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/9kN6zXNwtX0",
"published": "2025-11-21T14:14:50Z",
"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/F7nqM9nKMMg",
"published": "2025-11-21T14:14:50Z",
"content": "no description",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/a4f3ebae-17f0-40d6-991a-0f4fac4483d4.png"
}
}
}
mitra
{
"id": "019aa6c4-9278-2b1f-2a3b-bd213554e27f",
"uri": "http://pasture-one-actor/object/F7nqM9nKMMg",
"url": "http://pasture-one-actor/object/F7nqM9nKMMg",
"created_at": "2025-11-21T14:14:50.000Z",
"edited_at": null,
"account": {
"id": "019aa6c2-1ffd-aa0d-ee0c-cce05fc8f170",
"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": "2025-11-21T14:12:11.389Z",
"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,
"discoverable": true,
"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": "019aa6c4-9274-423f-b0b4-46dfc3f72758",
"type": "image",
"url": "http://mitra/media/9f0f82db9c26b3f30aaba5de78ea082ef2e2cb1f8b0a560f91f7fd0b1bc290d9.png",
"preview_url": "http://mitra/media/9f0f82db9c26b3f30aaba5de78ea082ef2e2cb1f8b0a560f91f7fd0b1bc290d9.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "019aa6c0-e4be-204c-88e2-876d15258046",
"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/FD22EobOrH0",
"published": "2025-11-21T14:14:52Z",
"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/Lan0fP4nRPM",
"published": "2025-11-21T14:14:52Z",
"content": "name, summary and content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/a145a424-351a-45e1-9e0a-526a114e4508.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
mitra
{
"id": "019aa6c4-985b-6b78-8859-c8e476b85fb3",
"uri": "http://pasture-one-actor/object/Lan0fP4nRPM",
"url": "http://pasture-one-actor/object/Lan0fP4nRPM",
"created_at": "2025-11-21T14:14:52.000Z",
"edited_at": null,
"account": {
"id": "019aa6c2-1ffd-aa0d-ee0c-cce05fc8f170",
"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": "2025-11-21T14:12:11.389Z",
"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,
"discoverable": true,
"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": "019aa6c4-9857-edb1-a17d-eacd8675138f",
"type": "image",
"url": "http://mitra/media/2c23daaebc25c117f17c79fac7996b0d0bc9ef6927287860b8dfb9a047c80992.png",
"preview_url": "http://mitra/media/2c23daaebc25c117f17c79fac7996b0d0bc9ef6927287860b8dfb9a047c80992.png",
"description": "name"
}
],
"quote": null,
"mentions": [
{
"id": "019aa6c0-e4be-204c-88e2-876d15258046",
"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/ppD-B34aWHc",
"published": "2025-11-21T14:14:53Z",
"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/gOnhFkJ3yrE",
"published": "2025-11-21T14:14:53Z",
"content": "only name",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"name": "name",
"imageType": "image/jpeg"
}
]
}
}
mitra
{
"id": "019aa6c4-9e67-4a97-1638-dd04e89d5bdc",
"uri": "http://pasture-one-actor/object/gOnhFkJ3yrE",
"url": "http://pasture-one-actor/object/gOnhFkJ3yrE",
"created_at": "2025-11-21T14:14:53.000Z",
"edited_at": null,
"account": {
"id": "019aa6c2-1ffd-aa0d-ee0c-cce05fc8f170",
"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": "2025-11-21T14:12:11.389Z",
"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,
"discoverable": true,
"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": "019aa6c4-9e62-6de1-44c2-0567c8900c2c",
"type": "image",
"url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"description": "name"
}
],
"quote": null,
"mentions": [
{
"id": "019aa6c0-e4be-204c-88e2-876d15258046",
"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/OdUqTkfU-XE",
"published": "2025-11-21T14:14:55Z",
"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/7lfWpEmSBoA",
"published": "2025-11-21T14:14:55Z",
"content": "only summary",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/5aeed9fd-13b2-4da4-a814-e3036625bd7d.png",
"summary": "summary"
}
}
}
mitra
{
"id": "019aa6c4-a42e-4eaf-c07a-b48fbd01b95d",
"uri": "http://pasture-one-actor/object/7lfWpEmSBoA",
"url": "http://pasture-one-actor/object/7lfWpEmSBoA",
"created_at": "2025-11-21T14:14:55.000Z",
"edited_at": null,
"account": {
"id": "019aa6c2-1ffd-aa0d-ee0c-cce05fc8f170",
"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": "2025-11-21T14:12:11.389Z",
"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,
"discoverable": true,
"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": "019aa6c4-a428-133a-41da-599127adca76",
"type": "image",
"url": "http://mitra/media/169acab48917ca651f39a264cc5524e1e858004187deed6ca1e3d5338b29b689.png",
"preview_url": "http://mitra/media/169acab48917ca651f39a264cc5524e1e858004187deed6ca1e3d5338b29b689.png",
"description": "summary"
}
],
"quote": null,
"mentions": [
{
"id": "019aa6c0-e4be-204c-88e2-876d15258046",
"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/s6mOkY2ZZUA",
"published": "2025-11-21T14:14:56Z",
"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/_CSMPr-aP3o",
"published": "2025-11-21T14:14:56Z",
"content": "only content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/8d242851-3945-4e7e-a7a5-f19c809fa808.png",
"content": "content"
}
}
}
mitra
{
"id": "019aa6c4-a9e8-bb2e-5878-356b1e014494",
"uri": "http://pasture-one-actor/object/_CSMPr-aP3o",
"url": "http://pasture-one-actor/object/_CSMPr-aP3o",
"created_at": "2025-11-21T14:14:56.000Z",
"edited_at": null,
"account": {
"id": "019aa6c2-1ffd-aa0d-ee0c-cce05fc8f170",
"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": "2025-11-21T14:12:11.389Z",
"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,
"discoverable": true,
"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": "019aa6c4-a9e5-5da8-5650-eddcb452855a",
"type": "image",
"url": "http://mitra/media/4135b4c97c03c626b561cf464a16cb59a8055bdb01d0a520621c7e6908b0123f.png",
"preview_url": "http://mitra/media/4135b4c97c03c626b561cf464a16cb59a8055bdb01d0a520621c7e6908b0123f.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "019aa6c0-e4be-204c-88e2-876d15258046",
"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/So5ISRRFCd0",
"published": "2025-11-21T14:14:58Z",
"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/UpcBayoDs2U",
"published": "2025-11-21T14:14:58Z",
"content": "no comment in attachment; reused image",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
]
}
}
mitra
{
"id": "019aa6c4-afc8-cee4-8fb1-70e17ddd71cf",
"uri": "http://pasture-one-actor/object/UpcBayoDs2U",
"url": "http://pasture-one-actor/object/UpcBayoDs2U",
"created_at": "2025-11-21T14:14:58.000Z",
"edited_at": null,
"account": {
"id": "019aa6c2-1ffd-aa0d-ee0c-cce05fc8f170",
"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": "2025-11-21T14:12:11.389Z",
"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,
"discoverable": true,
"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": "019aa6c4-afc5-c47b-e207-70e014ed512f",
"type": "image",
"url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "019aa6c0-e4be-204c-88e2-876d15258046",
"username": "admin",
"acct": "admin",
"url": "http://mitra/users/admin"
}
],
"tags": [],
"emojis": [],
"favourited": false,
"reblogged": false,
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