API Response Codes Cheatsheet

Understanding HTTP status codes is like having a secret decoder ring for the internet. These three-digit numbers are the server's way of telling your browser exactly how things are going—whether it's a "success," a "minor detour," or a "total meltdown."

Here is a breakdown of the most common status codes in the 200–500 range.

2xx: Success
200 OK: The standard "all clear." The request was successful.

201 Created: The request was successful and a new resource was created (common for POST requests).

204 No Content: The request was successful, but there’s no data to send back (e.g., deleting something).

3xx: Redirection
301 Moved Permanently: The URL of the requested resource has been changed permanently.

302 Found: The resource is temporarily at a different URL.

304 Not Modified: Tells the browser the cached version it has is still good; no need to re-download.

4xx: Client Errors
400 Bad Request: The server cannot understand the request due to invalid syntax.

401 Unauthorized: You need to provide valid credentials (log in) to see this.

403 Forbidden: The server understands the request but refuses to authorize it (even with a login).

404 Not Found: The classic. The server can't find the specific resource you asked for.

429 Too Many Requests: You've sent too many requests in a short amount of time (rate limiting).

5xx: Server Errors
500 Internal Server Error: A generic "catch-all" error message when the server hits an unexpected snag.

502 Bad Gateway: One server acting as a bridge got an invalid response from another server.

503 Service Unavailable: The server is currently down for maintenance or is overloaded.

504 Gateway Timeout: The server acting as a gateway timed out waiting for a response from the "upstream" server.