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://hollo/@john"
],
"id": "http://pasture-one-actor/activity/RqLAIbYne1Q",
"published": "2025-11-12T07:37:07Z",
"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/SAJWDPFRXXQ",
"published": "2025-11-12T07:37:07Z",
"content": "no description",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/f0679456-5a27-4f20-b854-61ca6f0f480e.png"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a76ff-30b8-792e-a9b9-92e67da71a66",
"created_at": "2025-11-12T07:37:07.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/SAJWDPFRXXQ",
"url": "http://pasture-one-actor/object/SAJWDPFRXXQ",
"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": "019a76fc-d8e4-7177-8f15-d534a3fa54ed",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-12T07:34:33.392Z",
"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": "019a76ff-32f1-7d9f-bcfb-0c02f687c65f",
"type": "image",
"url": "http://pasture-one-actor/images/f0679456-5a27-4f20-b854-61ca6f0f480e.png",
"preview_url": "http://pasture-one-actor/images/f0679456-5a27-4f20-b854-61ca6f0f480e.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": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/activity/eCGKP1yoAxo",
"published": "2025-11-12T07:37:08Z",
"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/keLRBGaENB0",
"published": "2025-11-12T07:37:08Z",
"content": "name, summary and content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/e9fdc351-aad6-42a5-a5cf-781bf5306086.png",
"name": "name",
"summary": "summary",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a76ff-34a0-7501-898e-ee511cfcb61a",
"created_at": "2025-11-12T07:37:08.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/keLRBGaENB0",
"url": "http://pasture-one-actor/object/keLRBGaENB0",
"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": "019a76fc-d8e4-7177-8f15-d534a3fa54ed",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-12T07:34:33.392Z",
"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": "019a76ff-3555-71dd-8c5a-a43a921bb7da",
"type": "image",
"url": "http://pasture-one-actor/images/e9fdc351-aad6-42a5-a5cf-781bf5306086.png",
"preview_url": "http://pasture-one-actor/images/e9fdc351-aad6-42a5-a5cf-781bf5306086.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": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/activity/2tEMH7_XEXw",
"published": "2025-11-12T07:37:08Z",
"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/7NFRBt3JXfI",
"published": "2025-11-12T07:37:08Z",
"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": "019a76ff-34a0-7501-898e-ee514abd1132",
"created_at": "2025-11-12T07:37:08.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/7NFRBt3JXfI",
"url": "http://pasture-one-actor/object/7NFRBt3JXfI",
"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": "019a76fc-d8e4-7177-8f15-d534a3fa54ed",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-12T07:34:33.392Z",
"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": "019a76ff-37cc-7ddf-be3e-0de43ff68644",
"type": "text",
"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": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/activity/croS_JWTKik",
"published": "2025-11-12T07:37:09Z",
"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/UrBbuQzKN54",
"published": "2025-11-12T07:37:09Z",
"content": "only summary",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/a8aa6bd0-83a6-45c7-80a0-80bb1857385f.png",
"name": "name",
"summary": "summary",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a76ff-3888-7df3-a7df-5e67bcaafab5",
"created_at": "2025-11-12T07:37:09.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/UrBbuQzKN54",
"url": "http://pasture-one-actor/object/UrBbuQzKN54",
"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": "019a76fc-d8e4-7177-8f15-d534a3fa54ed",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-12T07:34:33.392Z",
"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": "019a76ff-3a42-7325-9ba5-84744c3495ea",
"type": "image",
"url": "http://pasture-one-actor/images/a8aa6bd0-83a6-45c7-80a0-80bb1857385f.png",
"preview_url": "http://pasture-one-actor/images/a8aa6bd0-83a6-45c7-80a0-80bb1857385f.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": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/activity/fe4VTHphurs",
"published": "2025-11-12T07:37:09Z",
"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/nMDfarvXkV4",
"published": "2025-11-12T07:37:09Z",
"content": "only content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/73ffa436-b01a-4c46-82ab-f9e39aff2b02.png",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://hollo/@john"
}
]
}
}
hollo
{
"id": "019a76ff-3888-7df3-a7df-5e68915223d7",
"created_at": "2025-11-12T07:37:09.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/nMDfarvXkV4",
"url": "http://pasture-one-actor/object/nMDfarvXkV4",
"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": "019a76fc-d8e4-7177-8f15-d534a3fa54ed",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-12T07:34:33.392Z",
"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": "019a76ff-3c8d-7ef7-8466-7faca59653f0",
"type": "image",
"url": "http://pasture-one-actor/images/73ffa436-b01a-4c46-82ab-f9e39aff2b02.png",
"preview_url": "http://pasture-one-actor/images/73ffa436-b01a-4c46-82ab-f9e39aff2b02.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": [
"https://www.w3.org/ns/activitystreams#Public",
"http://hollo/@john"
],
"id": "http://pasture-one-actor/activity/l8hdsxpCfKg",
"published": "2025-11-12T07:37:10Z",
"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/3HkzPYfznbQ",
"published": "2025-11-12T07:37:10Z",
"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": "019a76ff-3c70-7190-b500-ee019cc25e04",
"created_at": "2025-11-12T07:37:10.000Z",
"in_reply_to_id": null,
"sensitive": false,
"spoiler_text": "",
"visibility": "public",
"language": null,
"uri": "http://pasture-one-actor/object/3HkzPYfznbQ",
"url": "http://pasture-one-actor/object/3HkzPYfznbQ",
"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": "019a76fc-d8e4-7177-8f15-d534a3fa54ed",
"username": "actor",
"acct": "actor@pasture-one-actor",
"display_name": "Test Actor",
"locked": false,
"bot": false,
"created_at": "2025-11-12T07:34:33.392Z",
"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": "019a76ff-3edf-7a9a-8eb3-0a71ecf6eb41",
"type": "text",
"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
}