5xx Server ErrorHTTP Status Code Reference

HTTP 501 Not Implemented— What It Means, Causes & How to Fix It

The server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and cannot support it for any resource.

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Common Causes

  • Server doesn't support the HTTP method used
  • Feature not yet implemented on the server
  • Using a method the server intentionally doesn't support

How to Fix

  1. 1Use a different HTTP method that the server supports
  2. 2Check if the feature will be available in a future update
  3. 3Implement the missing functionality on the server

Example

HTTP 501 Not Implemented
PATCH /api/resource HTTP/1.1

→ 501 Not Implemented
→ "PATCH method is not supported"

Related Server Error Codes

500

Internal Server Error

502

Bad Gateway

503

Service Unavailable

504

Gateway Timeout

505

HTTP Version Not Supported

506

Variant Also Negotiates

507

Insufficient Storage

508

Loop Detected

510

Not Extended

511

Network Authentication Required

Commonly Referenced Status Codes

The most frequently searched HTTP status codes

200OK201Created204No Content301Moved Permanently302Found400Bad Request401Unauthorized403Forbidden404Not Found422Unprocessable Content429Too Many Requests500Internal Server Error502Bad Gateway503Service Unavailable504Gateway Timeout

Related Tools

HTTP Status LookupAPI Request BuildercURL GeneratorHTTP Header ViewerHTTP Header DiffRedirect Checker