HTTP status codes are three-digit responses returned by a server when a client (like a browser or API call) makes a request. They are grouped into categories by their first digit.

1xx – Informational

These indicate the request is received and processing is continuing.

100 Continue – Request received, client should continue.
101 Switching Protocols – Server is switching protocols as requested.
102 Processing – Server has received the request and is processing, but no response yet.

2xx – Success

These mean the request was successfully received and processed.

200 OK – Request succeeded.
201 Created – Resource successfully created.
202 Accepted – Request accepted but not yet processed.
204 No Content – Request succeeded, but no content returned.
206 Partial Content – Partial response (e.g., when using ranges).

3xx – Redirection

These indicate the client must take additional steps.

301 Moved Permanently – Resource moved to a new permanent URL.
302 Found – Temporary redirect.
303 See Other – Redirect to another resource (commonly after POST).
304 Not Modified – Resource not changed, use cached version.
307 Temporary Redirect – Temporary redirect, same method.
308 Permanent Redirect – Permanent redirect, same method.

4xx – Client Errors

These indicate an error in the client’s request.

400 Bad Request – Malformed or invalid request.
401 Unauthorized – Authentication required or failed.
403 Forbidden – Client does not have permission.
404 Not Found – Resource not found.
405 Method Not Allowed – HTTP method not supported for this resource.
408 Request Timeout – Server timed out waiting for request.
409 Conflict – Request conflicts with resource state.
410 Gone – Resource is permanently removed.
429 Too Many Requests – Client sent too many requests (rate limiting).

5xx – Server Errors

These indicate the server failed to fulfill a valid request.

500 Internal Server Error – Generic server error.
501 Not Implemented – Server does not support the request method.
502 Bad Gateway – Server received an invalid response from upstream.
503 Service Unavailable – Server unavailable (overloaded or maintenance).
504 Gateway Timeout – Server didn’t receive a timely response.
505 HTTP Version Not Supported – Server doesn’t support the HTTP version used.

HTTP Status Codes