Hashtags and JSON-LD

The examples here are various variations of creating the Hashtag element in the tag list. These variations can be useful in understanding how strict an application sees JSON-LD.

Hashtags are a good illustration of JSON-LD parsing as Hashtag is not part of the ActivityStreams vocabulary.

All examples except the first are questionable, and probably should not be used when publishing to the Fediverse. The examples marked with ⚠️ are expected to fail with a JSON-LD parser. The examples using as:Hashtag are expected to fail with a JSON only parser.

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://mastodon/users/hippo"
  ],
  "id": "http://pasture-one-actor/activity/Qi_pR-OX-kI",
  "published": "2025-09-06T13:40:24Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mastodon/users/hippo"
    ],
    "id": "http://pasture-one-actor/object/2URTQZ2mH1g",
    "published": "2025-09-06T13:40:24Z",
    "content": "text",
    "tag": {
      "type": "Hashtag",
      "name": "#test"
    }
  }
}

mastodon

{
  "id": "115157632588807534",
  "created_at": "2025-09-06T13:40:24.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/2URTQZ2mH1g",
  "url": "http://pasture-one-actor/object/2URTQZ2mH1g",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "edited_at": null,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "content": "text",
  "filtered": [],
  "reblog": null,
  "account": {
    "id": "115157631664406598",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "discoverable": false,
    "indexable": false,
    "group": false,
    "created_at": "2025-09-06T00:00:00.000Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "uri": "http://pasture-one-actor/actor",
    "avatar": "http://mastodon/avatars/original/missing.png",
    "avatar_static": "http://mastodon/avatars/original/missing.png",
    "header": "http://mastodon/headers/original/missing.png",
    "header_static": "http://mastodon/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 14,
    "last_status_at": "2025-09-06",
    "hide_collections": true,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [],
  "mentions": [],
  "tags": [
    {
      "name": "test",
      "url": "http://mastodon/tags/test"
    }
  ],
  "emojis": [],
  "quote": null,
  "card": null,
  "poll": 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://mastodon/users/hippo"
  ],
  "id": "http://pasture-one-actor/activity/SAJM5gUZBDQ",
  "published": "2025-09-06T13:40:25Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mastodon/users/hippo"
    ],
    "id": "http://pasture-one-actor/object/_aOkB8YKnNI",
    "published": "2025-09-06T13:40:25Z",
    "content": "using as:Hashtag",
    "tag": {
      "type": "as:Hashtag",
      "name": "#test"
    }
  }
}

mastodon

{
  "id": "115157632653450284",
  "created_at": "2025-09-06T13:40:25.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/_aOkB8YKnNI",
  "url": "http://pasture-one-actor/object/_aOkB8YKnNI",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "edited_at": null,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "content": "using as:Hashtag",
  "filtered": [],
  "reblog": null,
  "account": {
    "id": "115157631664406598",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "discoverable": false,
    "indexable": false,
    "group": false,
    "created_at": "2025-09-06T00:00:00.000Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "uri": "http://pasture-one-actor/actor",
    "avatar": "http://mastodon/avatars/original/missing.png",
    "avatar_static": "http://mastodon/avatars/original/missing.png",
    "header": "http://mastodon/headers/original/missing.png",
    "header_static": "http://mastodon/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 15,
    "last_status_at": "2025-09-06",
    "hide_collections": true,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [],
  "mentions": [],
  "tags": [],
  "emojis": [],
  "quote": null,
  "card": null,
  "poll": 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://mastodon/users/hippo"
  ],
  "id": "http://pasture-one-actor/activity/uts3F6-1F2M",
  "published": "2025-09-06T13:40:26Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mastodon/users/hippo"
    ],
    "id": "http://pasture-one-actor/object/cTKVUUsL3U0",
    "published": "2025-09-06T13:40:26Z",
    "content": "no type \u26a0\ufe0f ",
    "tag": {
      "name": "#test"
    }
  }
}

mastodon

{
  "id": "115157632745584585",
  "created_at": "2025-09-06T13:40:26.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/cTKVUUsL3U0",
  "url": "http://pasture-one-actor/object/cTKVUUsL3U0",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "edited_at": null,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "content": "no type \u26a0\ufe0f ",
  "filtered": [],
  "reblog": null,
  "account": {
    "id": "115157631664406598",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "discoverable": false,
    "indexable": false,
    "group": false,
    "created_at": "2025-09-06T00:00:00.000Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "uri": "http://pasture-one-actor/actor",
    "avatar": "http://mastodon/avatars/original/missing.png",
    "avatar_static": "http://mastodon/avatars/original/missing.png",
    "header": "http://mastodon/headers/original/missing.png",
    "header_static": "http://mastodon/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 16,
    "last_status_at": "2025-09-06",
    "hide_collections": true,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [],
  "mentions": [],
  "tags": [],
  "emojis": [],
  "quote": null,
  "card": null,
  "poll": null
}

