// http 5xx · server error
HTTP 501 Not Implemented
The server doesn't support the requested functionality.
What HTTP 501 Not Implemented means
501 Not Implemented means the server doesn't support the functionality needed to fulfil the request — for example, an HTTP method it doesn't recognise at all. It implies the capability may be added in future.
Which category is it?
501 is a 5xx code — Server error. 5xx means the server failed to fulfil an apparently valid request. It's the server's responsibility, not the caller's.
Common causes
- An HTTP method the server doesn't support
- A feature that isn't built yet
- A proxy that can't handle the request
How to fix it
- Use a supported method or feature
- Confirm the endpoint is fully implemented