501 Not Implemented
The 501 HTTP response status code means the server does not have the capability to handle a particular feature needed to fulfill your request.
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Introduction
In Action
Sample
Conclusion
Introduction
When you encounter the 501 Not Implemented status code, it means the server does not have the capability to handle a particular feature needed to fulfill your request.
This could be due to an unsupported method or functionality on the server’s side. The response may be cached by default, but specific caching headers can be included in the response to modify this behavior if required.
In Action
When you encounter the 501 Not Implemented status code, it means the server lacks the capability to fulfill the request at that moment. It may be due to a missing or unfinished feature on the server’s side.
While the 405 Method Not Allowed code indicates a permanent lack of support for a specific functionality, 501 suggests that the feature might be available in the future.
The server may provide a Retry-After header to suggest a time when the client can try again. This status code is used when the server doesn’t recognize the HTTP request method and is unable to handle it at the moment, as stated in RFC 7231.
Sample
In the example, when the client requests a resource, the server responds with a 501 Not Implemented status code.
This means the server understands the request, but the specific feature or functionality required to fulfill the request is not currently supported. The server might add support for it in the future, but for now, it cannot handle the request.
Request
POST /requests?id=111&flag=start HTTP/1.1
Host: www.example.com
Response
HTTP/1.1 501 Not Implemented
Content-Type: text/html; charset=UTF-8
Content-Length: 202
< html>
< head>
< title>Function Not Implemented< /title>
< /head>
< body>
< p>Your request can not be completed because this functionality is currently under development.< /p>
< /body>
< /html>
Conclusion
The 501 Not Implemented HTTP status code indicates that the server cannot fulfill a specific request because it does not currently support the required feature or functionality. It suggests that the server might add support for it in the future, but for now, the requested action is not available.
