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": [
"http://sharkey/users/acg3ru0zh3uf0003",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/p-De8lAvUxU",
"published": "2025-09-09T12:43:14Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/acg3ru0zh3uf0003"
],
"id": "http://pasture-one-actor/object/emoNhkgs38s",
"published": "2025-09-09T12:43:14Z",
"content": "no description",
"attachment": {
"type": "Document",
"url": "http://pasture-one-actor/images/100.png"
}
}
}
pyfedi
{
"id": 64,
"user_id": 2,
"community_id": 1,
"title": "[Microblog] no description",
"deleted": false,
"nsfw": false,
"sticky": false,
"published": "2025-09-09T12:28:10.404708Z",
"ap_id": "http://pasture-one-actor/object/oXuVRv_p_cA",
"local": false,
"language_id": 2,
"removed": false,
"locked": false,
"body": "no description",
"url": "http://pasture-one-actor/images/100.png",
"thumbnail_url": "http://pasture-one-actor/images/100.png",
"small_thumbnail_url": "http://pasture-one-actor/images/100.png"
}
sharkey
{
"id": "acg3vg7ktn88002g",
"uri": "http://pasture-one-actor/object/emoNhkgs38s",
"url": "http://pasture-one-actor/object/emoNhkgs38s",
"account": {
"id": "acg3tlswtn880004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-09-09T12:41:47.936Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 71,
"note": "",
"url": "http://pasture-one-actor/actor",
"uri": "http://pasture-one-actor/actor",
"avatar": "https://dev.joinsharkey.org/static-assets/avatar.png",
"avatar_static": "https://dev.joinsharkey.org/static-assets/avatar.png",
"header": "https://dev.joinsharkey.org/static-assets/transparent.png",
"header_static": "https://dev.joinsharkey.org/static-assets/transparent.png",
"emojis": [],
"moved": null,
"fields": [],
"bot": false,
"discoverable": true,
"noindex": false,
"group": null,
"suspended": false,
"limited": false
},
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"content": "<p>no description</p>",
"content_type": "text/x.misskeymarkdown",
"text": "no description",
"created_at": "2025-09-09T12:43:14.000Z",
"edited_at": null,
"emojis": [],
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"reblogged": false,
"favourited": false,
"muted": false,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"media_attachments": [
{
"id": "acg3vgt6tn88002f",
"type": "image",
"url": "http://pasture-one-actor/images/100.png",
"remote_url": "http://pasture-one-actor/images/100.png",
"preview_url": "http://pasture-one-actor/images/100.png",
"text_url": "http://pasture-one-actor/images/100.png",
"meta": {
"width": 40,
"height": 40,
"original": {
"width": 40,
"height": 40,
"size": "40x40",
"aspect": 1,
"frame_rate": "undefined"
},
"size": "40x40",
"aspect": 1
},
"description": null,
"blurhash": "e38L+EswfQswfQswfRfQfRfQfQfQfQfQfQswfRfQfRfQfQfQfQfQfQ"
}
],
"mentions": [],
"tags": [],
"card": null,
"poll": null,
"application": null,
"language": null,
"pinned": false,
"bookmarked": false,
"quote": null,
"reactions": []
}
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://sharkey/users/acg3ru0zh3uf0003",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/HAZKfy0j9RY",
"published": "2025-09-09T12:43:15Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/acg3ru0zh3uf0003"
],
"id": "http://pasture-one-actor/object/AUYDoFJxAX0",
"published": "2025-09-09T12:43:15Z",
"content": "name and summary",
"attachment": {
"type": "Document",
"url": "http://pasture-one-actor/images/100.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
pyfedi
{
"id": 65,
"user_id": 2,
"community_id": 1,
"title": "[Microblog] name and summary",
"deleted": false,
"nsfw": false,
"sticky": false,
"published": "2025-09-09T12:28:11.240021Z",
"ap_id": "http://pasture-one-actor/object/eXayMp18u8o",
"local": false,
"language_id": 2,
"removed": false,
"locked": false,
"body": "name and summary",
"url": "http://pasture-one-actor/images/100.png",
"thumbnail_url": "http://pasture-one-actor/images/100.png",
"small_thumbnail_url": "http://pasture-one-actor/images/100.png"
}
sharkey
{
