---
title: "409 Conflict — what it means and how to fix it"
description: "The request cannot be completed because it clashes with the current state of the resource. What causes an HTTP 409, what to try as a visitor, and what to check if it is your own site."
url: https://atoneplace.net/error/409/
site: "At One Place"
---

# HTTP 409 — Conflict

**HTTP 409: Conflict**

The request cannot be completed because it clashes with the current state of the resource.

## What 409 actually means

The request is well formed and you are allowed to make it, but doing so right now would break something. The two classic cases are a duplicate — registering an email address that already exists — and a lost update, where two people edited the same record and the second write would silently discard the first. A 409 is a request that could succeed later or in a different order, which distinguishes it from 400 and 422.

## Common causes

- A unique constraint violated: username, email or slug already taken
- Optimistic concurrency failure — the `If-Match` ETag no longer matches
- Two edits to the same resource landing at once
- Trying to delete something other records still depend on
- A version control style conflict in a sync API

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

1. Reload the page to get the current version, then reapply your change
2. If it is a signup or rename, choose a different value — something already uses the one you picked
3. Check whether someone else edited the same item while you had it open

## If it's your site

1. Say what conflicted in the response body; "Conflict" alone forces the client to guess
2. Use ETags with `If-Match` so conflicts are detected rather than silently overwriting
3. Distinguish "already exists" from "version mismatch" with a machine-readable error code
4. Where safe, make the operation idempotent so a retry succeeds instead of conflicting

## Reference

- **Status code:** 409
- **Reason phrase:** Conflict
- **Category:** 4xx — Client Error
- **Defined in:** RFC 9110 §15.5.10

## Common questions

### What does HTTP 409 mean?

The request cannot be completed because it clashes with the current state of the resource. The request is well formed and you are allowed to make it, but doing so right now would break something. The two classic cases are a duplicate — registering an email address that already exists — and a lost update, where two people edited the same record and the second write would silently discard the first.

### How do I fix a 409 error?

Reload the page to get the current version, then reapply your change

### Is 409 a client error or a server error?

409 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/)
- [415 Unsupported Media Type](https://atoneplace.net/error/415/)
- [408 Request Timeout](https://atoneplace.net/error/408/)
- [410 Gone](https://atoneplace.net/error/410/)
- [451 Unavailable For Legal Reasons](https://atoneplace.net/error/451/)

## 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)