HTTP 409 — Conflict
The request could not be processed because of conflict in the request
When to use it
Use status 409 when this is the correct HTTP response semantic: The request could not be processed because of conflict in the request
Request and response example
POST /users HTTP/1.1
Host: api.example.com
Content-Type: application/json
{"email":"ada@example.com"}
HTTP/1.1 409 Conflict
Content-Type: application/json
{"error":"Email already exists"}