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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": [
    "http://gotosocial/users/cookie",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/U3vtCr8gLyM",
  "published": "2024-12-04T17:58:06Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://gotosocial/users/cookie"
    ],
    "id": "http://pasture-one-actor/actor/K2dej5MEWyw",
    "published": "2024-12-04T17:58:06Z",
    "content": "no description",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png"
    },
    "tag": [
      {
        "type": "Mention",
        "href": "http://gotosocial/users/cookie"
      }
    ]
  }
}
gotosocial
{
  "id": "01JE9D4WXGCW90VEVSEK9HC10B",
  "created_at": "2024-12-04T17:58:06.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/K2dej5MEWyw",
  "url": "http://pasture-one-actor/actor/K2dej5MEWyw",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "pinned": false,
  "content": "no description",
  "reblog": null,
  "account": {
    "id": "01JE9D28EG7DDB9G7JGPT4RQWR",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": true,
    "discoverable": false,
    "bot": false,
    "created_at": "2024-12-04T17:56:39.515Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://gotosocial/assets/default_avatars/GoToSocial_icon2.png",
    "avatar_static": "http://gotosocial/assets/default_avatars/GoToSocial_icon2.png",
    "header": "http://gotosocial/assets/default_header.png",
    "header_static": "http://gotosocial/assets/default_header.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 34,
    "last_status_at": "2024-12-04T17:58:06.000Z",
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "01JE9D4XMBGGAG30HGQ0EYNR2K",
      "type": "image",
      "url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/original/01JE9D4XMBGGAG30HGQ0EYNR2K.png",
      "text_url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/original/01JE9D4XMBGGAG30HGQ0EYNR2K.png",
      "preview_url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/small/01JE9D4XMBGGAG30HGQ0EYNR2K.jpg",
      "remote_url": "http://pasture-one-actor/images/100.png",
      "preview_remote_url": null,
      "meta": {
        "original": {
          "width": 40,
          "height": 40,
          "size": "40x40",
          "aspect": 1
        },
        "small": {
          "width": 40,
          "height": 40,
          "size": "40x40",
          "aspect": 1
        },
        "focus": {
          "x": 0,
          "y": 0
        }
      },
      "description": null,
      "blurhash": "L6O3Eu~TfQ~T~ToLfQoLfQfQfQfQ"
    }
  ],
  "mentions": [
    {
      "id": "01GDD6QXCF4BJZT90ZTC9GXNJG",
      "username": "cookie",
      "url": "http://gotosocial/@cookie",
      "acct": "cookie"
    }
  ],
  "tags": [],
  "emojis": [],
  "card": null,
  "poll": 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": [
    "http://gotosocial/users/cookie",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/dCcwcpwC7O8",
  "published": "2024-12-04T17:58:07Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://gotosocial/users/cookie"
    ],
    "id": "http://pasture-one-actor/actor/xjLj_Pr7UBI",
    "published": "2024-12-04T17:58:07Z",
    "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"
      }
    ]
  }
}
gotosocial
{
  "id": "01JE9D4XWRV0Q5MWF6AMCJM0P8",
  "created_at": "2024-12-04T17:58:07.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/xjLj_Pr7UBI",
  "url": "http://pasture-one-actor/actor/xjLj_Pr7UBI",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "pinned": false,
  "content": "text",
  "reblog": null,
  "account": {
    "id": "01JE9D28EG7DDB9G7JGPT4RQWR",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": true,
    "discoverable": false,
    "bot": false,
    "created_at": "2024-12-04T17:56:39.515Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://gotosocial/assets/default_avatars/GoToSocial_icon2.png",
    "avatar_static": "http://gotosocial/assets/default_avatars/GoToSocial_icon2.png",
    "header": "http://gotosocial/assets/default_header.png",
    "header_static": "http://gotosocial/assets/default_header.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 35,
    "last_status_at": "2024-12-04T17:58:07.000Z",
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "01JE9D4Y8PEDXXGRAEW1G3Z6J3",
      "type": "image",
      "url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/original/01JE9D4Y8PEDXXGRAEW1G3Z6J3.png",
      "text_url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/original/01JE9D4Y8PEDXXGRAEW1G3Z6J3.png",
      "preview_url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/small/01JE9D4Y8PEDXXGRAEW1G3Z6J3.jpg",
      "remote_url": "http://pasture-one-actor/images/100.png",
      "preview_remote_url": null,
      "meta": {
        "original": {
          "width": 40,
          "height": 40,
          "size": "40x40",
          "aspect": 1
        },
        "small": {
          "width": 40,
          "height": 40,
          "size": "40x40",
          "aspect": 1
        },
        "focus": {
          "x": 0,
          "y": 0
        }
      },
      "description": "summary",
      "blurhash": "L2F?Xu_MfQ_M_MkBfQkBfQfQfQfQ"
    }
  ],
  "mentions": [
    {
      "id": "01GDD6QXCF4BJZT90ZTC9GXNJG",
      "username": "cookie",
      "url": "http://gotosocial/@cookie",
      "acct": "cookie"
    }
  ],
  "tags": [],
  "emojis": [],
  "card": null,
