# Extension for Silverlight

> The first step is to uninstall any previous Silverlight Runtime you may have and install **Silverlight Developer Runtime version 5.1.50918.0**.

The first step is to uninstall any previous Silverlight Runtime you may have and install **Silverlight Developer Runtime version 5.1.50918.0**.

:::note
Silverlight automation only works with the **Developer Runtime** version installed.
:::

To automate windowless Silverlight applications you need to activate the Extension for Silverlight. The simplest way to install the bridge extension is by opening Studio, navigating to **Tools** > **UiPath Extensions**, and selecting **Silverlight** > **Install**.

You can also install the UiPath Extension for Silverlight by using a command prompt opened with administrator rights, and running one of the following commands:

* `C:\Program Files\UiPath Studio\v8\UiPath\SetupExtensions.exe /silverlight`
* `C:\Program Files\UiPath Studio\v8\UiPath\slinject.exe /install` - This command displays more info in the console.
* `C:\Program Files\UiPath Studio\v8\UiPath\slinject.exe /uninstall` - This command uninstalls the extension. This also removes any extension entries in the **Control Panel Add/Remove Programs** section.

Note that in all cases administrator rights are required. If UAC is disabled `SetupExtensions.exe` might fail silently (at least in older versions of Studio).

Windows auto-update can silently update the Silverlight runtime. It is recommended to clear the **Enable Microsoft Update** option in the last step of the Silverlight installer wizard or configure Silverlight updates using:

`C:\Program Files (x86)\Microsoft Silverlight\5.1.50918.0\Silverlight.Configuration.exe`

You can check the windowless parameter using the UiExplorer tool as follows:

* Search for the `<param name=”windowless” />` tag under the corresponding `<object />` element.
* Use the **DOM Explorer** in Internet Explorer (press F12 to open it).