---
title: cf.tls_client_extensions_sha1 · Cloudflare Ruleset Engine docs
description: The SHA-1 fingerprint of TLS client extensions, encoded in Base64 using big-endian format.
source_url:
  html: https://a74404c8.preview.developers.cloudflare.com/ruleset-engine/rules-language/fields/reference/cf.tls_client_extensions_sha1/index.md
  md: https://a74404c8.preview.developers.cloudflare.com/ruleset-engine/rules-language/fields/reference/cf.tls_client_extensions_sha1/
---

# cf.tls\_client\_extensions\_sha1

`cf.tls_client_extensions_sha1` String

The SHA-1 fingerprint of TLS client extensions, encoded in Base64 using big-endian format.

For the little-endian version of this field, refer to [`cf.tls_client_extensions_sha1_le`](https://developers.cloudflare.com/ruleset-engine/rules-language/fields/reference/cf.tls_client_extensions_sha1_le/).

Example value:

```txt
"OWFiM2I5ZDc0YWI0YWYzZmFkMGU0ZjhlYjhiYmVkMjgxNTU5YTU2Mg=="
```

Categories:

* Request
* SSL/TLS
