The Last-Modified response HTTP header contains a date and time when the origin server believes the resource was last modified. It is used as a validator to determine if the resource is the same as the previously stored one. 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.
| Header type | Representation header |
|---|---|
| Forbidden header name | no |
| CORS-safelisted response header | yes |
Last-Modified: <day-name>, <day> <month> <year> <hour>:<minute>:<second> GMT
One of "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", or "Sun" (case-sensitive).
2 digit day number, e.g. "04" or "23".
One of "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" (case sensitive).
4 digit year number, e.g. "1990" or "2016".
2 digit hour number, e.g. "09" or "23".
2 digit minute number, e.g. "04" or "59".
2 digit second number, e.g. "04" or "59".
GMTGreenwich Mean Time. HTTP dates are always expressed in GMT, never in local time.
Last-Modified: Wed, 21 Oct 2015 07:28:00 GMT
| Specification |
|---|
| HTTP Semantics # field.last-modified |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
Last-Modified |
Yes |
12 |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
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https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified