> For the complete documentation index, see [llms.txt](https://docs.thousandeyes.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.thousandeyes.com/product-documentation/browser-synthetics/dual-chromium-option.md).

# Dual Chromium Option

The Dual Chromium option helps you validate browser synthetics tests against a newer Chromium track before that track becomes the default browser runtime. It applies to page load tests and transaction tests, which use [BrowserBot](https://docs.thousandeyes.com/product-documentation/global-vantage-points/enterprise-agents/what-is-browserbot) to run Chromium on ThousandEyes Cloud Agents and Enterprise Agents.

Chromium is an open-source project from Google, with upgrades issued outside the control of ThousandEyes. While you do not upgrade Chromium directly, the preparation described here helps you adapt to ThousandEyes Chromium updates as they occur.

{% hint style="info" %}
ThousandEyes does not upgrade to every new Chromium version. Instead, ThousandEyes selects Chromium versions on a rolling basis. The newer Chromium track might skip Chromium release numbers.

In test settings, **Default** is the current production Chromium track. **Newer when available** is the newer validation track.
{% endhint %}

Use Dual Chromium to test business-critical scripts, especially transaction tests with complex browser interactions, before the default Chromium track changes. This helps you identify script updates while production monitoring can remain on **Default**.

For Enterprise Agents, enable the **Dual Chromium Version** BrowserBot package on designated agents, then set selected page load or transaction tests to **Newer when available**. All Cloud Agents are enabled for Dual Chromium and can run the newer track without additional agent setup.

To configure agent and test settings, see [Configuring Dual Chromium](https://docs.thousandeyes.com/product-documentation/browser-synthetics/dual-chromium-option/configure-dual-chromium). To validate tests against the newer track, see [Working with Dual Chromium](https://docs.thousandeyes.com/product-documentation/browser-synthetics/dual-chromium-option/working-with-dual-chromium).