lightmy.dayINSTANT ANSWERS

Client error

HTTP 412: Precondition Failed

HTTP 412 means a request precondition failed.

Meaning

The server rejected the request because a conditional header did not match.

Common causes

If-Match, If-Unmodified-Since, or similar precondition headers can fail.

What to check

Refresh the resource state and resend the request with the correct conditional header.

Example response

HTTP/1.1 412 Precondition Failed

References

Registry: IANA HTTP Status Code Registry
Spec: RFC 9110 §15.5.13
Guide: MDN 412 Precondition Failed

Related HTTP status codes

Nearby codes often answer the next debugging question.

400 Bad RequestHTTP 400 means the server could not understand the request.409 ConflictHTTP 409 means the request conflicts with the current resource state.422 Unprocessable ContentHTTP 422 means the request syntax is valid but the content cannot be processed.