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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.

Support table

attachment akkoma friendica gotosocial hollo mastodon misskey mitra pleroma sharkey
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”
}
- - - - - - - - -
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”,
  “name”: “name”,
  “summary”: “summary”,
  “content”: “content”
}
name name summary summary summary name name summary name
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
    “name”: “name”,
    “imageType”: “image/jpeg”
  }
]
name - - name name ⚠️ - name ⚠️
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”
  }
]
- - - - - ⚠️ - - ⚠️

Details

attachment media_attachments Example
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”
}
{
  “blurhash”: null,
  “description”: null,
  “id”: “983810756”,
  “pleroma”: {
    “mime_type”: “application/octet-stream”
  },
  “preview_url”: “http://pasture-one-actor/images/100.png”,
  “remote_url”: “http://pasture-one-actor/images/100.png”,
  “text_url”: “http://pasture-one-actor/images/100.png”,
  “type”: “unknown”,
  “url”: “http://pasture-one-actor/images/100.png”
}
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”,
  “name”: “name”,
  “summary”: “summary”,
  “content”: “content”
}
{
  “blurhash”: null,
  “description”: “name”,
  “id”: “983810756”,
  “pleroma”: {
    “mime_type”: “application/octet-stream”
  },
  “preview_url”: “http://pasture-one-actor/images/100.png”,
  “remote_url”: “http://pasture-one-actor/images/100.png”,
  “text_url”: “http://pasture-one-actor/images/100.png”,
  “type”: “unknown”,
  “url”: “http://pasture-one-actor/images/100.png”
}
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
    “name”: “name”,
    “imageType”: “image/jpeg”
  }
]
{
  “blurhash”: null,
  “description”: “name”,
  “id”: “-751667840”,
  “pleroma”: {
    “mime_type”: “application/octet-stream”
  },
  “preview_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “remote_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “text_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “type”: “unknown”,
  “url”: “http://pasture-one-actor/assets/FediverseLogo.png”
}
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”
  }
]
{
  “blurhash”: null,
  “description”: null,
  “id”: “-751667840”,
  “pleroma”: {
    “mime_type”: “application/octet-stream”
  },
  “preview_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “remote_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “text_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “type”: “unknown”,
  “url”: “http://pasture-one-actor/assets/FediverseLogo.png”
}
attachment media_attachments Example
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”
}
{
  “id”: “9”,
  “type”: “image”,
  “url”: “http://friendica/photo/preview/9”,
  “preview_url”: “http://friendica/photo/preview/640/9”,
  “remote_url”: “http://pasture-one-actor/images/100.png”,
  “text_url”: “http://pasture-one-actor/images/100.png”,
  “description”: null,
  “blurhash”: “|7OL,W?KfQ?KfQ?KfQ?KfQ?Kj[fQj[fQj[fQj[fQfQfQfQfQfQfQfQfQfQ?Kj[fQj[fQj[fQj[fQfQfQfQfQfQfQfQfQfQ?Kj[fQj[fQj[fQj[fQfQfQfQfQfQfQfQfQfQ?Kj[fQj[fQj[fQj[fQfQfQfQfQfQfQfQfQfQ”,
  “meta”: {
    “original”: {
      “width”: 40,
      “height”: 40,
      “size”: “40x40”,
      “aspect”: 1
    }
  }
}
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”,
  “name”: “name”,
  “summary”: “summary”,
  “content”: “content”
}
{
  “id”: “11”,
  “type”: “image”,
  “url”: “http://friendica/photo/preview/11”,
  “preview_url”: “http://friendica/photo/preview/640/11”,
  “remote_url”: “http://pasture-one-actor/images/100.png”,
  “text_url”: “http://pasture-one-actor/images/100.png”,
  “description”: “name”,
  “blurhash”: “|39PItxNfQxNfQxNfQxNfQxNjufQjufQjufQjufQfQfQfQfQfQfQfQfQfQxNjufQjufQjufQjufQfQfQfQfQfQfQfQfQfQxNjufQjufQjufQjufQfQfQfQfQfQfQfQfQfQxNjufQjufQjufQjufQfQfQfQfQfQfQfQfQfQ”,
  “meta”: {
    “original”: {
      “width”: 40,
      “height”: 40,
      “size”: “40x40”,
      “aspect”: 1
    }
  }
}
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
    “name”: “name”,
    “imageType”: “image/jpeg”
  }
]
null
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”
  }
]
null
attachment media_attachments Example
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”
}
{
  “id”: “01K3GVARZFVVXRP68N7V82VZSV”,
  “type”: “image”,
  “url”: “http://gotosocial/fileserver/01K3GV8459F044M7E2J13WTR56/attachment/original/01K3GVARZFVVXRP68N7V82VZSV.png”,
  “text_url”: “http://gotosocial/fileserver/01K3GV8459F044M7E2J13WTR56/attachment/original/01K3GVARZFVVXRP68N7V82VZSV.png”,
  “preview_url”: “http://gotosocial/fileserver/01K3GV8459F044M7E2J13WTR56/attachment/small/01K3GVARZFVVXRP68N7V82VZSV.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”: “L6O1OT}xfQ}x}xoMfQoMfQfQfQfQ”
}
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”,
  “name”: “name”,
  “summary”: “summary”,
  “content”: “content”
}
{
  “id”: “01K3GVASNEY5Z8489RGSAK97HM”,
  “type”: “image”,
  “url”: “http://gotosocial/fileserver/01K3GV8459F044M7E2J13WTR56/attachment/original/01K3GVASNEY5Z8489RGSAK97HM.png”,
  “text_url”: “http://gotosocial/fileserver/01K3GV8459F044M7E2J13WTR56/attachment/original/01K3GVASNEY5Z8489RGSAK97HM.png”,
  “preview_url”: “http://gotosocial/fileserver/01K3GV8459F044M7E2J13WTR56/attachment/small/01K3GVASNEY5Z8489RGSAK97HM.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”: “L58b*LubfQububkAfQkAfQfQfQfQ”
}
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
    “name”: “name”,
    “imageType”: “image/jpeg”
  }
]
null
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”
  }
]
null
attachment media_attachments Example
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”
}
{
  “id”: “0198cb8c-c77c-7c21-a39a-295a928d55ca”,
  “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
}
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”,
