# 417 Expectation Failed

> The server cannot meet the requirements of the Expect request header.

Source: https://apiguide.dev/status-codes/417
Class: client-error
Defined in: RFC 9110, Section 15.5.18 <https://www.rfc-editor.org/rfc/rfc9110.html#section-15.5.18>
Updated: 2026-07-09

## What does HTTP status code 417 mean?

The 417 Expectation Failed status code indicates that the server is unable to satisfy the expectations set in the client's `Expect` request header.

## When to use it in APIs

Occasionally returned if a client sends `Expect: 100-continue` but the server cannot comply.

## How it compares to other codes

* **100 Continue**: The positive response indicating that the expectation *can* be met.