HTTP 510 Not Extended

5xx Server Error

5xx Server Error RFC 2774, Section 7

What is HTTP 510 Not Extended?

The 510 (Not Extended) status code indicates that the policy for accessing the resource has not been met in the request. This is related to the HTTP Extension Framework, which allows for additional extensions to be negotiated between client and server.

Common Use Cases

HTTP extension policy negotiation
Custom protocol extension requirements

Usage Example

The HTTP Extension Framework (RFC 2774) defines 510 for when mandatory extensions are missing. In practice, this status is rarely implemented. If you need to require specific extensions, consider using custom headers or API versioning strategies instead.

// Practical alternative - requiring a custom header
if (! $request->header('X-API-Version')) {
    return response()->json([
        'error' => 'API version header required',
    ], 510);
}