501

What 501 means

The server does not recognise the request method or lacks the capability to handle it. Unlike 405, which means "this method is not allowed here", 501 means the server does not support the method anywhere at all.

Common causes

• •An HTTP method the server does not implement, such as PATCH on older configurations.
• •A proxy that does not support the requested feature.
• •A placeholder route left in place for an unbuilt endpoint.

How to fix it

Confirm the method is supported by every hop, not just your application — a reverse proxy can reject a method your application handles perfectly well.

When 501 is the right answer

There are legitimate uses for 501. An API that publishes a route before implementing it can return 501 rather than 404, which tells a caller the endpoint is real but not ready — a meaningfully different message. Some frameworks also return 501 for methods like PATCH or PROPFIND that the server was never built to handle.\n\nThe trap is that 501 can come from anywhere in the chain. A reverse proxy, WAF, or CDN may reject a method before your application ever sees the request, so the code you are reading was not necessarily generated by your code. Test against the origin directly to establish which hop is refusing.

Often confused with

← All HTTP status codes