Cache-Control
Both directions
Sets how long and where the response may be cached — half of web performance lives here.
| On the wire | Cache-Control: … |
|---|---|
| Category | Both directions |
Headers that can appear on either side.
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 Cache-Control mean?
Sets how long and where the response may be cached — half of web performance lives here.
Q. What does Cache-Control look like on the wire?
It travels as Cache-Control: …
Q. Where does Cache-Control appear?
In both directions.
Q. What group does Cache-Control belong to?
The both directions group; the rest of that group is listed further down.