Error 417

417 Expectation Failed

The 417 Expectation Failed status code indicates that the server could not meet the requirements specified in the Expect header of the client's request.

For more details, refer to RFC 7231 ↗.

Common use cases

Some clients use the Expect header, such as Expect: 100-continue, to verify if the server is ready to receive a large payload, and if the server cannot fulfill this expectation, it returns a 417 response. Similarly, a server may reject a request with this error if the client includes an Expect header with unsupported or invalid values.

Cloudflare-specific information

Cloudflare typically forwards this response from the origin server if it encounters an issue related to unsupported or unfulfilled Expect headers in the client's request.