Image Description

The Image type is defined in ActivityStreams Vocabulary.

In this support table, we only consider how the image description, commonly called AltText is handled. Image descriptions are important from an accessibility standpoint, see WCAG 2.2. Text Alternatives.

It seems that certain implementations, e.g. firefish, store the image description on a per image URL basis and not for every instance of an image reference.

Examples

Example 1

activity

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://hollo/@john"
  ],
  "id": "http://pasture-one-actor/actor/okkWSMphs-E",
  "published": "2024-12-02T09:44:11Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://hollo/@john"
    ],
    "id": "http://pasture-one-actor/actor/F0BbfyVbyik",
    "published": "2024-12-02T09:44:11Z",
    "content": "no description",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png"
    },
    "tag": [
      {
        "type": "Mention",
        "href": "http://gotosocial/users/cookie"
      }
    ]
  }
}

hollo

{
  "id": "019386c1-89f8-7127-adca-9c1c14f012fd",
  "created_at": "2024-12-02T09:44:11.000Z",
  "in_reply_to_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/F0BbfyVbyik",
  "url": "http://pasture-one-actor/actor/F0BbfyVbyik",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "pinned": false,
  "content": "no description",
  "reblog": null,
  "quote_id": null,
  "quote": null,
  "application": null,
  "account": {
    "id": "019386c0-d3fa-7b3c-baaa-560ebae8a25c",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "created_at": "2024-12-02T09:43:24.319Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://hollo/image/avatars/original/missing.png",
    "avatar_static": "http://hollo/image/avatars/original/missing.png",
    "header": "http://hollo/image/headers/original/missing.png",
    "header_static": "http://hollo/image/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 0,
    "moved": null,
    "last_status_at": null,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "019386c1-8e25-7bb9-9c4a-8173968248eb",
      "type": "image",
      "url": "http://pasture-one-actor/images/100.png",
      "preview_url": "http://pasture-one-actor/images/100.png",
      "remote_url": null,
      "text_url": null,
      "meta": {
        "original": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "small": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "focus": {
          "x": 0,
          "y": 0
        }
      },
      "description": null,
      "blurhash": null
    }
  ],
  "mentions": [],
  "tags": [],
  "card": null,
  "emojis": [],
  "emoji_reactions": [],
  "poll": null,
  "filtered": null
}

Example 2

activity

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://hollo/@john"
  ],
  "id": "http://pasture-one-actor/actor/HrUiUM-8k5o",
  "published": "2024-12-02T09:44:12Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://hollo/@john"
    ],
    "id": "http://pasture-one-actor/actor/C11CKwR45p4",
    "published": "2024-12-02T09:44:12Z",
    "content": "text",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png",
      "name": "name",
      "summary": "summary",
      "content": "content"
    },
    "tag": [
      {
        "type": "Mention",
        "href": "http://gotosocial/users/cookie"
      }
    ]
  }
}

hollo

{
  "id": "019386c1-8de0-7f04-8196-35b706b8e89b",
  "created_at": "2024-12-02T09:44:12.000Z",
  "in_reply_to_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/C11CKwR45p4",
  "url": "http://pasture-one-actor/actor/C11CKwR45p4",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "pinned": false,
  "content": "text",
  "reblog": null,
  "quote_id": null,
  "quote": null,
  "application": null,
  "account": {
    "id": "019386c0-d3fa-7b3c-baaa-560ebae8a25c",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "created_at": "2024-12-02T09:43:24.319Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://hollo/image/avatars/original/missing.png",
    "avatar_static": "http://hollo/image/avatars/original/missing.png",
    "header": "http://hollo/image/headers/original/missing.png",
    "header_static": "http://hollo/image/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 0,
    "moved": null,
    "last_status_at": null,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "019386c1-9125-71b7-ba66-5ddfa5fc6583",
      "type": "image",
      "url": "http://pasture-one-actor/images/100.png",
      "preview_url": "http://pasture-one-actor/images/100.png",
      "remote_url": null,
      "text_url": null,
      "meta": {
        "original": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "small": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "focus": {
          "x": 0,
          "y": 0
        }
      },
      "description": "summary",
      "blurhash": null
    }
  ],
  "mentions": [],
  "tags": [],
  "card": null,
  "emojis": [],
  "emoji_reactions": [],
  "poll": null,
  "filtered": null
}

