510 Not Extended
5xx Server error
The request needs a further extension to be fulfilled.
| On the wire | HTTP/1.1 510 Not Extended |
|---|---|
| Code | 510 |
| Is it an error | Yes — this is an error |
| Category | 5xx Server error |
The problem is on the server side; retrying later is often worth it.
How to read this
- The first digit of a status code carries the meaning: 4 means the request, 5 means the server.
- 404 means "not there"; 403 means "there, but not for you". Swapping them makes debugging slower.
- Header names are case-insensitive — Content-Type and content-type are the same header.
- Caching and CORS problems usually come down to one header line, visible in the browser’s network tab.
Frequently asked questions
QWhat does HTTP 510 Not Extended mean?
The request needs a further extension to be fulfilled.
QWhat does 510 Not Extended look like on the wire?
It travels as HTTP/1.1 510 Not Extended
QIs 510 Not Extended an error?
Yes. A code starting with 4 blames the request; one starting with 5 blames the server.
QWhat group does 510 Not Extended belong to?
The 5xx server error group; the rest of that group is listed further down.