# User OS

This wildcard will be substituted with the client's operating system (referring to the client connected to the browser).

The valid values for this wildcard include:

* mac
* win
* linux

{% hint style="info" %}
This wildcard tells you the operating system of your client, accessing the Helmut4 website, the operating system of your job/stream might be another - consider to have a look into this wildcard [local OS](https://docs.helmut.de/helmut4-releases/helmut4-components/streamdesigner/wildcards/local-environment-related-wildcards-6/local-os)
{% endhint %}

{% hint style="warning" %}
Please note that Helmut4 employs case sensitivity for all types of variables.
{% endhint %}