4xx Client Errors
HTTP 417 Expectation Failed
The Expect header in the request cannot be met by the server.
When is 417 used?
- 100-continue expectation cannot be met
How to handle a 417 response
Inspect the request — URL, method, headers, credentials, and body. Retrying the same request unchanged will usually fail again; 429 is the exception, where you should wait for the Retry-After period.
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 417 from your server
Node.js (Express)
res.status(417).json({ message: 'Expectation Failed' });Python (Flask)
return {"message": "Expectation Failed"}, 417Go (net/http)
w.WriteHeader(417)Frequently Asked Questions
What does HTTP 417 mean?
417 Expectation Failed: The Expect header in the request cannot be met by the server.
Is 417 an error?
Yes. 417 is in the 4xx Client Errors class. Client errors: the request is malformed, unauthorized, or targets something that does not exist.