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Response

Last-Modified

Indicates the date and time the resource was last modified, used for cache validation.

Syntax

Last-Modified: <day-name>, <day> <month> <year> <hour>:<minute>:<second> GMT

Example

Last-Modified: Wed, 11 Mar 2026 08:00:00 GMT

Description

Last-Modified indicates when the resource was last changed. Browsers send it via If-Modified-Since for 304 responses.

Works well for static files but has second-level precision limitations.

For more precise validation, use ETag in addition to Last-Modified.

How real sites send this header

Home-page responses of 503 popular sites from the enterno.io /check catalogue, checked in the last 30 days.

26.0% (131 of 503) send Last-Modified.

See it on: discord.com, beget.com, angular.dev, bitbucket.org, datadog.com

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Related Headers

Connection
Controls whether the network connection stays open after the current transaction finishes.
Content-Disposition
Indicates whether the response should be displayed inline or downloaded as a file attachment.
Content-Encoding
Specifies the compression algorithm applied to the response body, such as gzip or brotli.
Content-Length
Specifies the size of the response body in bytes.
Content-Type
Indicates the media type of the response body, telling the browser how to interpret and display the content.
Date
Indicates the date and time at which the response was generated by the server.

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