---
title: "428 Precondition Required — what it means and how to fix it"
description: "The server insists the request be conditional, to stop it from silently overwriting someone else's changes. What causes an HTTP 428, what to try as a visitor, and what to check if it is your own site."
url: https://atoneplace.net/error/428/
site: "At One Place"
---

# HTTP 428 — Precondition Required

**HTTP 428: Precondition Required**

The server insists the request be conditional, to stop it from silently overwriting someone else's changes.

## What 428 actually means

A server that cares about lost updates can require every write to carry an `If-Match` header, so that it can reject the write if the resource changed since the client last read it. A 428 is the server refusing an unconditional write and telling the client to fetch the current ETag and try again. It is the preventive counterpart to 412: 428 stops the dangerous request being made, 412 reports that the safe one lost the race.

## Common causes

- A PUT or PATCH sent without an `If-Match` header to an API that requires one
- A client that fetched a resource but discarded the ETag
- An API enforcing optimistic concurrency on all writes

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

1. Nothing directly — this is a contract between the client software and the API
2. Reloading and retrying usually resolves it, since the client re-reads the current version

## If it's your site

1. GET the resource, keep its ETag, and send it back as `If-Match` on the write
2. Serve stable ETags on every resource you require preconditions for
3. Say which header is missing in the response body; "Precondition Required" alone does not name it

## Reference

- **Status code:** 428
- **Reason phrase:** Precondition Required
- **Category:** 4xx — Client Error
- **Defined in:** RFC 6585 §3

## Common questions

### What does HTTP 428 mean?

The server insists the request be conditional, to stop it from silently overwriting someone else's changes. A server that cares about lost updates can require every write to carry an `If-Match` header, so that it can reject the write if the resource changed since the client last read it. A 428 is the server refusing an unconditional write and telling the client to fetch the current ETag and try again.

### How do I fix a 428 error?

Nothing directly — this is a contract between the client software and the API

### Is 428 a client error or a server error?

428 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)