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://mitra/users/admin",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/1NCnauD85kw",
"published": "2025-10-11T09:47:41Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://mitra/users/admin"
],
"id": "http://pasture-one-actor/object/yrWfUP0dvJ8",
"published": "2025-10-11T09:47:41Z",
"content": "no description",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/bab6d2ad-b10c-45b3-9bae-5390e67db3a4.png"
}
}
}
mitra
{
"id": "0199d2ab-3f49-16c4-8b1f-d7693b07f434",
"uri": "http://pasture-one-actor/object/yrWfUP0dvJ8",
"url": "http://pasture-one-actor/object/yrWfUP0dvJ8",
"created_at": "2025-10-11T09:47:41.000Z",
"edited_at": null,
"account": {
"id": "0199d2a8-cc7f-d944-db37-dce1869ca342",
"username": "actor",
"acct": "actor@pasture-one-actor",
"actor_id": "http://pasture-one-actor/actor",
"url": "http://pasture-one-actor/actor",
"display_name": "Test Actor",
"created_at": "2025-10-11T09:45:01.823Z",
"note": "",
"avatar": "http://mitra/api/v1/accounts/identicon?input=http://pasture-one-actor/actor",
"header": "http://mitra/api/v1/accounts/identicon",
"locked": false,
"mention_policy": "none",
"bot": false,
"identity_proofs": [],
"payment_options": [],
"fields": [],
"emojis": [],
"followers_count": 0,
"following_count": 0,
"subscribers_count": 0,
"statuses_count": 71,
"source": null,
"role": null,
"authentication_methods": null,
"client_config": null
},
"content": "no description",
"language": null,
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"visibility": "public",
"sensitive": false,
"spoiler_text": "",
"pinned": false,
"replies_count": 0,
"favourites_count": 0,
"reblogs_count": 0,
"poll": null,
"media_attachments": [
{
"id": "0199d2ab-3f44-68f5-bcaa-1c67d65624df",
"type": "image",
"url": "http://mitra/media/9d60c900236c43e246b975dffe3ee2aadf904d96de93d5b237b0733a0dcfb2cc.png",
"preview_url": "http://mitra/media/9d60c900236c43e246b975dffe3ee2aadf904d96de93d5b237b0733a0dcfb2cc.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "0199d2a7-629a-ea91-e871-93a9f6f977b1",
"username": "admin",
"acct": "admin",
"url": "http://mitra/users/admin"
}
],
"tags": [],
"emojis": [],
"favourited": false,
"reblogged": false,
"bookmarked": false,
"pleroma": {
"emoji_reactions": [],
"in_reply_to_account_acct": null,
"parent_visible": true,
"quote": null,
"quote_visible": true
},
"hidden": false,
"ipfs_cid": null,
"links": []
}
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://mitra/users/admin",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/nKK80u70ERg",
"published": "2025-10-11T09:47:42Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://mitra/users/admin"
],
"id": "http://pasture-one-actor/object/9FrWVlmj5YE",
"published": "2025-10-11T09:47:42Z",
"content": "name, summary and content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/62a231a7-078d-4a93-9431-be42fdf9eb7f.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
mitra
{
"id": "0199d2ab-4523-dd2a-3500-6e81c60ffb44",
"uri": "http://pasture-one-actor/object/9FrWVlmj5YE",
"url": "http://pasture-one-actor/object/9FrWVlmj5YE",
"created_at": "2025-10-11T09:47:42.000Z",
"edited_at": null,
"account": {
"id": "0199d2a8-cc7f-d944-db37-dce1869ca342",
"username": "actor",
"acct": "actor@pasture-one-actor",
"actor_id": "http://pasture-one-actor/actor",
"url": "http://pasture-one-actor/actor",
"display_name": "Test Actor",
"created_at": "2025-10-11T09:45:01.823Z",
"note": "",
"avatar": "http://mitra/api/v1/accounts/identicon?input=http://pasture-one-actor/actor",