Example 3

activity

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://hollo/@john"
  ],
  "id": "http://pasture-one-actor/actor/vlN1iISdLRk",
  "published": "2024-12-02T09:44:13Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://hollo/@john"
    ],
    "id": "http://pasture-one-actor/actor/pOyzG9QB2B8",
    "published": "2024-12-02T09:44:13Z",
    "content": "text",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png",
        "name": "name",
        "imageType": "image/jpeg"
      }
    ],
    "tag": [
      {
        "type": "Mention",
        "href": "http://gotosocial/users/cookie"
      }
    ]
  }
}

hollo

{
  "id": "019386c1-91c8-7dda-860c-08cb26eac430",
  "created_at": "2024-12-02T09:44:13.000Z",
  "in_reply_to_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/pOyzG9QB2B8",
  "url": "http://pasture-one-actor/actor/pOyzG9QB2B8",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "pinned": false,
  "content": "text",
  "reblog": null,
  "quote_id": null,
  "quote": null,
  "application": null,
  "account": {
    "id": "019386c0-d3fa-7b3c-baaa-560ebae8a25c",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "created_at": "2024-12-02T09:43:24.319Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://hollo/image/avatars/original/missing.png",
    "avatar_static": "http://hollo/image/avatars/original/missing.png",
    "header": "http://hollo/image/headers/original/missing.png",
    "header_static": "http://hollo/image/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 0,
    "moved": null,
    "last_status_at": null,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "019386c1-9468-72c8-b4c6-dfd363ef6126",
      "type": "image",
      "url": "http://pasture-one-actor/assets/FediverseLogo.png",
      "preview_url": "http://pasture-one-actor/assets/FediverseLogo.png",
      "remote_url": null,
      "text_url": null,
      "meta": {
        "original": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "small": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "focus": {
          "x": 0,
          "y": 0
        }
      },
      "description": "name",
      "blurhash": null
    }
  ],
  "mentions": [],
  "tags": [],
  "card": null,
  "emojis": [],
  "emoji_reactions": [],
  "poll": null,
  "filtered": null
}

Example 4

activity

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://hollo/@john"
  ],
  "id": "http://pasture-one-actor/actor/WPQum2SSusg",
  "published": "2024-12-02T09:44:14Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://hollo/@john"
    ],
    "id": "http://pasture-one-actor/actor/8gEJ9xhePVM",
    "published": "2024-12-02T09:44:14Z",
    "content": "no comment in attachment",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png"
      }
    ],
    "tag": [
      {
        "type": "Mention",
        "href": "http://gotosocial/users/cookie"
      }
    ]
  }
}

hollo

{
  "id": "019386c1-95b0-7e31-b6d7-7db59252d6b0",
  "created_at": "2024-12-02T09:44:14.000Z",
  "in_reply_to_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/8gEJ9xhePVM",
  "url": "http://pasture-one-actor/actor/8gEJ9xhePVM",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "pinned": false,
  "content": "no comment in attachment",
  "reblog": null,
  "quote_id": null,
  "quote": null,
  "application": null,
  "account": {
    "id": "019386c0-d3fa-7b3c-baaa-560ebae8a25c",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "created_at": "2024-12-02T09:43:24.319Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://hollo/image/avatars/original/missing.png",
    "avatar_static": "http://hollo/image/avatars/original/missing.png",
    "header": "http://hollo/image/headers/original/missing.png",
    "header_static": "http://hollo/image/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 0,
    "moved": null,
    "last_status_at": null,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "019386c1-97a9-77d8-9b90-7ac981389d23",
      "type": "image",
      "url": "http://pasture-one-actor/assets/FediverseLogo.png",
      "preview_url": "http://pasture-one-actor/assets/FediverseLogo.png",
      "remote_url": null,
      "text_url": null,
      "meta": {
        "original": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "small": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "focus": {
          "x": 0,
          "y": 0
        }
      },
      "description": null,
      "blurhash": null
    }
  ],
  "mentions": [],
  "tags": [],
  "card": null,
  "emojis": [],
  "emoji_reactions": [],
  "poll": null,
  "filtered": null
}