"id": "acg3vgzctn88002i",
"uri": "http://pasture-one-actor/object/AUYDoFJxAX0",
"url": "http://pasture-one-actor/object/AUYDoFJxAX0",
"account": {
"id": "acg3tlswtn880004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-09-09T12:41:47.936Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 72,
"note": "",
"url": "http://pasture-one-actor/actor",
"uri": "http://pasture-one-actor/actor",
"avatar": "https://dev.joinsharkey.org/static-assets/avatar.png",
"avatar_static": "https://dev.joinsharkey.org/static-assets/avatar.png",
"header": "https://dev.joinsharkey.org/static-assets/transparent.png",
"header_static": "https://dev.joinsharkey.org/static-assets/transparent.png",
"emojis": [],
"moved": null,
"fields": [],
"bot": false,
"discoverable": true,
"noindex": false,
"group": null,
"suspended": false,
"limited": false
},
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"content": "<p>name and summary</p>",
"content_type": "text/x.misskeymarkdown",
"text": "name and summary",
"created_at": "2025-09-09T12:43:15.000Z",
"edited_at": null,
"emojis": [],
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"reblogged": false,
"favourited": false,
"muted": false,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"media_attachments": [
{
"id": "acg3vhcrtn88002h",
"type": "image",
"url": "http://pasture-one-actor/images/100.png",
"remote_url": "http://pasture-one-actor/images/100.png",
"preview_url": "http://pasture-one-actor/images/100.png",
"text_url": "http://pasture-one-actor/images/100.png",
"meta": {
"width": 40,
"height": 40,
"original": {
"width": 40,
"height": 40,
"size": "40x40",
"aspect": 1,
"frame_rate": "undefined"
},
"size": "40x40",
"aspect": 1
},
"description": "name",
"blurhash": "e2N4pO}2fQ}2fQ}2jufQjufQfQfQfQfQfQ}2jufQjufQfQfQfQfQfQ"
}
],
"mentions": [],
"tags": [],
"card": null,
"poll": null,
"application": null,
"language": null,
"pinned": false,
"bookmarked": false,
"quote": null,
"reactions": []
}
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://sharkey/users/acg3ru0zh3uf0003",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/493d6cWYKVM",
"published": "2025-09-09T12:43:15Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/acg3ru0zh3uf0003"
],
"id": "http://pasture-one-actor/object/29HNPKQri9M",
"published": "2025-09-09T12:43:15Z",
"content": "only name",
"attachment": [
{
"type": "Document",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"name": "name",
"imageType": "image/jpeg"
}
]
}
}
pyfedi
{
"id": 66,
"user_id": 2,
"community_id": 1,
"title": "(content in post body)",
"deleted": false,
"nsfw": false,
"sticky": false,
"published": "2025-09-09T12:28:11.978979Z",
"ap_id": "http://pasture-one-actor/object/0dWYKOfEPHM",
"local": false,
"language_id": 2,
"removed": false,
"locked": false,
"body": "only name",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"thumbnail_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"small_thumbnail_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"alt_text": "name"
}
sharkey
{
"id": "acg3vgzctn88002k",
"uri": "http://pasture-one-actor/object/29HNPKQri9M",
"url": "http://pasture-one-actor/object/29HNPKQri9M",
"account": {
"id": "acg3tlswtn880004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-09-09T12:41:47.936Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 73,
"note": "",
"url": "http://pasture-one-actor/actor",
"uri": "http://pasture-one-actor/actor",
"avatar": "https://dev.joinsharkey.org/static-assets/avatar.png",
"avatar_static": "https://dev.joinsharkey.org/static-assets/avatar.png",
"header": "https://dev.joinsharkey.org/static-assets/transparent.png",
"header_static": "https://dev.joinsharkey.org/static-assets/transparent.png",
"emojis": [],
"moved": null,
"fields": [],
"bot": false,
"discoverable": true,
"noindex": false,
"group": null,
"suspended": false,
"limited": false
},
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"content": "<p>only name</p>",
"content_type": "text/x.misskeymarkdown",
"text": "only name",