"header": "http://mitra/api/v1/accounts/identicon",
"locked": false,
"mention_policy": "none",
"bot": false,
"identity_proofs": [],
"payment_options": [],
"fields": [],
"emojis": [],
"followers_count": 0,
"following_count": 0,
"subscribers_count": 0,
"statuses_count": 72,
"source": null,
"role": null,
"authentication_methods": null,
"client_config": null
},
"content": "name, summary and content",
"language": null,
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"visibility": "public",
"sensitive": false,
"spoiler_text": "",
"pinned": false,
"replies_count": 0,
"favourites_count": 0,
"reblogs_count": 0,
"poll": null,
"media_attachments": [
{
"id": "0199d2ab-451d-8792-6ad2-3a2087ab371f",
"type": "image",
"url": "http://mitra/media/cf0978dd84b083d2e7408a26ca88a3a9d4d445fe15fb938548fcbe4d1f077d70.png",
"preview_url": "http://mitra/media/cf0978dd84b083d2e7408a26ca88a3a9d4d445fe15fb938548fcbe4d1f077d70.png",
"description": "name"
}
],
"quote": null,
"mentions": [
{
"id": "0199d2a7-629a-ea91-e871-93a9f6f977b1",
"username": "admin",
"acct": "admin",
"url": "http://mitra/users/admin"
}
],
"tags": [],
"emojis": [],
"favourited": false,
"reblogged": false,
"bookmarked": false,
"pleroma": {
"emoji_reactions": [],
"in_reply_to_account_acct": null,
"parent_visible": true,
"quote": null,
"quote_visible": true
},
"hidden": false,
"ipfs_cid": null,
"links": []
}
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://mitra/users/admin",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/BDdcSlJslLY",
"published": "2025-10-11T09:47:43Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://mitra/users/admin"
],
"id": "http://pasture-one-actor/object/363MmifxmCU",
"published": "2025-10-11T09:47:43Z",
"content": "only name",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"name": "name",
"imageType": "image/jpeg"
}
]
}
}
mitra
{
"id": "0199d2ab-4b0c-9c3a-9e58-2ef06fdcbb1e",
"uri": "http://pasture-one-actor/object/363MmifxmCU",
"url": "http://pasture-one-actor/object/363MmifxmCU",
"created_at": "2025-10-11T09:47:43.000Z",
"edited_at": null,
"account": {
"id": "0199d2a8-cc7f-d944-db37-dce1869ca342",
"username": "actor",
"acct": "actor@pasture-one-actor",
"actor_id": "http://pasture-one-actor/actor",
"url": "http://pasture-one-actor/actor",
"display_name": "Test Actor",
"created_at": "2025-10-11T09:45:01.823Z",
"note": "",
"avatar": "http://mitra/api/v1/accounts/identicon?input=http://pasture-one-actor/actor",
"header": "http://mitra/api/v1/accounts/identicon",
"locked": false,
"mention_policy": "none",
"bot": false,
"identity_proofs": [],
"payment_options": [],
"fields": [],
"emojis": [],
"followers_count": 0,
"following_count": 0,
"subscribers_count": 0,
"statuses_count": 73,
"source": null,
"role": null,
"authentication_methods": null,
"client_config": null
},
"content": "only name",
"language": null,
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"visibility": "public",
"sensitive": false,
"spoiler_text": "",
"pinned": false,
"replies_count": 0,
"favourites_count": 0,
"reblogs_count": 0,
"poll": null,
"media_attachments": [
{
"id": "0199d2ab-4b07-920c-47be-52a66ef18871",
"type": "image",
"url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"description": "name"
}
],
"quote": null,
"mentions": [
{
"id": "0199d2a7-629a-ea91-e871-93a9f6f977b1",
"username": "admin",
"acct": "admin",
"url": "http://mitra/users/admin"
}
],
"tags": [],
"emojis": [],
"favourited": false,
"reblogged": false,
"bookmarked": false,
"pleroma": {
"emoji_reactions": [],
"in_reply_to_account_acct": null,
"parent_visible": true,
"quote": null,
