ErrorFindly
5015xx Server ErrorHigh

HTTP 501 Not Implemented

Defined in RFC 7231

What Does HTTP 501 Mean?

The server does not support the functionality required to fulfill the request. The server does not recognize the request method.

Common Causes

  1. 1HTTP method not implemented by the server
  2. 2Feature planned but not yet built
  3. 3Server doesn't support the request method (e.g., PATCH)
  4. 4Proxy doesn't understand the forwarded method

Impact

  • ⚠Requested operation is not available
  • ⚠Must use an alternative method or endpoint

Developer Fix

For web developers and application engineers

  1. 1Use a supported HTTP method instead
  2. 2Check server documentation for available methods
  3. 3Implement the missing functionality on the server

Server Admin Fix

For system administrators and DevOps engineers

  1. 1Implement support for the requested HTTP method
  2. 2Return proper Allow header listing supported methods
  3. 3Update server software if method should be supported

Frequently Asked Questions

What's the difference between 501 and 405?
405 means the server knows the method but it's not allowed for that specific resource. 501 means the server doesn't recognize or implement the method at all.
Is 501 the same as 'coming soon'?
Not exactly. 501 means the server doesn't support the functionality. While it can indicate a feature is not yet built, it's more commonly a permanent limitation of the server software.

Related HTTP Status Codes

405Method Not Allowed505HTTP Version Not Supported

About the Author

Web Infrastructure Team

Verified against official RFC specifications and real-world server configurations. HTTP status code behavior confirmed across Apache, Nginx, and Cloudflare.