Glossary: System Design Basics in JavaScript

Status code

Also written: HTTP status code, 200, 201, 400, 401, 403, 404, 409, 429, 500, 503

The number that starts an HTTP response: 2xx means success, 4xx the client's mistake, 5xx the server's problem. Common codes include 200 OK, 201 Created, 301 moved for good, 302 moved for now, 400 Bad Request, 401 Unauthorized (missing or wrong token), 403 Forbidden (known but not allowed), 404 Not Found, 409 Conflict, 429 Too Many Requests, 500 Internal Server Error and 503 Service Unavailable.