412 Precondition Failed
4xx Client error
A condition attached to the request did not hold.
| On the wire | HTTP/1.1 412 Precondition Failed |
|---|---|
| Code | 412 |
| Is it an error | Yes — this is an error |
| Category | 4xx Client error |
The problem is on the request side; sending the same thing again will fail again.
How to read this
- The first digit of a status code carries the meaning: 4 means the request, 5 means the server.
- 404 means "not there"; 403 means "there, but not for you". Swapping them makes debugging slower.
- Header names are case-insensitive — Content-Type and content-type are the same header.
- Caching and CORS problems usually come down to one header line, visible in the browser’s network tab.
Frequently asked questions
Q. What does HTTP 412 Precondition Failed mean?
A condition attached to the request did not hold.
Q. What does 412 Precondition Failed look like on the wire?
It travels as HTTP/1.1 412 Precondition Failed
Q. Is 412 Precondition Failed an error?
Yes. A code starting with 4 blames the request; one starting with 5 blames the server.
Q. What group does 412 Precondition Failed belong to?
The 4xx client error group; the rest of that group is listed further down.