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/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/activity/ZkRSAhfoVbc",
"published": "2025-10-04T15:41:28Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/object/n7CcFEXVRiU",
"published": "2025-10-04T15:41:28Z",
"content": "no description",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/b2d746d1-7f9f-4afe-b2ed-25294046783b.png"
}
}
}
sharkey
{
"id": "adg08yf4l0mw002i",
"uri": "http://pasture-one-actor/object/n7CcFEXVRiU",
"url": "http://pasture-one-actor/object/n7CcFEXVRiU",
"account": {
"id": "adg07agxl0mw0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-10-04T15:40:10.305Z",
"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": "2025-10-04T15:41:28.000Z",
"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": "adg08ywzl0mw002h",
"type": "image",
"url": "http://pasture-one-actor/images/b2d746d1-7f9f-4afe-b2ed-25294046783b.png",
"remote_url": "http://pasture-one-actor/images/b2d746d1-7f9f-4afe-b2ed-25294046783b.png",
"preview_url": "http://pasture-one-actor/images/b2d746d1-7f9f-4afe-b2ed-25294046783b.png",
"text_url": "http://pasture-one-actor/images/b2d746d1-7f9f-4afe-b2ed-25294046783b.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": "e28%;hu6fQu6fQu6fkfQfkfQfQfQfQfQfQu6fkfQfkfQfQfQfQfQfQ"
}
],
"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/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/activity/KholB9unWiU",
"published": "2025-10-04T15:41:29Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/object/7KQHYHg7igI",
"published": "2025-10-04T15:41:29Z",
"content": "name, summary and content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/e3f46f36-ab73-476c-9b16-c34980156f8d.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
sharkey
{
"id": "adg08z6wl0mw002k",
"uri": "http://pasture-one-actor/object/7KQHYHg7igI",
"url": "http://pasture-one-actor/object/7KQHYHg7igI",
"account": {
"id": "adg07agxl0mw0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-10-04T15:40:10.305Z",
"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": "2025-10-04T15:41:29.000Z",
"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": "adg08zcol0mw002j",
"type": "image",
"url": "http://pasture-one-actor/images/e3f46f36-ab73-476c-9b16-c34980156f8d.png",
"remote_url": "http://pasture-one-actor/images/e3f46f36-ab73-476c-9b16-c34980156f8d.png",
"preview_url": "http://pasture-one-actor/images/e3f46f36-ab73-476c-9b16-c34980156f8d.png",
"text_url": "http://pasture-one-actor/images/e3f46f36-ab73-476c-9b16-c34980156f8d.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": "e00n~=k]fQk]fQk]fkfQfkfQfQfQfQfQfQk]fkfQfkfQfQfQfQfQfQ"
}
],
"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/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/activity/J-_ckGZconA",
"published": "2025-10-04T15:41:29Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/object/6i2lRohYlTA",
"published": "2025-10-04T15:41:29Z",
"content": "only name",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"name": "name",
"imageType": "image/jpeg"
}
]
}
}
sharkey
{
"id": "adg08z6wl0mw002m",
"uri": "http://pasture-one-actor/object/6i2lRohYlTA",
"url": "http://pasture-one-actor/object/6i2lRohYlTA",
"account": {
"id": "adg07agxl0mw0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-10-04T15:40:10.305Z",
"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": "2025-10-04T15:41:29.000Z",
"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": "adg08zual0mw002l",
"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/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/activity/GJ22BUI-nE8",
"published": "2025-10-04T15:41:30Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/object/R7lcAYIXS-w",
"published": "2025-10-04T15:41:30Z",
"content": "only summary",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/8d2d1910-a04c-419e-a6cf-22605206eec3.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
sharkey
{
"id": "adg08zyol0mw002o",
"uri": "http://pasture-one-actor/object/R7lcAYIXS-w",
"url": "http://pasture-one-actor/object/R7lcAYIXS-w",
"account": {
"id": "adg07agxl0mw0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-10-04T15:40:10.305Z",
"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": "2025-10-04T15:41:30.000Z",
"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": "adg0909ml0mw002n",
"type": "image",
"url": "http://pasture-one-actor/images/8d2d1910-a04c-419e-a6cf-22605206eec3.png",
"remote_url": "http://pasture-one-actor/images/8d2d1910-a04c-419e-a6cf-22605206eec3.png",
"preview_url": "http://pasture-one-actor/images/8d2d1910-a04c-419e-a6cf-22605206eec3.png",
"text_url": "http://pasture-one-actor/images/8d2d1910-a04c-419e-a6cf-22605206eec3.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": "e19K3By+fQy+fQy+j@fQj@fQfQfQfQfQfQy+j@fQj@fQfQfQfQfQfQ"
}
],
"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/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/activity/xsis7-gM9bM",
"published": "2025-10-04T15:41:30Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/object/KcXqG8z64as",
"published": "2025-10-04T15:41:30Z",
"content": "only content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/a748eb80-0ed0-4c77-8ced-8f1331cb847a.png",
"content": "content"
}
}
}
sharkey
{
"id": "adg08zyol0mw002q",
"uri": "http://pasture-one-actor/object/KcXqG8z64as",
"url": "http://pasture-one-actor/object/KcXqG8z64as",
"account": {
"id": "adg07agxl0mw0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-10-04T15:40:10.305Z",
"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": "2025-10-04T15:41:30.000Z",
"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": "adg090q4l0mw002p",
"type": "image",
"url": "http://pasture-one-actor/images/a748eb80-0ed0-4c77-8ced-8f1331cb847a.png",
"remote_url": "http://pasture-one-actor/images/a748eb80-0ed0-4c77-8ced-8f1331cb847a.png",
"preview_url": "http://pasture-one-actor/images/a748eb80-0ed0-4c77-8ced-8f1331cb847a.png",
"text_url": "http://pasture-one-actor/images/a748eb80-0ed0-4c77-8ced-8f1331cb847a.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": "e06H7YxafQxafQxafQfQfQfQfQfQfQfQfQxafQfQfQfQfQfQfQfQfQ"
}
],
"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/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/activity/W28niVOtYS4",
"published": "2025-10-04T15:41:31Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://sharkey/users/adg05og8rvr00003"
],
"id": "http://pasture-one-actor/object/J-q74R5EojQ",
"published": "2025-10-04T15:41:31Z",
"content": "no comment in attachment; reused image",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
]
}
}
sharkey
{
"id": "adg090qgl0mw002r",
"uri": "http://pasture-one-actor/object/J-q74R5EojQ",
"url": "http://pasture-one-actor/object/J-q74R5EojQ",
"account": {
"id": "adg07agxl0mw0004",
"username": "actor",
"acct": "actor@pasture-one-actor",
"fqn": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"created_at": "2025-10-04T15:40:10.305Z",
"followers_count": 0,
"following_count": 0,
"statuses_count": 78,
"note": "",
"url": "http://pasture-one-actor/actor",
"uri": "http://pasture-one-actor/actor",
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