510 Not Extended
5xx Server Error
RFC 2774
The server needs an HTTP extension you didn't include.
What 510 Not Extended means {#what}
The server requires an HTTP extension (defined in the request policy) to process the request, but the client’s request doesn’t declare it. Extremely niche.
When you’ll see a 510 {#when}
- Servers requiring mandatory HTTP extensions (RFC 2774)
- Essentially never in practice — the extension framework was never widely adopted