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412Precondition Failed

A condition you attached to the request was not true, so the server refused to carry it out.

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Conditional requests use headers like If-Match to say "only do this if the resource is still the version I have". A 412 means it is not, so the operation was skipped rather than overwriting someone else's change.

This is how optimistic locking is implemented over HTTP, and a 412 is a success in the sense that it prevented data loss.

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Status codes

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1xx Informational (4)
2xx Success (10)
3xx Redirection (8)
4xx Client errors (31)
5xx Server errors (16)