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://hollo/@john",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/cN01GzDLQhY",
"published": "2025-11-08T13:18:53Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/object/vLTxLve3L5U",
"published": "2025-11-08T13:18:53Z",
"content": "no description",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/4956dbca-8d0a-4142-8761-7307c27907da.png"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a639e-a648-788e-b37a-f8147fc76be4",
"created_at": "2025-11-08T13:18:53.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/vLTxLve3L5U",
"url": "http://pasture-one-actor/object/vLTxLve3L5U",
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"favourited": false,
"reblogged": false,
"muted": false,
"bookmarked": false,
"pinned": false,
"content": "no description",
"reblog": null,
"quote_id": null,
"quote": null,
"application": null,
"account": {
"id": "019a639c-17b5-7c5f-857b-ea23de5bacce",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-08T13:16:05.368Z",
"note": "",
"url": "http://pasture-one-actor/actor",
"avatar": "http://hollo/image/avatars/original/missing.png",
"avatar_static": "http://hollo/image/avatars/original/missing.png",
"header": "http://hollo/image/headers/original/missing.png",
"header_static": "http://hollo/image/headers/original/missing.png",
"followers_count": 0,
"following_count": 0,
"statuses_count": 0,
"moved": null,
"last_status_at": null,
"emojis": [],
"fields": []
},
"media_attachments": [
{
"id": "019a639e-a7c6-7032-9158-75e2961399de",
"type": "image",
"url": "http://pasture-one-actor/images/4956dbca-8d0a-4142-8761-7307c27907da.png",
"preview_url": "http://pasture-one-actor/images/4956dbca-8d0a-4142-8761-7307c27907da.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
}
],
"mentions": [],
"tags": [],
"card": null,
"emojis": [],
"emoji_reactions": [],
"poll": null,
"filtered": 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": [
"http://hollo/@john",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/cxRS9fH6r7U",
"published": "2025-11-08T13:18:53Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/object/wrUuKiLynZI",
"published": "2025-11-08T13:18:53Z",
"content": "name, summary and content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/626de284-df78-4c40-921e-b3e81f6c47ef.png",
"name": "name",
"summary": "summary",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a639e-a648-788e-b37a-f81532cff636",
"created_at": "2025-11-08T13:18:53.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/wrUuKiLynZI",
"url": "http://pasture-one-actor/object/wrUuKiLynZI",
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"favourited": false,
"reblogged": false,
"muted": false,
"bookmarked": false,
"pinned": false,
"content": "name, summary and content",
"reblog": null,
"quote_id": null,
"quote": null,
"application": null,
"account": {
"id": "019a639c-17b5-7c5f-857b-ea23de5bacce",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-08T13:16:05.368Z",
"note": "",
"url": "http://pasture-one-actor/actor",
"avatar": "http://hollo/image/avatars/original/missing.png",
"avatar_static": "http://hollo/image/avatars/original/missing.png",
"header": "http://hollo/image/headers/original/missing.png",
"header_static": "http://hollo/image/headers/original/missing.png",
"followers_count": 0,
"following_count": 0,
"statuses_count": 0,
"moved": null,
"last_status_at": null,
"emojis": [],
"fields": []
},
"media_attachments": [
{
"id": "019a639e-aa08-75d7-ba91-0fceb826d5e0",
"type": "image",
"url": "http://pasture-one-actor/images/626de284-df78-4c40-921e-b3e81f6c47ef.png",
"preview_url": "http://pasture-one-actor/images/626de284-df78-4c40-921e-b3e81f6c47ef.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": "summary",
"blurhash": null
}
],
"mentions": [],
"tags": [],
"card": null,
"emojis": [],
"emoji_reactions": [],
"poll": null,
"filtered": 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": [
"http://hollo/@john",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/TbZS3r5imlA",
"published": "2025-11-08T13:18:54Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/object/Z9NDYvLZvX8",
"published": "2025-11-08T13:18:54Z",
"content": "only name",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"name": "name",
"imageType": "image/jpeg"
}
],
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a639e-aa30-79b7-ae23-f1cb33c73e98",
"created_at": "2025-11-08T13:18:54.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/Z9NDYvLZvX8",
"url": "http://pasture-one-actor/object/Z9NDYvLZvX8",
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"favourited": false,
"reblogged": false,
"muted": false,
"bookmarked": false,
"pinned": false,
"content": "only name",
"reblog": null,
"quote_id": null,
"quote": null,
"application": null,
"account": {
"id": "019a639c-17b5-7c5f-857b-ea23de5bacce",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-08T13:16:05.368Z",
"note": "",
"url": "http://pasture-one-actor/actor",
"avatar": "http://hollo/image/avatars/original/missing.png",
"avatar_static": "http://hollo/image/avatars/original/missing.png",
"header": "http://hollo/image/headers/original/missing.png",
"header_static": "http://hollo/image/headers/original/missing.png",
"followers_count": 0,
"following_count": 0,
"statuses_count": 0,
"moved": null,
"last_status_at": null,
"emojis": [],
"fields": []
},
"media_attachments": [
{
"id": "019a639e-aca2-7897-a099-4ca5ff2b1cd6",
"type": "image",
"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
}
],
"mentions": [],
"tags": [],
"card": null,
"emojis": [],
"emoji_reactions": [],
"poll": null,
"filtered": 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": [
