HTTP Last-Modified Header
Indicates the date and time when the resource was last modified. Used for cache validation with If-Modified-Since.
Purpose
Tells clients when the resource was last changed, enabling conditional requests to check for updates efficiently.
Last-Modified: <day-name>, <day> <month> <year> <hour>:<min>:<sec> GMT Example: Last-Modified: Mon, 18 May 2026 12:00:00 GMT
Code Examples
See how to use the Last-Modified header in different tools and languages.
Related Headers
If-Modified-Since
Makes the request conditional. The server responds with 304 Not Modified if the resource has not been modified since the specified date.
ETag
An identifier for a specific version of a resource. Used for cache validation and conditional requests to avoid re-downloading unchanged content.
Cache-Control
Specifies caching directives for both requests and responses. Controls how and for how long content is cached by browsers and intermediate caches.
Date
Contains the date and time when the message was originated. Every HTTP response should include this header.