  “name”: “name”,
  “summary”: “summary”,
  “content”: “content”
}
{
  “id”: “0198cb8c-ca6c-7185-ae22-5f1e4e892b0c”,
  “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,
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    }
  },
  “description”: “summary”,
  “blurhash”: null
}
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
    “name”: “name”,
    “imageType”: “image/jpeg”
  }
]
{
  “id”: “0198cb8c-cd6b-7ce3-9fbe-04837257b2b5”,
  “type”: “text”,
  “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
}
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”
  }
]
{
  “id”: “0198cb8c-d043-751e-972b-6668cf07c622”,
  “type”: “text”,
  “url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “preview_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “remote_url”: null,
  “text_url”: null,
  “meta”: {
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      “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
}
attachment media_attachments Example
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”
}
{
  “id”: “115032310669008779”,
  “type”: “image”,
  “url”: “http://localhost:2970/system/cache/media_attachments/files/115/032/310/669/008/779/original/3be46e4361bd6937.png”,
  “preview_url”: “http://localhost:2970/system/cache/media_attachments/files/115/032/310/669/008/779/small/3be46e4361bd6937.png”,
  “remote_url”: “http://pasture-one-actor/images/100.png”,
  “preview_remote_url”: null,
  “text_url”: null,
  “meta”: {
    “original”: {
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      “height”: 40,
      “size”: “40x40”,
      “aspect”: 1.0
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    “small”: {
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      “size”: “40x40”,
      “aspect”: 1.0
    }
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}
{
  “type”: “Document”,
  “url”: “http://pasture-one-actor/images/100.png”,
  “name”: “name”,
  “summary”: “summary”,
  “content”: “content”
}
{
  “id”: “115032310733224702”,
  “type”: “image”,
  “url”: “http://localhost:2970/system/cache/media_attachments/files/115/032/310/733/224/702/original/2afc80ec2fa749be.png”,
  “preview_url”: “http://localhost:2970/system/cache/media_attachments/files/115/032/310/733/224/702/small/2afc80ec2fa749be.png”,
  “remote_url”: “http://pasture-one-actor/images/100.png”,
  “preview_remote_url”: null,
  “text_url”: null,
  “meta”: {
    “original”: {
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      “height”: 40,
      “size”: “40x40”,
      “aspect”: 1.0
    },
    “small”: {
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      “size”: “40x40”,
      “aspect”: 1.0
    }
  },
  “description”: “summary”,
  “blurhash”: “U1KoJE_KfQ_K_Kj[fQj[fQfQfQfQ_Kj[fQj[“
}
[
  {
    “type”: “Document”,
    “url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
    “name”: “name”,
    “imageType”: “image/jpeg”
  }
]
{
  “id”: “115032310798550362”,
  “type”: “unknown”,
  “url”: “http://mastodon/media_proxy/115032310798550362/original”,
  “preview_url”: “http://mastodon/media_proxy/115032310798550362/small”,
  “remote_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “preview_remote_url”: null,
  “text_url”: null,
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}
[
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    “type”: “Document”,
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]
{
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  “url”: “http://mastodon/media_proxy/115032310885795698/original”,
  “preview_url”: “http://mastodon/media_proxy/115032310885795698/small”,
  “remote_url”: “http://pasture-one-actor/assets/FediverseLogo.png”,
  “preview_remote_url”: null,
  “text_url”: null,
  “meta”: null,
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}
attachment files fileIds Example
{
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  “url”: “http://pasture-one-actor/images/100.png”
}
[
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    “name”: “100.png”,
    “type”: “image/png”,
    “md5”: “e7128219aca6062fd7abc023021cce5d”,
    “size”: 0,
    “isSensitive”: false,
    “blurhash”: “e1I];n|_fQ|_fQ|_jtfQjtfQfQfQfQfQfQ|_jtfQjtfQfQfQfQfQfQ”,
    “properties”: {
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    },
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    “thumbnailUrl”: “http://pasture-one-actor/images/100.png”,
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{
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[
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      “height”: 40
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    “thumbnailUrl”: “http://pasture-one-actor/images/100.png”,
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-
attachment media_attachments Example
{
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}
{
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{
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attachment media_attachments Example
{
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}
{
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  “pleroma”: {
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  “remote_url”: “http://pasture-one-actor/images/100.png”,
  “text_url”: “http://pasture-one-actor/images/100.png”,
  “type”: “unknown”,
  “url”: “http://pasture-one-actor/images/100.png”
}
{
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  “name”: “name”,
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{
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  “text_url”: “http://pasture-one-actor/images/100.png”,
  “type”: “unknown”,
  “url”: “http://pasture-one-actor/images/100.png”
}
[
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    “imageType”: “image/jpeg”
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}
[
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