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Last-Modified

The Last-Modified response HTTP header contains the date and time at which the origin server believes the resource was last modified. It is used as a validator to determine if a resource received or stored is the same. Less accurate than an ETag header, it is a fallback mechanism. Conditional requests containing If-Modified-Since or If-Unmodified-Since headers make use of this field.

Syntax

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

Directives

<day-name>
One of "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", or "Sun" (case-sensitive).
<day>
2 digit day number, e.g. "04" or "23".
<month>
One of "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" (case sensitive).
<year>
4 digit year number, e.g. "1990" or "2016".
<hour>
2 digit hour number, e.g. "09" or "23".
<minute>
2 digit minute number, e.g. "04" or "59".
<second>
2 digit second number, e.g. "04" or "59".
GMT

Greenwich Mean Time. HTTP dates are always expressed in GMT, never in local time.

Examples

Last-Modified: Wed, 21 Oct 2015 07:28:00 GMT 

Specifications

Specification Title
RFC 7232, section 2.2: Last-Modified Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests

Browser compatibility

Feature Chrome Firefox Edge Internet Explorer Opera Safari
Basic Support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Edge mobile Firefox for Android IE mobile Opera Android iOS Safari
Basic Support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

See also

© 2005–2017 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified