What it means

A 412 Precondition Failed response indicates the client included headers like If-Match or If-Unmodified-Since that the server could not satisfy. This is often used to prevent overwriting changes made by another user.

Common causes

• A conditional header like If-Match did not match the current resource state.
• The resource was modified by another request between reading and writing.

How to fix it

• Refresh the resource and retry with updated precondition headers.
• Handle the conflict in the application by reconciling the changes.