HTTP 428 Precondition Required

What HTTP 428 means

To prevent lost updates, an API can insist that every PUT or PATCH includes If-Match with the ETag the client last saw. Requests without it get 428. Requests whose ETag no longer matches get 412.

Retrying

No. Fix the request first; sending it again unchanged will get the same response.

Example response

HTTP/1.1 428 Precondition Required
Date: Wed, 21 Oct 2026 10:30:00 GMT
Content-Type: application/json

How to return 428

res.status(428).json({ error: 'Precondition Required' });

from fastapi import HTTPException

raise HTTPException(status_code=428, detail="Precondition Required")

http.Error(w, http.StatusText(http.StatusPreconditionRequired), http.StatusPreconditionRequired)

location /private/ {
    return 428;
}

Related status codes

• 412 Precondition Failed : A condition in the request headers, such as If-Match, was not met.
• 409 Conflict : The request conflicts with the current state of the resource.

Other 4xx status codes

400 Bad Request · 401 Unauthorized · 402 Payment Required · 403 Forbidden · 404 Not Found · 405 Method Not Allowed · 406 Not Acceptable · 407 Proxy Authentication Required · 408 Request Timeout · 409 Conflict · 410 Gone · 411 Length Required · 412 Precondition Failed · 413 Content Too Large · 414 URI Too Long · 415 Unsupported Media Type · 416 Range Not Satisfiable · 417 Expectation Failed · 418 I’m a Teapot · 421 Misdirected Request · 422 Unprocessable Content · 423 Locked · 424 Failed Dependency · 425 Too Early · 426 Upgrade Required · 429 Too Many Requests · 431 Request Header Fields Too Large · 444 No Response · 451 Unavailable For Legal Reasons · 499 Client Closed Request

See the full list of HTTP status codes.

Sources

• RFC 6585
• IANA HTTP Status Code Registry
• MDN: 428 Precondition Required

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Frequently asked questions