---
name: "Last-Modified"
area: "API"
kind: "HTTP header"
parent: "up.protocol module"
url: "https://unpoly.com/api/Last-Modified"
---
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# Last-Modified

This response header contains the time when the content in the response body was last modified.

Last modification times can be used to prevent unnecessary re-rendering of unchanged content. See [Conditional requests](https://unpoly.com/learn/conditional-requests.md) for details and examples.

## Format {#format}

The header value is a date/time in [RFC 1123](https://www.rfc-editor.org/rfc/rfc1123) format:

```http
Last-Modified: Wed, 15 Nov 2000 13:11:22 GMT
```

For a readable description of the time format, see [MDN](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified).

## Alternatives {#alternatives}

Instead of sending this header, the server may also render fragments with [`[up-time]`](https://unpoly.com/api/up-time.md) attributes.