If-Match required

HTTP 428 · precondition-required — ← all Webpath errors

This write must carry an If-Match precondition and none was sent.

How to recover. Read the file first, then retry with If-Match set to its ETag.

Example response

{
  "type": "https://muse.as/a/webpath/errors/precondition-required",
  "title": "If-Match required",
  "status": 428,
  "detail": "Read the file first, then retry with If-Match set to its ETag."
}

This page documents the precondition-required error type returned in Webpath RFC 7807 application/problem+json responses. The machine-readable detail field carries a recovery hint you can show a user verbatim — see the Spec §12 and API Reference.