"created_at": "2025-09-09T12:43:15.000Z",
"edited_at": null,
"emojis": [],
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"reblogged": false,
"favourited": false,
"muted": false,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"media_attachments": [
{
"id": "acg3vhxutn88002j",
"type": "image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"remote_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"preview_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"text_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"meta": {
"width": 1548,
"height": 1548,
"original": {
"width": 1548,
"height": 1548,
"size": "1548x1548",
"aspect": 1,
"frame_rate": "undefined"
},
"size": "1548x1548",
"aspect": 1
},
"description": "name",
"blurhash": "eQE_?c.}4.YJM^}fi{EVw[xu9JK[M~xI-T9+TJRPX2$$E]NFo}j1tO"
}
],
"mentions": [],
"tags": [],
"card": null,
"poll": null,
"application": null,
"language": null,
"pinned": false,
"bookmarked": false,
"quote": null,
"reactions": []
}
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://sharkey/users/acg3ru0zh3uf0003",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/g37RMtCBB6M",
"published": "2025-09-09T12:43:16Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/acg3ru0zh3uf0003"
],
"id": "http://pasture-one-actor/object/zu0Nn4cOEdU",
"published": "2025-09-09T12:43:16Z",
"content": "no comment in attachment",
"attachment": [
{
"type": "Document",
"url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
]
}
}
pyfedi
{
"id": 67,
"user_id": 2,
"community_id": 1,
"title": "no comment in attachment",
"deleted": false,
"nsfw": false,
"sticky": false,
"published": "2025-09-09T12:28:12.728627Z",
"ap_id": "http://pasture-one-actor/object/s3zWaOR3itI",
"local": false,
"language_id": 2,
"removed": false,
"locked": false,
"body": "no comment in attachment",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"thumbnail_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"small_thumbnail_url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
sharkey
{
"id": "acg3vhr4tn88002l",
"uri": "http://pasture-one-actor/object/zu0Nn4cOEdU",
"url": "http://pasture-one-actor/object/zu0Nn4cOEdU",
"account": {
"id": "acg3tlswtn880004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-09-09T12:41:47.936Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 74,
"note": "",
"url": "http://pasture-one-actor/actor",
"uri": "http://pasture-one-actor/actor",
"avatar": "https://dev.joinsharkey.org/static-assets/avatar.png",
"avatar_static": "https://dev.joinsharkey.org/static-assets/avatar.png",
"header": "https://dev.joinsharkey.org/static-assets/transparent.png",
"header_static": "https://dev.joinsharkey.org/static-assets/transparent.png",
"emojis": [],
"moved": null,
"fields": [],
"bot": false,
"discoverable": true,
"noindex": false,
"group": null,
"suspended": false,
"limited": false
},
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"content": "<p>no comment in attachment</p>",
"content_type": "text/x.misskeymarkdown",
"text": "no comment in attachment",
"created_at": "2025-09-09T12:43:16.000Z",
"edited_at": null,
"emojis": [],
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"reblogged": false,
"favourited": false,
"muted": false,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"media_attachments": [
{
"id": "acg3vhxutn88002j",
"type": "image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"remote_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"preview_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"text_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"meta": {
"width": 1548,
"height": 1548,
"original": {
"width": 1548,
"height": 1548,
"size": "1548x1548",
"aspect": 1,
"frame_rate": "undefined"
},
"size": "1548x1548",
"aspect": 1
},
"description": "name",
"blurhash": "eQE_?c.}4.YJM^}fi{EVw[xu9JK[M~xI-T9+TJRPX2$$E]NFo}j1tO"
}
],
"mentions": [],
"tags": [],
"card": null,
"poll": null,
"application": null,
"language": null,
"pinned": false,
"bookmarked": false,
"quote": null,
"reactions": []
}