---
title: cf.tls_client_auth.cert_issuer_ski · Cloudflare Ruleset Engine docs
description: The Subject Key Identifier (SKI) of the direct issuer of the certificate in the request.
source_url:
  html: https://a74404c8.preview.developers.cloudflare.com/ruleset-engine/rules-language/fields/reference/cf.tls_client_auth.cert_issuer_ski/index.md
  md: https://a74404c8.preview.developers.cloudflare.com/ruleset-engine/rules-language/fields/reference/cf.tls_client_auth.cert_issuer_ski/
---

# cf.tls\_client\_auth.cert\_issuer\_ski

`cf.tls_client_auth.cert_issuer_ski` String

The Subject Key Identifier (SKI) of the direct issuer of the certificate in the request.

This field is only filled in if the request includes a client certificate for [mTLS authentication](https://developers.cloudflare.com/ssl/client-certificates/enable-mtls/).

Example value:

```txt
"8204924CF49D471E855862706D889F58F6B784D3"
```

Categories:

* Request
* mTLS
