4xx Client error

417 Expectation Failed

The server can't meet the Expect header's requirement.

What 417 means

Almost always about Expect: 100-continue, which some servers and proxies don't support.

Common causes

A client sent Expect: 100-continue to a server that rejects it.

How to fix it

If you're calling an API

Remove the Expect header (curl: -H 'Expect:').

If you run the server

Support or ignore Expect: 100-continue.

Should you retry?

Without the Expect header.

Example response

HTTP

HTTP/1.1 417 Expectation Failed
Content-Type: application/problem+json

{
  "type": "about:blank",
  "title": "Expectation Failed",
  "status": 417,
  "detail": "The server can't meet the Expect header's requirement."
}

Related headers: Expect.

Defined in: RFC 9110 (HTTP Semantics). 417 is a client error: change the request before retrying.

Debugging an API call? Convert your request with the cURL converter, check the response with the JSON formatter, or see whether the API is down on its status page.

HTTP 417 FAQ

What does HTTP 417 mean?

417 Expectation Failed: The server can't meet the Expect header's requirement. Almost always about Expect: 100-continue, which some servers and proxies don't support.

Is 417 a client or server error?

It's a client error (4xx): something about the request needs to change before it can succeed.

How do I fix a 417 error?

Remove the Expect header (curl: -H 'Expect:').

Should I retry after a 417?

Without the Expect header.

Other 4xx status codes

All HTTP status codes