428 Precondition Required
4xx Client error
The request must carry a condition — this is how lost updates are prevented.
| On the wire | HTTP/1.1 428 Precondition Required |
|---|---|
| Code | 428 |
| 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 428 Precondition Required mean?
The request must carry a condition — this is how lost updates are prevented.
Q. What does 428 Precondition Required look like on the wire?
It travels as HTTP/1.1 428 Precondition Required
Q. Is 428 Precondition Required an error?
Yes. A code starting with 4 blames the request; one starting with 5 blames the server.
Q. What group does 428 Precondition Required belong to?
The 4xx client error group; the rest of that group is listed further down.