428 Precondition Required
4xx Client Error
RFC 6585
You need to send a precondition header — we won't update blindly.
What 428 Precondition Required means {#what}
The server requires conditional request headers (like If-Match) to prevent the “lost update” problem, but the client didn’t send them. The server is enforcing safe concurrency practices.
When you’ll see a 428 {#when}
- APIs that enforce optimistic concurrency and require ETags on updates
- Server-side policy requiring
If-Matchbefore any PUT
When to use 428 {#use}
- Use to enforce safe updates on resources that could be modified concurrently