510 Not Extended
The server requires further extensions to the request before it will fulfil it. From an experimental extension framework that was never widely adopted.
At a glance
- Status code
- 510 Not Extended
- Class
- 5xx, server error, the request looked fine and the server failed
- Defined in
- RFC 2774, obsolete
- Cacheable by default
- no
- Response body
- Should describe the required extension.
In detail
RFC 2774 proposed a way to declare mandatory HTTP extensions per request. 510 was the server saying the declaration was missing.
The specification is obsolete and the code has no standard meaning today. Anything using it has invented its own.
Read the vendor documentation. There is no general rule to apply.
Examples
HTTP/1.1 510 Not Extended
Content-Type: text/plain
required extension declaration missingThings that catch people out
- Because it is obsolete, no client library has useful handling for it and it will surface as an unknown server error.
- Do not adopt it for a new API. A documented 400 or 428 communicates more.
Try it: HTTP Request Builder
Build a request with any method, headers and body, send it, and read the status line the server returns.
HTTP Request Builder
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curl -X GET 'https://api.example.com/endpoint' \
-H 'Content-Type: application/json'Showing a sample URL. Enter your endpoint above to update the snippet.
Related HTTP status codes
All http status codes →426 Upgrade Required
The server refuses to serve this request over the current protocol and names, in the Upgrade header, what it will accept.
428 Precondition Required
The server requires the request to be conditional, and refuses an unconditional one to prevent a lost update.
501 Not Implemented
The server does not support the functionality required to fulfil the request, typically an unrecognised request method.
511 Network Authentication Required
The client must authenticate to gain network access. This is the captive portal code, sent by the network rather than by the site you asked for.
100 Continue
The server has read the request headers, is willing to accept the body, and the client should now send it.
101 Switching Protocols
The server agrees to change protocol on this connection, which in practice almost always means upgrading to WebSocket.
Tools for this
- HTTP Request Builder Free online HTTP request builder - build and test HTTP requests with custom headers and body
- HTTP Headers Checker Free online HTTP headers checker - view HTTP response headers for any URL