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://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/activity/pbcnBqQRUxc",
"published": "2025-11-21T14:40:25Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/object/tyqmAuVaSl8",
"published": "2025-11-21T14:40:25Z",
"content": "no description",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/634d691a-ab66-4d57-8ca9-b45fbe9f487d.png"
}
}
}
sharkey
{
"id": "afcj7c14judd002i",
"uri": "http://pasture-one-actor/object/tyqmAuVaSl8",
"url": "http://pasture-one-actor/object/tyqmAuVaSl8",
"account": {
"id": "afcj5n5wjudd0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-11-21T14:39:06.116Z",
"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>no description</p>",
"content_type": "text/x.misskeymarkdown",
"text": "no description",
"created_at": "2025-11-21T14:40:25.000Z",
"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": "afcj7cnzjudd002h",
"type": "image",
"url": "http://pasture-one-actor/images/634d691a-ab66-4d57-8ca9-b45fbe9f487d.png",
"remote_url": "http://pasture-one-actor/images/634d691a-ab66-4d57-8ca9-b45fbe9f487d.png",
"preview_url": "http://pasture-one-actor/images/634d691a-ab66-4d57-8ca9-b45fbe9f487d.png",
"text_url": "http://pasture-one-actor/images/634d691a-ab66-4d57-8ca9-b45fbe9f487d.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": "e03oVzqEfQqEfQqEfkfQfkfQfQfQfQfQfQqEfkfQfkfQfQfQfQfQfQ"
}
],
"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": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/activity/pCtIiChlt50",
"published": "2025-11-21T14:40:26Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/object/v_TuzEPcR5c",
"published": "2025-11-21T14:40:26Z",
"content": "name, summary and content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/85a4d109-947f-4384-b433-5ecfd52cd361.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
sharkey
{
"id": "afcj7cswjudd002k",
"uri": "http://pasture-one-actor/object/v_TuzEPcR5c",
"url": "http://pasture-one-actor/object/v_TuzEPcR5c",
"account": {
"id": "afcj5n5wjudd0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-11-21T14:39:06.116Z",
"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>name, summary and content</p>",
"content_type": "text/x.misskeymarkdown",
"text": "name, summary and content",
"created_at": "2025-11-21T14:40:26.000Z",
"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": "afcj7d3pjudd002j",
"type": "image",
"url": "http://pasture-one-actor/images/85a4d109-947f-4384-b433-5ecfd52cd361.png",
"remote_url": "http://pasture-one-actor/images/85a4d109-947f-4384-b433-5ecfd52cd361.png",
"preview_url": "http://pasture-one-actor/images/85a4d109-947f-4384-b433-5ecfd52cd361.png",
"text_url": "http://pasture-one-actor/images/85a4d109-947f-4384-b433-5ecfd52cd361.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": "e05h^lxqfQxqfQxqfjfQfjfQfQfQfQfQfQxqfjfQfjfQfQfQfQfQfQ"
}
],
"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": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/activity/bQqfMeg_bgk",
"published": "2025-11-21T14:40:26Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/object/3A1U6-nRULs",
"published": "2025-11-21T14:40:26Z",
"content": "only name",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"name": "name",
"imageType": "image/jpeg"
}
]
}
}
sharkey
{
"id": "afcj7cswjudd002m",
"uri": "http://pasture-one-actor/object/3A1U6-nRULs",
"url": "http://pasture-one-actor/object/3A1U6-nRULs",
"account": {
"id": "afcj5n5wjudd0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-11-21T14:39:06.116Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 75,
"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": "2025-11-21T14:40:26.000Z",
"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": "afcj7dlujudd002l",
"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": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/activity/MHO6owbRqD8",
"published": "2025-11-21T14:40:27Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/object/qSz0ocSs4PM",
