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. misskey, 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://gotosocial/users/cookie"
  ],
  "id": "http://pasture-one-actor/activity/kTN9jTTwOkM",
  "published": "2025-09-03T18:25:51Z",
  "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/object/3IwWeWzeZSA",
    "published": "2025-09-03T18:25:51Z",
    "content": "no description",
    "attachment": {
      "type": "Document",
      "url": "http://pasture-one-actor/images/100.png"
    },
    "tag": [
      {
        "type": "Mention",
        "href": "http://gotosocial/users/cookie"
      }
    ]
  }
}

gotosocial

{
  "id": "01K48D7XWRSQHWHQA2V8HMTSNS",
  "created_at": "2025-09-03T18:25:51.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/3IwWeWzeZSA",
  "url": "http://pasture-one-actor/object/3IwWeWzeZSA",
  "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": "01K48D4GXYW9KT1VG7A7FX4SYD",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": true,
    "discoverable": false,
    "bot": false,
    "created_at": "2025-09-03T18:23:59.442Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://gotosocial/assets/default_avatars/GoToSocial_icon4.png",
    "avatar_static": "http://gotosocial/assets/default_avatars/GoToSocial_icon4.png",
    "header": "http://gotosocial/assets/default_header.png",
    "header_static": "http://gotosocial/assets/default_header.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 73,
    "last_status_at": "2025-09-03T18:25:51.000Z",
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "01K48D7YGVEYYZMZ6HQZ579ET0",
      "type": "image",
      "url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/original/01K48D7YGVEYYZMZ6HQZ579ET0.png",
      "text_url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/original/01K48D7YGVEYYZMZ6HQZ579ET0.png",
      "preview_url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/small/01K48D7YGVEYYZMZ6HQZ579ET0.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": "L8K54x,hfQ,h,hjvfQjvfQfQfQfQ"
    }
  ],
  "mentions": [
    {
      "id": "014HZBWCFX2KRE5R0YTT30X5C4",
      "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": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://gotosocial/users/cookie"
  ],
  "id": "http://pasture-one-actor/activity/lcv0Gsa7AIU",
  "published": "2025-09-03T18:25:52Z",
  "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/object/7FtmJvstRFk",
    "published": "2025-09-03T18:25:52Z",
    "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": "01K48D7YW0WFJS0Y3W3NC23FP1",
  "created_at": "2025-09-03T18:25:52.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/7FtmJvstRFk",
  "url": "http://pasture-one-actor/object/7FtmJvstRFk",
  "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": "01K48D4GXYW9KT1VG7A7FX4SYD",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": true,
    "discoverable": false,
    "bot": false,
    "created_at": "2025-09-03T18:23:59.442Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://gotosocial/assets/default_avatars/GoToSocial_icon4.png",
    "avatar_static": "http://gotosocial/assets/default_avatars/GoToSocial_icon4.png",
    "header": "http://gotosocial/assets/default_header.png",
    "header_static": "http://gotosocial/assets/default_header.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 74,
    "last_status_at": "2025-09-03T18:25:52.000Z",
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "01K48D7Z5XH530WFHXGK9PXD6Q",
      "type": "image",
      "url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/original/01K48D7Z5XH530WFHXGK9PXD6Q.png",
      "text_url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/original/01K48D7Z5XH530WFHXGK9PXD6Q.png",
      "preview_url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/small/01K48D7Z5XH530WFHXGK9PXD6Q.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": "L14z:Cu5fQu5u5j[fQj[fQfQfQfQ"
    }
  ],
  "mentions": [
    {
      "id": "014HZBWCFX2KRE5R0YTT30X5C4",
      "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": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://gotosocial/users/cookie"
  ],
  "id": "http://pasture-one-actor/activity/4_Qn6g2iJ6Y",
  "published": "2025-09-03T18:25:52Z",
  "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/object/besqYVCNHGg",
    "published": "2025-09-03T18:25:52Z",
    "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": "01K48D7YW0RXE4AWBJNXVTH47W",
  "created_at": "2025-09-03T18:25:52.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/besqYVCNHGg",
  "url": "http://pasture-one-actor/object/besqYVCNHGg",
  "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": "01K48D4GXYW9KT1VG7A7FX4SYD",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": true,
    "discoverable": false,
    "bot": false,
    "created_at": "2025-09-03T18:23:59.442Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://gotosocial/assets/default_avatars/GoToSocial_icon4.png",
    "avatar_static": "http://gotosocial/assets/default_avatars/GoToSocial_icon4.png",
    "header": "http://gotosocial/assets/default_header.png",
    "header_static": "http://gotosocial/assets/default_header.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 75,
    "last_status_at": "2025-09-03T18:25:52.000Z",
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "01K48D7ZTM4PV78EPWTY9XBF0X",
      "type": "image",
      "url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/original/01K48D7ZTM4PV78EPWTY9XBF0X.png",
      "text_url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/original/01K48D7ZTM4PV78EPWTY9XBF0X.png",
      "preview_url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/small/01K48D7ZTM4PV78EPWTY9XBF0X.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": "014HZBWCFX2KRE5R0YTT30X5C4",
      "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": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://gotosocial/users/cookie"
  ],
  "id": "http://pasture-one-actor/activity/Xu6x2_HaSJ0",
  "published": "2025-09-03T18:25:53Z",
  "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/object/wNOwtkUPH9U",
    "published": "2025-09-03T18:25:53Z",
    "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": "01K48D7ZV85JYETWMVMN125J4T",
  "created_at": "2025-09-03T18:25:53.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/wNOwtkUPH9U",
  "url": "http://pasture-one-actor/object/wNOwtkUPH9U",
  "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": "01K48D4GXYW9KT1VG7A7FX4SYD",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": true,
    "discoverable": false,
    "bot": false,
    "created_at": "2025-09-03T18:23:59.442Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "avatar": "http://gotosocial/assets/default_avatars/GoToSocial_icon4.png",
    "avatar_static": "http://gotosocial/assets/default_avatars/GoToSocial_icon4.png",
    "header": "http://gotosocial/assets/default_header.png",
    "header_static": "http://gotosocial/assets/default_header.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 76,
    "last_status_at": "2025-09-03T18:25:53.000Z",
    "emojis": [],
    "fields": []
  },
  "media_attachments": [
    {
      "id": "01K48D80GHNHRDRGQ1FSMP4T70",
      "type": "image",
      "url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/original/01K48D80GHNHRDRGQ1FSMP4T70.png",
      "text_url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/original/01K48D80GHNHRDRGQ1FSMP4T70.png",
      "preview_url": "http://gotosocial/fileserver/01K48D4GXYW9KT1VG7A7FX4SYD/attachment/small/01K48D80GHNHRDRGQ1FSMP4T70.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": "014HZBWCFX2KRE5R0YTT30X5C4",
      "username": "cookie",
      "url": "http://gotosocial/@cookie",
      "acct": "cookie"
    }
  ],
  "tags": [],
  "emojis": [],
  "card": null,
  "poll": null
}