HTTP 417 Expectation Failed

The server cannot meet the requirements in the Expect request header.

Use 417 when an Expect extension or 100-continue expectation cannot be fulfilled.

httpstatus coderequest headers

Response (http)

HTTP/1.1 417 Expectation Failed

Use 417 when an Expect extension or 100-continue expectation cannot be fulfilled.

Common mistakes

Reading the full body before answering Expect: 100-continue; honor the expectation or answer 417 first.

Registry reference: RFC9110, Section 15.5.18

Sources