412 Precondition Failed

Your 'only if' didn't hold up.

What it properly means

The client set preconditions in its headers that the server does not meet.

Class
4xx Client error: you fucked up
Defined in
RFC 9110, section 15.5.13

Get one yourself

This endpoint really answers with 412. Point your client at it and see what it does.

curl -i https://httpcodes.dev/api/412

People mix this up with

  • 409 Conflict412

    Which kind of clash?

    409 means the request conflicts with the current state, such as creating something that already exists. 412 means the client sent a condition like If-Match and it turned out to be false.