Last-Modified
Response headers
When the resource last changed; conditional requests compare against it.
| On the wire | Last-Modified: … |
|---|---|
| Category | Response headers |
Headers the server attaches when it answers.
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
QWhat does HTTP Last-Modified mean?
When the resource last changed; conditional requests compare against it.
QWhat does Last-Modified look like on the wire?
It travels as Last-Modified: …
QWhere does Last-Modified appear?
In response headers.
QWhat group does Last-Modified belong to?
The response headers group; the rest of that group is listed further down.