This is one of many protocol behaviors described in ActivityPub.

Identifier

urn:uuid:48aca38c-b8bf-4e57-8bb8-0065058aada1

Content

clients MUST discover the URL of the actor's outbox from their profile

Origin

prefix Client to server interaction takes place through clients posting Activities to an actor's outbox. To do this,

clients MUST discover the URL of the actor's outbox from their profile
 
suffix and then MUST make an HTTP POST request to this URL with the Content-Type of application/ld+json; profile="https://www.w3.org/ns/activitystreams".

https://www.w3.org/TR/activitypub/

JSON

{
  "id": "urn:uuid:48aca38c-b8bf-4e57-8bb8-0065058aada1",
  "type": "Behavior",
  "uuid": "48aca38c-b8bf-4e57-8bb8-0065058aada1",
  "content": "clients MUST discover the URL of the actor's outbox from their profile\n",
  "context": [
    "https://www.w3.org/TR/activitypub/",
    {
      "name": "Client to server interaction"
    },
    {
      "name": "clients posting Activities to an actor's outbox"
    }
  ],
  "origin": {
    "source": "https://www.w3.org/TR/activitypub/",
    "section": {
      "id": "https://www.w3.org/TR/activitypub/#x6-client-to-server-interactions",
      "branch": [
        6
      ]
    },
    "selector": {
      "type": "TextQuoteSelector",
      "prefix": "Client to server interaction takes place through clients posting Activities to an actor's outbox. To do this, \n",
      "exact": "clients MUST discover the URL of the actor's outbox from their profile\n",
      "suffix": "and then MUST make an HTTP POST request to this URL with the Content-Type of application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\".\n"
    }
  },
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://socialweb.coop/ns/testing/context.json"
  ]
}