This is one of many protocol behaviors described in ActivityPub.

Identifier

urn:uuid:222934ff-e0e2-4b3b-a0d8-72908d1698b1

Content

clients... 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".

Origin

prefix To do this, clients MUST discover the URL of the actor's outbox from their profile

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".
 
suffix Servers MAY interpret a Content-Type or Accept header of application/activity+json as equivalent to application/ld+json; profile="https://www.w3.org/ns/activitystreams" for client-to-server interactions.

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

JSON

{
  "id": "urn:uuid:222934ff-e0e2-4b3b-a0d8-72908d1698b1",
  "type": "Behavior",
  "uuid": "222934ff-e0e2-4b3b-a0d8-72908d1698b1",
  "content": "clients... 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/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": "To do this, clients MUST discover the URL of the actor's outbox from their profile\n",
      "exact": "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",
      "suffix": "Servers MAY interpret a Content-Type or Accept header of application/activity+json as equivalent to application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\" for client-to-server interactions. \n"
    }
  },
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://socialweb.coop/ns/testing/context.json"
  ]
}