General REST API HTTP Status Codes

Reference: RFC 2616 - HTTP Status Code Definitions

400 BAD REQUEST: The request was invalid or cannot be otherwise served. An accompanying error message will explain further. For security reasons, requests without authentication are considered invalid and will yield this response.
401 UNAUTHORIZED: The authentication credentials are missing, or if supplied are not valid or not sufficient to access the resource.
403 FORBIDDEN: The request has been refused. See the accompanying message for the specific reason (most likely for exceeding rate limit).
404 NOT FOUND: The URI requested is invalid or the resource requested does not exists.
406 NOT ACCEPTABLE: The request specified an invalid format.
410 GONE: This resource is gone. Used to indicate that an API endpoint has been turned off.
429 TOO MANY REQUESTS: Returned when a request cannot be served due to the application’s rate limit having been exhausted for the resource.
500 INTERNAL SERVER ERROR: Something is horribly wrong.
502 BAD GATEWAY: The service is down or being upgraded. Try again later.
503 SERVICE UNAVAILABLE: The service is up, but overloaded with requests. Try again later.
504 GATEWAY TIMEOUT: Servers are up, but the request couldn’t be serviced due to some failure within our stack. Try again later.

200 OK: The request was successful and the response body contains the representation requested.
302 FOUND: A common redirect response; you can GET the representation at the URI in the Location response header.
304 NOT MODIFIED: There is no new data to return.

201 OK: The request was successful, we updated the resource and the response body contains the representation.
202 ACCEPTED: The request has been accepted for further processing, which will be completed sometime later.

202 ACCEPTED: The request has been accepted for further processing, which will be completed sometime later.
204 OK: The request was successful; the resource was deleted.

subfuzion/http-status-codes.md