---
title: "417 Expectation Failed — what it means and how to fix it"
description: "The server cannot meet the requirement set in the request's Expect header. What causes an HTTP 417, what to try as a visitor, and what to check if it is your own site."
url: https://atoneplace.net/error/417/
site: "At One Place"
---

# HTTP 417 — Expectation Failed

**HTTP 417: Expectation Failed**

The server cannot meet the requirement set in the request's Expect header.

## What 417 actually means

The only `Expect` value ever defined is `100-continue`, so in practice this means a server or proxy in the path will not play the "send me your headers first" game. It typically appears when a client that adds `Expect: 100-continue` automatically — curl does this for bodies over 1 KB — talks to an older proxy or a server that does not implement it. The fix is to stop sending the expectation.

## Common causes

- A proxy or server that does not support `Expect: 100-continue`
- curl adding the header automatically for a large body
- A legacy HTTP/1.0 intermediary in the request path

## If you're just trying to view the page

1. Nothing in a browser — browsers do not send `Expect` headers
2. If a desktop tool produced it, check for an update; older HTTP libraries hit this more often

## If it's your site

1. Disable the expectation: with curl, add `-H "Expect:"` to send an empty header and suppress it
2. In .NET, set `ServicePointManager.Expect100Continue = false`
3. On the server, accept and honour `100-continue` rather than rejecting it — it is cheap to support

## Reference

- **Status code:** 417
- **Reason phrase:** Expectation Failed
- **Category:** 4xx — Client Error
- **Defined in:** RFC 9110 §15.5.18

## Common questions

### What does HTTP 417 mean?

The server cannot meet the requirement set in the request's Expect header. The only `Expect` value ever defined is `100-continue`, so in practice this means a server or proxy in the path will not play the "send me your headers first" game. It typically appears when a client that adds `Expect: 100-continue` automatically — curl does this for bodies over 1 KB — talks to an older proxy or a server that does not implement it.

### How do I fix a 417 error?

Nothing in a browser — browsers do not send `Expect` headers

### Is 417 a client error or a server error?

417 is in the 4xx range, which means client error. The request itself was the problem, so retrying it unchanged will usually return the same code.

## Related pages

- [404 Not Found](https://atoneplace.net/error/404/)
- [403 Forbidden](https://atoneplace.net/error/403/)
- [401 Unauthorized](https://atoneplace.net/error/401/)
- [429 Too Many Requests](https://atoneplace.net/error/429/)
- [400 Bad Request](https://atoneplace.net/error/400/)
- [413 Content Too Large](https://atoneplace.net/error/413/)
- [422 Unprocessable Content](https://atoneplace.net/error/422/)
- [405 Method Not Allowed](https://atoneplace.net/error/405/)
- [409 Conflict](https://atoneplace.net/error/409/)
- [415 Unsupported Media Type](https://atoneplace.net/error/415/)
- [408 Request Timeout](https://atoneplace.net/error/408/)
- [410 Gone](https://atoneplace.net/error/410/)

## Sources

- Hypertext Transfer Protocol (HTTP) Status Code Registry — IANA (https://www.iana.org/assignments/http-status-codes/)
- RFC 9110: HTTP Semantics — IETF (https://www.rfc-editor.org/rfc/rfc9110.html)