"http://hollo/@john",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/AMEVh-un0GE",
"published": "2025-11-08T13:18:55Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/object/13c0tXh2vK0",
"published": "2025-11-08T13:18:55Z",
"content": "only summary",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/87c89873-e30b-4a71-b5dd-bf70cac1b10f.png",
"name": "name",
"summary": "summary",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a639e-ae18-79b9-8ff1-32d93c4802aa",
"created_at": "2025-11-08T13:18:55.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/13c0tXh2vK0",
"url": "http://pasture-one-actor/object/13c0tXh2vK0",
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"favourited": false,
"reblogged": false,
"muted": false,
"bookmarked": false,
"pinned": false,
"content": "only summary",
"reblog": null,
"quote_id": null,
"quote": null,
"application": null,
"account": {
"id": "019a639c-17b5-7c5f-857b-ea23de5bacce",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-08T13:16:05.368Z",
"note": "",
"url": "http://pasture-one-actor/actor",
"avatar": "http://hollo/image/avatars/original/missing.png",
"avatar_static": "http://hollo/image/avatars/original/missing.png",
"header": "http://hollo/image/headers/original/missing.png",
"header_static": "http://hollo/image/headers/original/missing.png",
"followers_count": 0,
"following_count": 0,
"statuses_count": 0,
"moved": null,
"last_status_at": null,
"emojis": [],
"fields": []
},
"media_attachments": [
{
"id": "019a639e-b149-76c8-a5ec-90bed073b1b3",
"type": "image",
"url": "http://pasture-one-actor/images/87c89873-e30b-4a71-b5dd-bf70cac1b10f.png",
"preview_url": "http://pasture-one-actor/images/87c89873-e30b-4a71-b5dd-bf70cac1b10f.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": "summary",
"blurhash": null
}
],
"mentions": [],
"tags": [],
"card": null,
"emojis": [],
"emoji_reactions": [],
"poll": null,
"filtered": null
}
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": [
"http://hollo/@john",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/nkBbjKxByw0",
"published": "2025-11-08T13:18:56Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/object/99oj_7nMivA",
"published": "2025-11-08T13:18:56Z",
"content": "only content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/2a498397-bb81-4526-9e1f-bffc671bc74e.png",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a639e-b200-756a-9a90-dea4ba854175",
"created_at": "2025-11-08T13:18:56.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/99oj_7nMivA",
"url": "http://pasture-one-actor/object/99oj_7nMivA",
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"favourited": false,
"reblogged": false,
"muted": false,
"bookmarked": false,
"pinned": false,
"content": "only content",
"reblog": null,
"quote_id": null,
"quote": null,
"application": null,
"account": {
"id": "019a639c-17b5-7c5f-857b-ea23de5bacce",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-08T13:16:05.368Z",
"note": "",
"url": "http://pasture-one-actor/actor",
"avatar": "http://hollo/image/avatars/original/missing.png",
"avatar_static": "http://hollo/image/avatars/original/missing.png",
"header": "http://hollo/image/headers/original/missing.png",
"header_static": "http://hollo/image/headers/original/missing.png",
"followers_count": 0,
"following_count": 0,
"statuses_count": 0,
"moved": null,
"last_status_at": null,
"emojis": [],
"fields": []
},
"media_attachments": [
{
"id": "019a639e-b3fb-793c-87db-4af6bdd2d567",
"type": "image",
"url": "http://pasture-one-actor/images/2a498397-bb81-4526-9e1f-bffc671bc74e.png",
"preview_url": "http://pasture-one-actor/images/2a498397-bb81-4526-9e1f-bffc671bc74e.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
}
],
"mentions": [],
"tags": [],
"card": null,
"emojis": [],
"emoji_reactions": [],
"poll": null,
"filtered": null
}
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": [
"http://hollo/@john",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/znPJhGMkMGY",
"published": "2025-11-08T13:18:57Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/object/zek_5waIAz4",
"published": "2025-11-08T13:18:57Z",
"content": "no comment in attachment; reused image",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
],
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a639e-b5e8-73f4-b5bd-3ecbf7cd1fb0",
"created_at": "2025-11-08T13:18:57.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/zek_5waIAz4",
"url": "http://pasture-one-actor/object/zek_5waIAz4",
"replies_count": 0,
"reblogs_count": 0,
"favourites_count": 0,
"favourited": false,
"reblogged": false,
"muted": false,
"bookmarked": false,
"pinned": false,
"content": "no comment in attachment; reused image",
"reblog": null,
"quote_id": null,
"quote": null,
"application": null,
"account": {
"id": "019a639c-17b5-7c5f-857b-ea23de5bacce",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-08T13:16:05.368Z",
"note": "",
"url": "http://pasture-one-actor/actor",
"avatar": "http://hollo/image/avatars/original/missing.png",
"avatar_static": "http://hollo/image/avatars/original/missing.png",
"header": "http://hollo/image/headers/original/missing.png",
"header_static": "http://hollo/image/headers/original/missing.png",
"followers_count": 0,
"following_count": 0,
"statuses_count": 0,
"moved": null,
"last_status_at": null,
"emojis": [],
"fields": []
},
"media_attachments": [
{
"id": "019a639e-b67c-7448-9dfa-30549f7f5109",
"type": "image",
"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": null,
"blurhash": null
}
],
"mentions": [],
"tags": [],
"card": null,
"emojis": [],
"emoji_reactions": [],
"poll": null,
"filtered": null
}