5xx Server Errors
HTTP 510 Not Extended
The server requires further extensions to the request for it to be fulfilled.
When is 510 used?
- Mandatory extension not implemented by client
How to handle a 510 response
The problem is on the server side. Check server and proxy logs, retry idempotent requests with exponential backoff, and alert on sustained 5xx rates.
Check the status code a URL returns from the command line:
curl -s -o /dev/null -w "%{http_code}\n" https://example.comHow to return 510 from your server
Node.js (Express)
res.status(510).json({ message: 'Not Extended' });Python (Flask)
return {"message": "Not Extended"}, 510Go (net/http)
w.WriteHeader(510)Frequently Asked Questions
What does HTTP 510 mean?
510 Not Extended: The server requires further extensions to the request for it to be fulfilled.
Is 510 an error?
Yes. 510 is in the 5xx Server Errors class. Server errors: the server failed to fulfil an apparently valid request.