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/7XyeOARaCNA",
  "published": "2024-12-20T15:26:24Z",
  "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/JsJOvjBNA7s",
    "published": "2024-12-20T15:26:24Z",
    "content": "no description",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png"
    },
    "tag": [
      {
        "type": "Mention",
        "href": "http://gotosocial/users/cookie"
      }
    ]
  }
}

hollo

{
  "id": "0193e4ad-5100-789d-ae8c-c0dae9798ff0",
  "created_at": "2024-12-20T15:26:24.000Z",
  "in_reply_to_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/JsJOvjBNA7s",
  "url": "http://pasture-one-actor/actor/JsJOvjBNA7s",
  "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": "0193e4ac-8732-721f-9770-fa83add95811",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "created_at": "2024-12-20T15:25:32.251Z",
    "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": "0193e4ad-52ea-7eb6-893d-e0853c510644",
      "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/tf5YzKvAl9g",
  "published": "2024-12-20T15:26:25Z",
  "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/0w6GRhCB-gs",
    "published": "2024-12-20T15:26:25Z",
    "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": "0193e4ad-54e8-7161-a016-83bef2c20b69",
  "created_at": "2024-12-20T15:26:25.000Z",
  "in_reply_to_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/0w6GRhCB-gs",
  "url": "http://pasture-one-actor/actor/0w6GRhCB-gs",
  "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": "0193e4ac-8732-721f-9770-fa83add95811",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "created_at": "2024-12-20T15:25:32.251Z",
    "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": "0193e4ad-5624-7e1b-8d87-c214165e3e52",
      "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/RAZDp93246U",
  "published": "2024-12-20T15:26:25Z",
  "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/nG2PpC4nUOo",
    "published": "2024-12-20T15:26:25Z",
    "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": "0193e4ad-54e8-7161-a016-83bf6faf218c",
  "created_at": "2024-12-20T15:26:25.000Z",
  "in_reply_to_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/nG2PpC4nUOo",
  "url": "http://pasture-one-actor/actor/nG2PpC4nUOo",
  "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": "0193e4ac-8732-721f-9770-fa83add95811",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "created_at": "2024-12-20T15:25:32.251Z",
    "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": "0193e4ad-5949-744d-b548-df8421b0e2a1",
      "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/Hug7GSqanUE",
  "published": "2024-12-20T15:26:27Z",
  "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/qfQ6yQpV4T4",
    "published": "2024-12-20T15:26:27Z",
    "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": "0193e4ad-5cb8-7c54-9409-0d002b1dc24f",
  "created_at": "2024-12-20T15:26:27.000Z",
  "in_reply_to_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/qfQ6yQpV4T4",
  "url": "http://pasture-one-actor/actor/qfQ6yQpV4T4",
  "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": "0193e4ac-8732-721f-9770-fa83add95811",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "created_at": "2024-12-20T15:25:32.251Z",
    "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": "0193e4ad-5e9a-7f59-9a25-420a9eb4dc7b",
      "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
}