HTTP 501 Not Implemented
What a 501 Not Implemented response means, why it happens, and the fastest ways to fix it.
The server doesn't support the functionality required to fulfil the request — typically an HTTP method it doesn't recognize at all.
- Exotic/unsupported HTTP methods.
- Feature-flagged endpoints not enabled on this deployment.
- Verify the method and endpoint against the API version you're actually hitting.
Notes
HTTP status codes are defined in RFC 9110 (which replaced RFC 7231). The first digit is the class: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error.
Same class: 500 · 502 · 503 · 504 · 505 · 507
All codes: HTTP status code reference
Frequently asked questions
What does HTTP 501 mean?
HTTP 501 Not Implemented: The server doesn't support the functionality required to fulfil the request — typically an HTTP method it doesn't recognize at all.
How do I fix a 501 error?
Verify the method and endpoint against the API version you're actually hitting.
Is a 501 my fault or the server's?
501 is a server error — something on the server side (or between the proxy and the app) failed.