---
name: "If-None-Match"
area: "API"
kind: "HTTP header"
parent: "up.protocol module"
url: "https://unpoly.com/api/If-None-Match"
---
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# If-None-Match

This request header contains the ETag of a fragment that is being reloaded.

The server can use the header value to prevent unnecessary re-rendering of unchanged content. See [Conditional requests](https://unpoly.com/learn/conditional-requests.md) for details and examples.

The header is only set when Unpoly knows the ETag of the loading fragment. For this the fragment must have been rendered with an [`ETag`](https://unpoly.com/api/ETag.md) response header or [`[up-etag]`](https://unpoly.com/api/up-etag.md) attribute.

## Format {#format}

The `If-None-Match` header uses the same format as the [`ETag`](https://unpoly.com/api/ETag.md) header:

```http
If-None-Match: W/"55e4d42a148795d9f25f89d4"
```