Example 4

activity

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://mastodon/users/hippo"
  ],
  "id": "http://pasture-one-actor/activity/dc-ietgILk4",
  "published": "2025-09-06T13:40:27Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mastodon/users/hippo"
    ],
    "id": "http://pasture-one-actor/object/ymhAyQ2tKYQ",
    "published": "2025-09-06T13:40:27Z",
    "@context": "https://www.w3.org/ns/activitystreams",
    "content": "Hashtag not in @context \u26a0\ufe0f ",
    "tag": {
      "type": "Hashtag",
      "name": "#test"
    }
  }
}

mastodon

{
  "id": "115157632814434819",
  "created_at": "2025-09-06T13:40:27.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/ymhAyQ2tKYQ",
  "url": "http://pasture-one-actor/object/ymhAyQ2tKYQ",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "edited_at": null,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "content": "Hashtag not in @context \u26a0\ufe0f ",
  "filtered": [],
  "reblog": null,
  "account": {
    "id": "115157631664406598",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "discoverable": false,
    "indexable": false,
    "group": false,
    "created_at": "2025-09-06T00:00:00.000Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "uri": "http://pasture-one-actor/actor",
    "avatar": "http://mastodon/avatars/original/missing.png",
    "avatar_static": "http://mastodon/avatars/original/missing.png",
    "header": "http://mastodon/headers/original/missing.png",
    "header_static": "http://mastodon/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 17,
    "last_status_at": "2025-09-06",
    "hide_collections": true,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [],
  "mentions": [],
  "tags": [
    {
      "name": "test",
      "url": "http://mastodon/tags/test"
    }
  ],
  "emojis": [],
  "quote": null,
  "card": null,
  "poll": null
}

Example 5

activity

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Create",
  "actor": "http://pasture-one-actor/actor",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://mastodon/users/hippo"
  ],
  "id": "http://pasture-one-actor/activity/k4yTV_jqHD4",
  "published": "2025-09-06T13:40:28Z",
  "object": {
    "type": "Note",
    "attributedTo": "http://pasture-one-actor/actor",
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://mastodon/users/hippo"
    ],
    "id": "http://pasture-one-actor/object/0R96wD1h8Ls",
    "published": "2025-09-06T13:40:28Z",
    "@context": "https://www.w3.org/ns/activitystreams",
    "content": "Hashtag not in @context; as:Hashtag",
    "tag": {
      "type": "as:Hashtag",
      "name": "#test"
    }
  }
}

mastodon

{
  "id": "115157632878227588",
  "created_at": "2025-09-06T13:40:28.000Z",
  "in_reply_to_id": null,
  "in_reply_to_account_id": null,
  "sensitive": false,
  "spoiler_text": "",
  "visibility": "public",
  "language": null,
  "uri": "http://pasture-one-actor/object/0R96wD1h8Ls",
  "url": "http://pasture-one-actor/object/0R96wD1h8Ls",
  "replies_count": 0,
  "reblogs_count": 0,
  "favourites_count": 0,
  "edited_at": null,
  "favourited": false,
  "reblogged": false,
  "muted": false,
  "bookmarked": false,
  "content": "Hashtag not in @context; as:Hashtag",
  "filtered": [],
  "reblog": null,
  "account": {
    "id": "115157631664406598",
    "username": "actor",
    "acct": "actor@pasture-one-actor",
    "display_name": "Test Actor",
    "locked": false,
    "bot": false,
    "discoverable": false,
    "indexable": false,
    "group": false,
    "created_at": "2025-09-06T00:00:00.000Z",
    "note": "",
    "url": "http://pasture-one-actor/actor",
    "uri": "http://pasture-one-actor/actor",
    "avatar": "http://mastodon/avatars/original/missing.png",
    "avatar_static": "http://mastodon/avatars/original/missing.png",
    "header": "http://mastodon/headers/original/missing.png",
    "header_static": "http://mastodon/headers/original/missing.png",
    "followers_count": 0,
    "following_count": 0,
    "statuses_count": 18,
    "last_status_at": "2025-09-06",
    "hide_collections": true,
    "emojis": [],
    "fields": []
  },
  "media_attachments": [],
  "mentions": [],
  "tags": [],
  "emojis": [],
  "quote": null,
  "card": null,
  "poll": null
}