  "poll": 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": [
    "http://gotosocial/users/cookie",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/SzlKxzPLNTY",
  "published": "2024-12-04T17:58:07Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://gotosocial/users/cookie"
    ],
    "id": "http://pasture-one-actor/actor/jg9y7fpjOCo",
    "published": "2024-12-04T17:58:07Z",
    "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"
      }
    ]
  }
}
gotosocial
{
  "id": "01JE9D4XWRC80W5SX8DCG0BPWR",
  "created_at": "2024-12-04T17:58:07.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/jg9y7fpjOCo",
  "url": "http://pasture-one-actor/actor/jg9y7fpjOCo",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "pinned": false,
  "content": "text",
  "reblog": null,
  "account": {
    "id": "01JE9D28EG7DDB9G7JGPT4RQWR",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": true,
    "discoverable": false,
    "bot": false,
    "created_at": "2024-12-04T17:56:39.515Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://gotosocial/assets/default_avatars/GoToSocial_icon2.png",
    "avatar_static": "http://gotosocial/assets/default_avatars/GoToSocial_icon2.png",
    "header": "http://gotosocial/assets/default_header.png",
    "header_static": "http://gotosocial/assets/default_header.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 36,
    "last_status_at": "2024-12-04T17:58:07.000Z",
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "01JE9D4YXXV817F6PHS5DDT5CP",
      "type": "image",
      "url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/original/01JE9D4YXXV817F6PHS5DDT5CP.png",
      "text_url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/original/01JE9D4YXXV817F6PHS5DDT5CP.png",
      "preview_url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/small/01JE9D4YXXV817F6PHS5DDT5CP.jpg",
      "remote_url": "http://pasture-one-actor/assets/FediverseLogo.png",
      "preview_remote_url": null,
      "meta": {
        "original": {
          "width": 1548,
          "height": 1548,
          "size": "1548x1548",
          "aspect": 1
        },
        "small": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "focus": {
          "x": 0,
          "y": 0
        }
      },
      "description": "name",
      "blurhash": "LIB{x~.}9Fcn}gnOEUxBDlK[N1wi"
    }
  ],
  "mentions": [
    {
      "id": "01GDD6QXCF4BJZT90ZTC9GXNJG",
      "username": "cookie",
      "url": "http://gotosocial/@cookie",
      "acct": "cookie"
    }
  ],
  "tags": [],
  "emojis": [],
  "card": null,
  "poll": 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": [
    "http://gotosocial/users/cookie",
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "id": "http://pasture-one-actor/actor/bzKbXPHq4C0",
  "published": "2024-12-04T17:58:08Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://gotosocial/users/cookie"
    ],
    "id": "http://pasture-one-actor/actor/zDT_z46acCM",
    "published": "2024-12-04T17:58:08Z",
    "content": "no comment in attachment",
    "attachment": [
      {
        "type": "Document",
        "url": "http://pasture-one-actor/assets/FediverseLogo.png"
      }
    ],
    "tag": [
      {
        "type": "Mention",
        "href": "http://gotosocial/users/cookie"
      }
    ]
  }
}
gotosocial
{
  "id": "01JE9D4YW0QPBZ23Y16FA4KZ6F",
  "created_at": "2024-12-04T17:58:08.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/actor/zDT_z46acCM",
  "url": "http://pasture-one-actor/actor/zDT_z46acCM",
  "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,
  "account": {
    "id": "01JE9D28EG7DDB9G7JGPT4RQWR",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": true,
    "discoverable": false,
    "bot": false,
    "created_at": "2024-12-04T17:56:39.515Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://gotosocial/assets/default_avatars/GoToSocial_icon2.png",
    "avatar_static": "http://gotosocial/assets/default_avatars/GoToSocial_icon2.png",
    "header": "http://gotosocial/assets/default_header.png",
    "header_static": "http://gotosocial/assets/default_header.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 37,
    "last_status_at": "2024-12-04T17:58:08.000Z",
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "01JE9D4ZKPGXTBXNNNWECV6YVY",
      "type": "image",
      "url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/original/01JE9D4ZKPGXTBXNNNWECV6YVY.png",
      "text_url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/original/01JE9D4ZKPGXTBXNNNWECV6YVY.png",
      "preview_url": "http://gotosocial/fileserver/01JE9D28EG7DDB9G7JGPT4RQWR/attachment/small/01JE9D4ZKPGXTBXNNNWECV6YVY.jpg",
      "remote_url": "http://pasture-one-actor/assets/FediverseLogo.png",
      "preview_remote_url": null,
      "meta": {
        "original": {
          "width": 1548,
          "height": 1548,
          "size": "1548x1548",
          "aspect": 1
        },
        "small": {
          "width": 512,
          "height": 512,
          "size": "512x512",
          "aspect": 1
        },
        "focus": {
          "x": 0,
          "y": 0
        }
      },
      "description": null,
      "blurhash": "LIB{x~.}9Fcn}gnOEUxBDlK[N1wi"
    }
  ],
  "mentions": [
    {
      "id": "01GDD6QXCF4BJZT90ZTC9GXNJG",
      "username": "cookie",
      "url": "http://gotosocial/@cookie",
      "acct": "cookie"
    }
  ],
  "tags": [],
  "emojis": [],
  "card": null,
  "poll": null
}