"published": "2025-11-21T14:40:27Z",
"content": "only summary",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/64d16ce6-6689-46f1-984c-9ed3d6d6140b.png",
"summary": "summary"
}
}
}
sharkey
{
"id": "afcj7dkojudd002o",
"uri": "http://pasture-one-actor/object/qSz0ocSs4PM",
"url": "http://pasture-one-actor/object/qSz0ocSs4PM",
"account": {
"id": "afcj5n5wjudd0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-11-21T14:39:06.116Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 76,
"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 summary</p>",
"content_type": "text/x.misskeymarkdown",
"text": "only summary",
"created_at": "2025-11-21T14:40:27.000Z",
"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": "afcj7dzqjudd002n",
"type": "image",
"url": "http://pasture-one-actor/images/64d16ce6-6689-46f1-984c-9ed3d6d6140b.png",
"remote_url": "http://pasture-one-actor/images/64d16ce6-6689-46f1-984c-9ed3d6d6140b.png",
"preview_url": "http://pasture-one-actor/images/64d16ce6-6689-46f1-984c-9ed3d6d6140b.png",
"text_url": "http://pasture-one-actor/images/64d16ce6-6689-46f1-984c-9ed3d6d6140b.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": "e07,rZ$%fQ$%fQ$%jtfQjtfQfQfQfQfQfQ$%jtfQjtfQfQfQfQfQfQ"
}
],
"mentions": [],
"tags": [],
"card": null,
"poll": null,
"application": null,
"language": null,
"pinned": false,
"bookmarked": false,
"quote": null,
"reactions": []
}
Example 5¶
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://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/activity/3fpMK71OYuw",
"published": "2025-11-21T14:40:28Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/object/p6Ab1lH6wag",
"published": "2025-11-21T14:40:28Z",
"content": "only content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/e5b98b21-529f-4ed8-bb03-c60aba4781d7.png",
"content": "content"
}
}
}
sharkey
{
"id": "afcj7ecgjudd002q",
"uri": "http://pasture-one-actor/object/p6Ab1lH6wag",
"url": "http://pasture-one-actor/object/p6Ab1lH6wag",
"account": {
"id": "afcj5n5wjudd0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-11-21T14:39:06.116Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 77,
"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 content</p>",
"content_type": "text/x.misskeymarkdown",
"text": "only content",
"created_at": "2025-11-21T14:40:28.000Z",
"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": "afcj7efhjudd002p",
"type": "image",
"url": "http://pasture-one-actor/images/e5b98b21-529f-4ed8-bb03-c60aba4781d7.png",
"remote_url": "http://pasture-one-actor/images/e5b98b21-529f-4ed8-bb03-c60aba4781d7.png",
"preview_url": "http://pasture-one-actor/images/e5b98b21-529f-4ed8-bb03-c60aba4781d7.png",
"text_url": "http://pasture-one-actor/images/e5b98b21-529f-4ed8-bb03-c60aba4781d7.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": "e025cWoMfQoMfQoMfQfQfQfQfQfQfQfQfQoMfQfQfQfQfQfQfQfQfQ"
}
],
"mentions": [],
"tags": [],
"card": null,
"poll": null,
"application": null,
"language": null,
"pinned": false,
"bookmarked": false,
"quote": null,
"reactions": []
}
Example 6¶
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://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/activity/2nfVpesdawI",
"published": "2025-11-21T14:40:28Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/afcj40xfmzy00003"
],
"id": "http://pasture-one-actor/object/aKuQaElAWRU",
"published": "2025-11-21T14:40:28Z",
"content": "no comment in attachment; reused image",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
]
}
}
sharkey
{
"id": "afcj7ecgjudd002r",
"uri": "http://pasture-one-actor/object/aKuQaElAWRU",
"url": "http://pasture-one-actor/object/aKuQaElAWRU",
"account": {
"id": "afcj5n5wjudd0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-11-21T14:39:06.116Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 78,
"note": "",
"url": "http://pasture-one-actor/actor",
"uri": "http://pasture-one-actor/actor",
"avatar": "https://dev.joinsharkey.org/static-assets/avatar.png",
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