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HTTP Status Code
428 Precondition Required
Client ErrorThe server requires the request to be conditional, usually to avoid conflicting updates.
HTTP status code reference, response example, common causes, fixes, and related status codes.
What does HTTP 428 Precondition Required mean?
HTTP 428 Precondition Required is a status code sent by a server to indicate the result of an HTTP request.
Status codes help browsers, APIs, apps, and backend systems understand whether a request succeeded, failed, was redirected, or needs additional action.
In practice, HTTP 428 Precondition Required usually appears when a server responds under specific request, validation, permission, or infrastructure conditions.
Response example
HTTP/1.1 428 Precondition Required
HTTP example
HTTP/1.1 428 Precondition Required
Relevant headers
If-Match
If-Match: "abc123"
Common causes
- Missing If-Match header
- Server requires conditional updates
How to fix it
- Send the required conditional headers
- Fetch the latest resource version before updating
Common mistakes
- Assuming the status code alone explains the full backend issue
- Ignoring related response headers that add important context
- Treating temporary errors as permanent failures
- Retrying too aggressively without checking the cause
- Debugging the frontend only when the problem is server-side
How browsers and APIs use it
Browsers, APIs, and backend services use HTTP status codes to understand the outcome of a request. Depending on the status code, an application may render content, retry a request, redirect the user, show an error, or trigger a different flow in the client or server.
Developer note
HTTP 428 is often used to force safe update behavior and prevent overwriting newer resource versions.