Common Error

400 BAD REQUEST

401 Unauthorized (authentication credential is missing or incorrect)

403 Forbidden (authenticated but lacks permissions)

404 Not Found

405 Method Not Allowed

409 Conflict

422 Unprocessable Entity

429 Too Many Requests (Backpressure)

444 No Response (unofficial)

500 Internal Server Error

502 Bad Gateway

503 Service Unavailable (Circuit Breaker)

504 Gateway Timeout

529 The Service Is Overloaded

530 Origin DNS Error (Cloudflare)

P.S. redirection

301 Moved Permanently

302 Found

304 Not Modified

307 Temporary Redirect

P.S. non-committal

202 Accepted

204 No Content (Preflight)