Server error · HTTP reference

501Not Implemented

The server does not implement the requested functionality.

The company behind the code.

For development teams building missing features.

501Not Implemented

The server does not implement the requested functionality.

Available

For development teams building missing features.

Your logo, your message, your corner of the internet.

Try the response.

Returns this HTTP status with the current sponsor’s name, advertising message and website. Useful for testing how your app handles a response.

GET /responses/501Open response RFC 9110, section 15.6.2

This is an independent project. Sponsorship does not confer ownership of HTTP standards.

Understanding 5xx responses.

Server error responses describe failures in the server or its upstream services.

Inspect server and gateway logs, and check service availability. Retrying requests that change data can duplicate an operation unless the API supports safe retries.

Reference reviewed 5 September 2026. How we use sources.

Related status codes.

Browse all 60 codes