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/4e998jGT-OM",
"published": "2025-11-21T13:14:55Z",
"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/wyH7hZy6fhk",
"published": "2025-11-21T13:14:55Z",
"content": "no description",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/56397de0-389b-4133-88de-9772aedd7cd3.png"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019aa68d-b098-7610-b060-c5831d35187e",
"created_at": "2025-11-21T13:14:55.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/wyH7hZy6fhk",
"url": "http://pasture-one-actor/object/wyH7hZy6fhk",
"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": "019aa68b-686a-74fd-b66d-cf29db1455ff",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-21T13:12:25.394Z",
"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": "019aa68d-b4b6-7686-ad69-a4e9f88609e2",
"type": "image",
"url": "http://pasture-one-actor/images/56397de0-389b-4133-88de-9772aedd7cd3.png",
"preview_url": "http://pasture-one-actor/images/56397de0-389b-4133-88de-9772aedd7cd3.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/9b3Phes0Y6A",
"published": "2025-11-21T13:14:56Z",
"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/ipdl00dEOJU",
"published": "2025-11-21T13:14:56Z",
"content": "name, summary and content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/dedc0332-6dfe-4d95-b259-ebf94b1db29e.png",
"name": "name",
"summary": "summary",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019aa68d-b480-735a-b619-be57e9f91cb6",
"created_at": "2025-11-21T13:14:56.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/ipdl00dEOJU",
"url": "http://pasture-one-actor/object/ipdl00dEOJU",
"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": "019aa68b-686a-74fd-b66d-cf29db1455ff",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-21T13:12:25.394Z",
"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": "019aa68d-b72a-7315-9390-7a78e77161c8",
"type": "image",
"url": "http://pasture-one-actor/images/dedc0332-6dfe-4d95-b259-ebf94b1db29e.png",
"preview_url": "http://pasture-one-actor/images/dedc0332-6dfe-4d95-b259-ebf94b1db29e.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/uD0woYCs4Jc",
"published": "2025-11-21T13:14:57Z",
"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/m-H3VqoKDZQ",
"published": "2025-11-21T13:14:57Z",
"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": "019aa68d-b868-729b-92d7-d17a214feec6",
"created_at": "2025-11-21T13:14:57.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/m-H3VqoKDZQ",
"url": "http://pasture-one-actor/object/m-H3VqoKDZQ",
"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": "019aa68b-686a-74fd-b66d-cf29db1455ff",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-21T13:12:25.394Z",
"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": "019aa68d-b9af-7113-b8ad-97ce02c7c4bb",
"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/K-_0aIIbEEs",
"published": "2025-11-21T13:14:57Z",
"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/Kn8Z-eeE9kE",
"published": "2025-11-21T13:14:57Z",
"content": "only summary",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/f5fbb170-4404-4683-862c-e0bc5f9d4391.png",
"summary": "summary"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019aa68d-b868-729b-92d7-d17ad419d6c4",
"created_at": "2025-11-21T13:14:57.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/Kn8Z-eeE9kE",
"url": "http://pasture-one-actor/object/Kn8Z-eeE9kE",
"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": "019aa68b-686a-74fd-b66d-cf29db1455ff",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-21T13:12:25.394Z",
"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": "019aa68d-bbfe-7356-9dba-9ad8787cd9f5",
"type": "image",
"url": "http://pasture-one-actor/images/f5fbb170-4404-4683-862c-e0bc5f9d4391.png",
"preview_url": "http://pasture-one-actor/images/f5fbb170-4404-4683-862c-e0bc5f9d4391.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/88hpt52zpro",
"published": "2025-11-21T13:14:58Z",
"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/MpkHkKhbZDc",
"published": "2025-11-21T13:14:58Z",
"content": "only content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/8cabfa48-13a9-4c73-9a30-82ca49188970.png",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019aa68d-bc50-70ab-80de-03352bce350f",
"created_at": "2025-11-21T13:14:58.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/MpkHkKhbZDc",
"url": "http://pasture-one-actor/object/MpkHkKhbZDc",
"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": "019aa68b-686a-74fd-b66d-cf29db1455ff",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-21T13:12:25.394Z",
"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": "019aa68d-be73-7de6-b709-2056547f26d2",
"type": "image",
"url": "http://pasture-one-actor/images/8cabfa48-13a9-4c73-9a30-82ca49188970.png",
"preview_url": "http://pasture-one-actor/images/8cabfa48-13a9-4c73-9a30-82ca49188970.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/Mh7NcYeMIc8",
"published": "2025-11-21T13:14:59Z",
"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/79B_qrrV_JU",
"published": "2025-11-21T13:14:59Z",
"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": "019aa68d-c038-7dd9-985a-1a19687ba7c2",
"created_at": "2025-11-21T13:14:59.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/79B_qrrV_JU",
"url": "http://pasture-one-actor/object/79B_qrrV_JU",
"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": "019aa68b-686a-74fd-b66d-cf29db1455ff",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-21T13:12:25.394Z",
"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": "019aa68d-c0e1-73bf-8484-aed12c26c892",
"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
}