510 Not Extended HTTP Status Code


HTTP status code 510 stands for "Not Extended." It is used to indicate that further extensions to the request are required for the server to fulfill it. Essentially, this status code suggests that the server needs additional information from the client, which should be provided in the request's extensions, in order to process the request successfully.

This status code is part of the HTTP Extension Framework, described in RFC 2774, which introduces a mechanism for extending HTTP requests and responses. The framework was designed to allow new features to be introduced into HTTP without breaking existing clients and servers. When a server returns a 510 status code, it is typically accompanied by an optional "Warning" header in the response, indicating the required extensions that the client must support to proceed with the request.


510 Not Extended

Common Causes

The main cause of this error is when the server requires further extensions to fulfill the request, but these required extensions were not specified in the initial request from the client. In simpler terms, the server is indicating that additional extensions to the request are needed for it to be completed, but these were not provided by the client.

This situation could arise in scenarios where a server is configured to offer additional capabilities or require certain conditions to be met through the use of HTTP extensions. If a client's request does not include the necessary information on these extensions, the server may respond with a 510 status code to indicate that more information is needed.

The solution typically involves the client side, where the request needs to be modified to include the required extension parameters as specified by the server's requirements. This might include additional headers or other information that the server expects to process the request fully.

Browser Support

The following table will show you the current browser support for the 510 Not Extended HTTP status code.

Edge Chrome Firefox Opera Safari
Tablets / Mobile
Chrome Firefox Opera Safari Samsung Webview

Last updated by CSSPortal on: 1st April 2024