HTTP 412 Precondition Failed

One or more request conditions evaluated to false.

Use 412 when If-Match, If-Unmodified-Since, or another conditional request fails.

httpstatus codeconditionalconcurrency

Response (http)

HTTP/1.1 412 Precondition Failed

Use 412 when If-Match, If-Unmodified-Since, or another conditional request fails.

Common mistakes

Evaluating If-Match with a weak validator, or comparing against a different representation than the request targeted.

Registry reference: RFC9110, Section 15.5.13

Sources