201
2xx SuccessCreated
The request succeeded and a new resource was created as a result.
201 Created confirms that a request succeeded and led to a new resource. It's the correct response to a POST or PUT that creates something. A well-behaved API includes a Location header pointing at the new resource's URL, and often returns the created object in the body.
What 201 looks like on the wire
POST /api/articles HTTP/1.1
Host: api.example.com
Content-Type: application/json
{"title": "Hello world"}
HTTP/1.1 201 Created
Location: /api/articles/1207About 2xx Success
The request was received, understood, and accepted. This is what you want to see.
Where it's defined
201 Created is defined in RFC 9110 §15.3.2. MDN's 201 reference covers browser behavior and examples.