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/kvAm_Zktypo",
"published": "2025-10-28T11:08:43Z",
"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/hEbndkFR_dk",
"published": "2025-10-28T11:08:43Z",
"content": "no description",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/697ef205-71d7-4488-b8a8-3944dd86d660.png"
}
}
}
mitra
{
"id": "019a2a81-8e49-51be-6740-75755a1d0aa5",
"uri": "http://pasture-one-actor/object/hEbndkFR_dk",
"url": "http://pasture-one-actor/object/hEbndkFR_dk",
"created_at": "2025-10-28T11:08:43.000Z",
"edited_at": null,
"account": {
"id": "019a2a7f-17ff-0d36-2726-b3d2cd5016df",
"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": "2025-10-28T11:06:03.646Z",
"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": "019a2a81-8e45-e5a4-8170-ca5d74589cb8",
"type": "image",
"url": "http://mitra/media/93ce39141bd7dd29b3875f667c6dfc7278dea15402177f3e3583655caddf428f.png",
"preview_url": "http://mitra/media/93ce39141bd7dd29b3875f667c6dfc7278dea15402177f3e3583655caddf428f.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "019a2a7d-afbb-3557-1da7-96ba62336276",
"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/PjbIRV3e530",
"published": "2025-10-28T11:08:45Z",
"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/VrWfGcxH95M",
"published": "2025-10-28T11:08:45Z",
"content": "name, summary and content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/34512b21-fd72-45c5-a5a2-3a37aba95c20.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
mitra
{
"id": "019a2a81-9429-ff6c-d23f-42ed88380b0b",
"uri": "http://pasture-one-actor/object/VrWfGcxH95M",
"url": "http://pasture-one-actor/object/VrWfGcxH95M",
"created_at": "2025-10-28T11:08:45.000Z",
"edited_at": null,
"account": {
"id": "019a2a7f-17ff-0d36-2726-b3d2cd5016df",
"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": "2025-10-28T11:06:03.646Z",
"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": "019a2a81-9425-7245-e3e7-0bfbf9f8241c",
"type": "image",
"url": "http://mitra/media/1844b25b96d4873de636f2ba1961d6456bad393e6597a51edb8f80ef46d8ab83.png",
"preview_url": "http://mitra/media/1844b25b96d4873de636f2ba1961d6456bad393e6597a51edb8f80ef46d8ab83.png",
"description": "name"
}
],
"quote": null,
"mentions": [
{
"id": "019a2a7d-afbb-3557-1da7-96ba62336276",
"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/5ARyUsMnkUE",
"published": "2025-10-28T11:08:46Z",
"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/uPApDV2B8Hs",
"published": "2025-10-28T11:08:46Z",
"content": "only name",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"name": "name",
"imageType": "image/jpeg"
}
]
}
}
mitra
{
"id": "019a2a81-9a37-7f50-c13b-96e4d9f704ba",
"uri": "http://pasture-one-actor/object/uPApDV2B8Hs",
"url": "http://pasture-one-actor/object/uPApDV2B8Hs",
"created_at": "2025-10-28T11:08:46.000Z",
"edited_at": null,
"account": {
"id": "019a2a7f-17ff-0d36-2726-b3d2cd5016df",
"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": "2025-10-28T11:06:03.646Z",
"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": "019a2a81-9a30-cd10-7512-52ff69c03fff",
"type": "image",
"url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"description": "name"
}
],
"quote": null,
"mentions": [
{
"id": "019a2a7d-afbb-3557-1da7-96ba62336276",
"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/41A3rdKntQ8",
"published": "2025-10-28T11:08:48Z",
"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/q4tuguACw-Q",
"published": "2025-10-28T11:08:48Z",
"content": "only summary",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/87345665-2423-4ab0-881c-a4bbf338fbe3.png",
"name": "name",
"summary": "summary",
"content": "content"
}
}
}
mitra
{
"id": "019a2a81-9fdf-7b0a-19cb-6cfd66639b8e",
"uri": "http://pasture-one-actor/object/q4tuguACw-Q",
"url": "http://pasture-one-actor/object/q4tuguACw-Q",
"created_at": "2025-10-28T11:08:48.000Z",
"edited_at": null,
"account": {
"id": "019a2a7f-17ff-0d36-2726-b3d2cd5016df",
"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": "2025-10-28T11:06:03.646Z",
"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": "019a2a81-9fda-2143-8155-f7fe27ccdbca",
"type": "image",
"url": "http://mitra/media/112e3ab58dac23854ae04269a365532748bc7c28191be270d13c2f66b9247550.png",
"preview_url": "http://mitra/media/112e3ab58dac23854ae04269a365532748bc7c28191be270d13c2f66b9247550.png",
"description": "name"
}
],
"quote": null,
"mentions": [
{
"id": "019a2a7d-afbb-3557-1da7-96ba62336276",
"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/PiH_UR9QUcg",
"published": "2025-10-28T11:08:50Z",
"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/UqfgjlXrZNA",
"published": "2025-10-28T11:08:50Z",
"content": "only content",
"attachment": {
"type": "Image",
"url": "http://pasture-one-actor/images/d570fe5e-be98-468e-b36e-53aa4ef8ddd7.png",
"content": "content"
}
}
}
mitra
{
"id": "019a2a81-a5ae-4445-4af0-bd39cbab26da",
"uri": "http://pasture-one-actor/object/UqfgjlXrZNA",
"url": "http://pasture-one-actor/object/UqfgjlXrZNA",
"created_at": "2025-10-28T11:08:50.000Z",
"edited_at": null,
"account": {
"id": "019a2a7f-17ff-0d36-2726-b3d2cd5016df",
"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": "2025-10-28T11:06:03.646Z",
"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": "019a2a81-a5ab-a1c4-450b-b74d1b6360cc",
"type": "image",
"url": "http://mitra/media/63dcd90e98918c6aff2e4ff42e8167cf971855b41c73fd3fb6c804ff0ef13004.png",
"preview_url": "http://mitra/media/63dcd90e98918c6aff2e4ff42e8167cf971855b41c73fd3fb6c804ff0ef13004.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "019a2a7d-afbb-3557-1da7-96ba62336276",
"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/dBGVVMyFVLo",
"published": "2025-10-28T11:08:51Z",
"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/8GNWfRwewEY",
"published": "2025-10-28T11:08:51Z",
"content": "no comment in attachment; reused image",
"attachment": [
{
"type": "Image",
"url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
]
}
}
mitra
{
"id": "019a2a81-abc9-9e7f-91bf-a10b718049de",
"uri": "http://pasture-one-actor/object/8GNWfRwewEY",
"url": "http://pasture-one-actor/object/8GNWfRwewEY",
"created_at": "2025-10-28T11:08:51.000Z",
"edited_at": null,
"account": {
"id": "019a2a7f-17ff-0d36-2726-b3d2cd5016df",
"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": "2025-10-28T11:06:03.646Z",
"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": "019a2a81-abc1-f6d3-23ee-4f7539607ef9",
"type": "image",
"url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"preview_url": "http://mitra/media/2d7a61d31393a44edf2a30160cdd70b3582a4f97d5b550f8141dfee1641b4ae7.png",
"description": null
}
],
"quote": null,
"mentions": [
{
"id": "019a2a7d-afbb-3557-1da7-96ba62336276",
"username": "admin",
"acct": "admin",
"url": "http://mitra/users/admin"
}
],
"tags": [],
"emojis": [],
"favourited": false,
"reblogged": false,
"bookmarked": false,
"pleroma": {
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