# 428 Precondition Required

> The origin server requires the request to be conditional.

Source: https://apiguide.dev/status-codes/428
Class: client-error
Defined in: RFC 6585 <https://www.rfc-editor.org/rfc/rfc6585.html>
Updated: 2026-07-09

## What does HTTP status code 428 mean?

The 428 Precondition Required status code indicates that the server requires the request to be conditional (using headers like If-Match or If-Modified-Since).

## When to use it in APIs

Used to prevent the "lost update" problem. The server refuses updates unless the client explicitly sends a version header constraint, forcing them to acknowledge the version state.

## How it compares to other codes

* **412 Precondition Failed**: Returned when the precondition check *fails*. 428 is returned when the precondition check was *omitted* entirely.