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://pyfedi.local/c/pie",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/MpQwVtKzV1w",
"published": "2025-09-14T08:53:55Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://pyfedi.local/c/pie"
],
"id": "http://pasture-one-actor/object/3PDme7H7uX0",
"published": "2025-09-14T08:53:55Z",
"content": "no description",
"attachment": {
"type": "Document",
"url": "http://pasture-one-actor/images/100.png"
},
"tag": [
{
"type": "Mention",
"href": "http://pyfedi.local/c/pie"
}
]
}
}
pyfedi
{
"id": 64,
"user_id": 2,
"community_id": 1,
"title": "[Microblog] no description",
"deleted": false,
"nsfw": false,
"sticky": false,
"published": "2025-09-14T08:53:56.015939Z",
"ap_id": "http://pasture-one-actor/object/3PDme7H7uX0",
"local": false,
"language_id": 2,
"removed": false,
"locked": false,
"body": "no description",
"url": "http://pasture-one-actor/images/100.png",
"thumbnail_url": "http://pasture-one-actor/images/100.png",
"small_thumbnail_url": "http://pasture-one-actor/images/100.png"
}
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://pyfedi.local/c/pie",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/SBDhPfi7Bcs",
"published": "2025-09-14T08:53:56Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://pyfedi.local/c/pie"
],
"id": "http://pasture-one-actor/object/ImY4d2WDkUk",
"published": "2025-09-14T08:53:56Z",
"content": "name and summary",
"attachment": {
"type": "Document",
"url": "http://pasture-one-actor/images/100.png",
"name": "name",
"summary": "summary",
"content": "content"
},
"tag": [
{
"type": "Mention",
"href": "http://pyfedi.local/c/pie"
}
]
}
}
pyfedi
{
"id": 65,
"user_id": 2,
"community_id": 1,
"title": "[Microblog] name and summary",
"deleted": false,
"nsfw": false,
"sticky": false,
"published": "2025-09-14T08:53:56.819251Z",
"ap_id": "http://pasture-one-actor/object/ImY4d2WDkUk",
"local": false,
"language_id": 2,
"removed": false,
"locked": false,
"body": "name and summary",
"url": "http://pasture-one-actor/images/100.png",
"thumbnail_url": "http://pasture-one-actor/images/100.png",
"small_thumbnail_url": "http://pasture-one-actor/images/100.png"
}
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://pyfedi.local/c/pie",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/vsq6Bt3wG6w",
"published": "2025-09-14T08:53:57Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://pyfedi.local/c/pie"
],
"id": "http://pasture-one-actor/object/LnLFe61_6Ns",
"published": "2025-09-14T08:53:57Z",
"content": "only name",
"attachment": [
{
"type": "Document",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"name": "name",
"imageType": "image/jpeg"
}
],
"tag": [
{
"type": "Mention",
"href": "http://pyfedi.local/c/pie"
}
]
}
}
pyfedi
{
"id": 66,
"user_id": 2,
"community_id": 1,
"title": "(content in post body)",
"deleted": false,
"nsfw": false,
"sticky": false,
"published": "2025-09-14T08:53:57.568491Z",
"ap_id": "http://pasture-one-actor/object/LnLFe61_6Ns",
"local": false,
"language_id": 2,
"removed": false,
"locked": false,
"body": "only name",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"thumbnail_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"small_thumbnail_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"alt_text": "name"
}
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://pyfedi.local/c/pie",
"https://www.w3.org/ns/activitystreams#Public"
],
"id": "http://pasture-one-actor/activity/VykSwQatNrY",
"published": "2025-09-14T08:53:58Z",
"object": {
"type": "Note",
"attributedTo": "http://pasture-one-actor/actor",
"to": [
"https://www.w3.org/ns/activitystreams#Public",
"http://pyfedi.local/c/pie"
],
"id": "http://pasture-one-actor/object/uoqz1vXBqyo",
"published": "2025-09-14T08:53:58Z",
"content": "no comment in attachment",
"attachment": [
{
"type": "Document",
"url": "http://pasture-one-actor/assets/FediverseLogo.png"
}
],
"tag": [
{
"type": "Mention",
"href": "http://pyfedi.local/c/pie"
}
]
}
}
pyfedi
{
"id": 67,
"user_id": 2,
"community_id": 1,
"title": "no comment in attachment",
"deleted": false,
"nsfw": false,
"sticky": false,
"published": "2025-09-14T08:53:58.360439Z",
"ap_id": "http://pasture-one-actor/object/uoqz1vXBqyo",
"local": false,
"language_id": 2,
"removed": false,
"locked": false,
"body": "no comment in attachment",
"url": "http://pasture-one-actor/assets/FediverseLogo.png",
"thumbnail_url": "http://pasture-one-actor/assets/FediverseLogo.png",
"small_thumbnail_url": "http://pasture-one-actor/assets/FediverseLogo.png"
}