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HTTP Header
Last-Modified
CachingIndicates the date and time at which the origin server believes the resource was last modified.
HTTP header reference, syntax, examples, and developer usage.
What is the Last-Modified header?
The Last-Modified HTTP header is used to transmit metadata between a client and server as part of HTTP requests or responses.
HTTP headers define how content should be interpreted, cached, authenticated, secured, or processed by browsers and APIs.
Direction
This header may appear in both HTTP requests and responses.
Syntax
Last-Modified: <http-date>
Example
Last-Modified: Wed, 21 Oct 2015 07:28:00 GMT
Common use cases
- Browser cache validation
- Conditional requests
- Reducing repeated downloads
Common mistakes
- Using the header in the wrong request or response context
- Sending invalid header values
- Incorrect header syntax
- Assuming the header automatically changes server behaviour