"quote_visible": true
},
"hidden": false,
"ipfs_cid": null,
"links": []
}
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://mitra/users/admin",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/jKM2Cu4fWGY",
"published": "2025-10-11T09:47:45Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://mitra/users/admin"
],
"id": "http://pasture-one-actor/object/W-awXosFyao",
"published": "2025-10-11T09:47:45Z",
"content": "only summary",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/9aee3d6f-8a39-4a53-84ed-329f02eb2420.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
mitra
{
"id": "0199d2ab-50bd-09f8-9189-e6d72a8a236a",
"uri": "http://pasture-one-actor/object/W-awXosFyao",
"url": "http://pasture-one-actor/object/W-awXosFyao",
"created_at": "2025-10-11T09:47:45.000Z",
"edited_at": null,
"account": {
"id": "0199d2a8-cc7f-d944-db37-dce1869ca342",
"username": "actor",
"acct": "actor@pasture-one-actor",
"actor_id": "http://pasture-one-actor/actor",
"url": "http://pasture-one-actor/actor",
"display_name": "Test Actor",
"created_at": "2025-10-11T09:45:01.823Z",
"note": "",
"avatar": "http://mitra/api/v1/accounts/identicon?input=http://pasture-one-actor/actor",
"header": "http://mitra/api/v1/accounts/identicon",
"locked": false,
"mention_policy": "none",
"bot": false,
"identity_proofs": [],
"payment_options": [],
"fields": [],
"emojis": [],
"followers_count": 0,
"following_count": 0,
"subscribers_count": 0,
"statuses_count": 74,
"source": null,
"role": null,
"authentication_methods": null,
"client_config": null
},
"content": "only summary",
"language": null,
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"visibility": "public",
"sensitive": false,
"spoiler_text": "",
"pinned": false,
"replies_count": 0,
"favourites_count": 0,
"reblogs_count": 0,
"poll": null,
"media_attachments": [
{
"id": "0199d2ab-50b9-d1dc-0238-19774dee3457",
"type": "image",
"url": "http://mitra/media/a8a1e022e5c13dd7fbfae55ab06a6bc8613a3fb038b20171fabc2498514c6d6f.png",
"preview_url": "http://mitra/media/a8a1e022e5c13dd7fbfae55ab06a6bc8613a3fb038b20171fabc2498514c6d6f.png",
"description": "name"
}
],
"quote": null,
"mentions": [
{
"id": "0199d2a7-629a-ea91-e871-93a9f6f977b1",
"username": "admin",
"acct": "admin",
"url": "http://mitra/users/admin"
}
],
"tags": [],
"emojis": [],
"favourited": false,
"reblogged": false,
"bookmarked": false,
"pleroma": {
"emoji_reactions": [],
"in_reply_to_account_acct": null,
"parent_visible": true,
"quote": null,
"quote_visible": true
},
"hidden": false,
"ipfs_cid": null,
"links": []
}
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://mitra/users/admin",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/yp1e2p079s4",
"published": "2025-10-11T09:47:47Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://mitra/users/admin"
],
"id": "http://pasture-one-actor/object/SDv3O7Euja4",
"published": "2025-10-11T09:47:47Z",
"content": "only content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/673fa07d-b7c1-497c-864b-40d0d1d3a480.png",
"content": "content"
}
}
}
mitra
{
"id": "0199d2ab-56a5-e9b8-3147-61dca19eb51b",
"uri": "http://pasture-one-actor/object/SDv3O7Euja4",
"url": "http://pasture-one-actor/object/SDv3O7Euja4",
"created_at": "2025-10-11T09:47:47.000Z",
"edited_at": null,
"account": {
"id": "0199d2a8-cc7f-d944-db37-dce1869ca342",
"username": "actor",
"acct": "actor@pasture-one-actor",
"actor_id": "http://pasture-one-actor/actor",
"url": "http://pasture-one-actor/actor",
"display_name": "Test Actor",
"created_at": "2025-10-11T09:45:01.823Z",
"note": "",
