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.

Support Table Preview

tag	Object	Activity
#test	Object	Activity
#test using as:Hashtag	Object	Activity
#test no type ⚠️	Object	Activity
#test Hashtag not in @context ⚠️	Object	Activity
#test Hashtag not in @context; as:Hashtag	Object	Activity

Objects

Object 1

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "attributedTo": "http://actor.example",
  "content": "text",
  "id": "http://actor.example/object/w5FVuM7PcUI",
  "published": "2025-09-09T09:32:39Z",
  "tag": {
    "name": "#test",
    "type": "Hashtag"
  },
  "to": [
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "type": "Note"
}

Object 2

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "attributedTo": "http://actor.example",
  "content": "using as:Hashtag",
  "id": "http://actor.example/object/WRl-piu9P5s",
  "published": "2025-09-09T09:32:39Z",
  "tag": {
    "name": "#test",
    "type": "as:Hashtag"
  },
  "to": [
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "type": "Note"
}

Object 3

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "attributedTo": "http://actor.example",
  "content": "no type \u26a0\ufe0f ",
  "id": "http://actor.example/object/Z49QfDu_6-o",
  "published": "2025-09-09T09:32:39Z",
  "tag": {
    "name": "#test"
  },
  "to": [
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "type": "Note"
}

Object 4

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "attributedTo": "http://actor.example",
  "content": "Hashtag not in @context \u26a0\ufe0f ",
  "id": "http://actor.example/object/0FkTK5MF1VM",
  "published": "2025-09-09T09:32:39Z",
  "tag": {
    "name": "#test",
    "type": "Hashtag"
  },
  "to": [
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "type": "Note"
}

Object 5

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "attributedTo": "http://actor.example",
  "content": "Hashtag not in @context; as:Hashtag",
  "id": "http://actor.example/object/DgAXob-yvqY",
  "published": "2025-09-09T09:32:39Z",
  "tag": {
    "name": "#test",
    "type": "as:Hashtag"
  },
  "to": [
    "https://www.w3.org/ns/activitystreams#Public"
  ],
  "type": "Note"
}

Activities

Activity 1

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "actor": "http://actor.example",
  "id": "http://actor.example/activity/HwnyCVxJScU",
  "object": {
    "attributedTo": "http://actor.example",
    "content": "text",
    "id": "http://actor.example/object/lAn6c1OqK8U",
    "published": "2025-09-09T09:32:39Z",
    "tag": {
      "name": "#test",
      "type": "Hashtag"
    },
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://remote.example/"
    ],
    "type": "Note"
  },
  "published": "2025-09-09T09:32:39Z",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://remote.example/"
  ],
  "type": "Create"
}

Activity 2

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "actor": "http://actor.example",
  "id": "http://actor.example/activity/bOt0Be1KGZE",
  "object": {
    "attributedTo": "http://actor.example",
    "content": "using as:Hashtag",
    "id": "http://actor.example/object/URrLhYbY288",
    "published": "2025-09-09T09:32:39Z",
    "tag": {
      "name": "#test",
      "type": "as:Hashtag"
    },
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://remote.example/"
    ],
    "type": "Note"
  },
  "published": "2025-09-09T09:32:39Z",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://remote.example/"
  ],
  "type": "Create"
}

Activity 3

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "Hashtag": "as:Hashtag",
      "sensitive": "as:sensitive"
    }
  ],
  "actor": "http://actor.example",
  "id": "http://actor.example/activity/f6SEdMQHdKw",
  "object": {
    "attributedTo": "http://actor.example",
    "content": "no type \u26a0\ufe0f ",
    "id": "http://actor.example/object/YDnG13zB1XI",
    "published": "2025-09-09T09:32:39Z",
    "tag": {
      "name": "#test"
    },
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://remote.example/"
    ],
    "type": "Note"
  },
  "published": "2025-09-09T09:32:39Z",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://remote.example/"
  ],
  "type": "Create"
}

Activity 4

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "actor": "http://actor.example",
  "id": "http://actor.example/activity/MFvAVT8cbrQ",
  "object": {
    "@context": "https://www.w3.org/ns/activitystreams",
    "attributedTo": "http://actor.example",
    "content": "Hashtag not in @context \u26a0\ufe0f ",
    "id": "http://actor.example/object/LiFvvhIUyxs",
    "published": "2025-09-09T09:32:39Z",
    "tag": {
      "name": "#test",
      "type": "Hashtag"
    },
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://remote.example/"
    ],
    "type": "Note"
  },
  "published": "2025-09-09T09:32:39Z",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://remote.example/"
  ],
  "type": "Create"
}

Activity 5

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "actor": "http://actor.example",
  "id": "http://actor.example/activity/E0RREzNRv4c",
  "object": {
    "@context": "https://www.w3.org/ns/activitystreams",
    "attributedTo": "http://actor.example",
    "content": "Hashtag not in @context; as:Hashtag",
    "id": "http://actor.example/object/2-ttb8HHRBU",
    "published": "2025-09-09T09:32:39Z",
    "tag": {
      "name": "#test",
      "type": "as:Hashtag"
    },
    "to": [
      "https://www.w3.org/ns/activitystreams#Public",
      "http://remote.example/"
    ],
    "type": "Note"
  },
  "published": "2025-09-09T09:32:39Z",
  "to": [
    "https://www.w3.org/ns/activitystreams#Public",
    "http://remote.example/"
  ],
  "type": "Create"
}