Event",
  "id": "https://events.example/events/1",
  "name": "Developer Meetup",
  "content": "Join us for a discussion about ActivityPub",
  "startTime": "2024-02-15T18:00:00Z",
  "endTime": "2024-02-15T21:00:00Z",
  "location": {
    "type": "Place",
    "name": "Community Center",
    "address": "123 Main St"
  }
}

Question (Poll)

Polls:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Question",
  "id": "https://example.com/polls/1",
  "attributedTo": "https://example.com/users/alice",
  "content": "What's your favorite language?",
  "endTime": "2024-01-22T10:30:00Z",
  "oneOf": [
    {
      "type": "Note",
      "name": "JavaScript",
      "replies": { "type": "Collection", "totalItems": 42 }
    },
    {
      "type": "Note",
      "name": "Python",
      "replies": { "type": "Collection", "totalItems": 38 }
    }
  ]
}

Use oneOf for single choice, anyOf for multiple choice.

Place

Location information:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Place",
  "name": "Central Park",
  "latitude": 40.785091,
  "longitude": -73.968285,
  "address": "New York, NY"
}

Tombstone

Deleted content:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Tombstone",
  "id": "https://example.com/notes/1",
  "formerType": "Note",
  "deleted": "2024-01-16T12:00:00Z"
}

Fediverse Extensions

Emoji (Custom Emoji)

{
  "type": "Emoji",
  "id": "https://example.com/emoji/awesome",
  "name": ":awesome:",
  "icon": {
    "type": "Image",
    "url": "https://example.com/emoji/awesome.png",
    "mediaType": "image/png"
  }
}

Hashtag

{
  "type": "Hashtag",
  "href": "https://example.com/tags/activitypub",
  "name": "#activitypub"
}

Mention

{
  "type": "Mention",
  "href": "https://example.com/users/bob",
  "name": "@bob@example.com"
}

PropertyValue (Profile Fields)

{
  "type": "PropertyValue",
  "name": "Website",
  "value": "<a href=\"https://example.com\" rel=\"me\">example.com</a>"
}

Type Summary Table

Type	Primary Use	Has Title
Note	Short posts, toots	No
Article	Blog posts	Yes
Image	Photos	Yes
Video	Videos	Yes
Audio	Music, podcasts	Yes
Document	Attachments	Optional
Page	Link shares	Yes
Event	Calendar events	Yes
Question	Polls	No
Place	Locations	Yes
Tombstone	Deleted content	No

See Also

• Activity Types - Actions on objects
• Common Properties - Shared properties
• Posts and Replies - Implementation guide