"avatar": "http://mitra/api/v1/accounts/identicon?input=http://pasture-one-actor/actor",
"header": "http://mitra/api/v1/accounts/identicon",
"locked": false,
"mention_policy": "none",
"bot": false,
"identity_proofs": [],
"payment_options": [],
"fields": [],
"emojis": [],
"followers_count": 0,
"following_count": 0,
"subscribers_count": 0,
"statuses_count": 75,
"source": null,
"role": null,
"authentication_methods": null,
"client_config": null
},
"content": "only content",
"language": null,
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"visibility": "public",
"sensitive": false,
"spoiler_text": "",
"pinned": false,
"replies_count": 0,
"favourites_count": 0,
"reblogs_count": 0,
"poll": null,
"media_attachments": [
{
"id": "0199d2ab-56a2-a8a1-ffff-29d727ed6870",
"type": "image",
"url": "http://mitra/media/d1f6ca071fbbd3da175024281ba12d822684f5777b0244ac42af11043cf94aab.png",
"preview_url": "http://mitra/media/d1f6ca071fbbd3da175024281ba12d822684f5777b0244ac42af11043cf94aab.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "0199d2a7-629a-ea91-e871-93a9f6f977b1",
"username": "admin",
"acct": "admin",
"url": "http://mitra/users/admin"
}
],
"tags": [],
"emojis": [],
"favourited": false,
"reblogged": false,
"bookmarked": false,
"pleroma": {
"emoji_reactions": [],
"in_reply_to_account_acct": null,
"parent_visible": true,
"quote": null,
"quote_visible": true
},
"hidden": false,
"ipfs_cid": null,
"links": []
}
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://mitra/users/admin",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/qAmedxa8A10",
"published": "2025-10-11T09:47:48Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://mitra/users/admin"
],
"id": "http://pasture-one-actor/object/87vH2_jOUas",
"published": "2025-10-11T09:47:48Z",
"content": "no comment in attachment; reused image",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
]
}
}
mitra
{
"id": "0199d2ab-5cbc-b711-07d6-85f67cfe7dc4",
"uri": "http://pasture-one-actor/object/87vH2_jOUas",
"url": "http://pasture-one-actor/object/87vH2_jOUas",
"created_at": "2025-10-11T09:47:48.000Z",
"edited_at": null,
"account": {
"id": "0199d2a8-cc7f-d944-db37-dce1869ca342",
"username": "actor",
"acct": "actor@pasture-one-actor",
"actor_id": "http://pasture-one-actor/actor",
"url": "http://pasture-one-actor/actor",
"display_name": "Test Actor",
"created_at": "2025-10-11T09:45:01.823Z",
"note": "",
"avatar": "http://mitra/api/v1/accounts/identicon?input=http://pasture-one-actor/actor",
"header": "http://mitra/api/v1/accounts/identicon",
"locked": false,
"mention_policy": "none",
"bot": false,
"identity_proofs": [],
"payment_options": [],
"fields": [],
"emojis": [],
"followers_count": 0,
"following_count": 0,
"subscribers_count": 0,
"statuses_count": 76,
"source": null,
"role": null,
"authentication_methods": null,
"client_config": null
},
"content": "no comment in attachment; reused image",
"language": null,
"in_reply_to_id": null,
"in_reply_to_account_id": null,
"reblog": null,
"visibility": "public",
"sensitive": false,
"spoiler_text": "",
"pinned": false,
"replies_count": 0,
"favourites_count": 0,
"reblogs_count": 0,
"poll": null,
"media_attachments": [
{
"id": "0199d2ab-5cb4-6e07-01a0-56278221d089",
"type": "image",
"url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "0199d2a7-629a-ea91-e871-93a9f6f977b1",
"username": "admin",
"acct": "admin",
"url": "http://mitra/users/admin"
}
],
"tags": [],
"emojis": [],
"favourited": false,
"reblogged": false,
"bookmarked": false,
"pleroma": {
"emoji_reactions": [],
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