unattendxml

Unattend.xml, commonly called an unattend file, is an XML-based answer file used by Windows Setup to automate and customize a Windows installation. It enables administrators to perform unattended deployments by supplying configuration data that would normally be entered manually during setup.

The file is organized around settings passes, which group configuration for different stages of the deployment. Typical passes include WindowsPE (early pre-installation), offlineServicing, generalize, specialize, and oobeSystem (the out-of-box experience). Each pass contains component settings that control elements such as disk partitioning, product keys, license terms, locale, time zone, network configuration, and user accounts. Common components include Microsoft-Windows-Setup and Microsoft-Windows-Shell-Setup, among others. The structure allows precise control over what Windows does at each stage of installation and first boot.

Authoring unattend.xml is supported by dedicated tools such as Windows System Image Manager (WSIM), part of the Windows Assessment and Deployment Kit (ADK). These tools help verify schema correctness and provide prebuilt settings catalogs for different Windows versions. Unattend.xml can be placed on the installation media’s root or provided to Setup through appropriate startup parameters, enabling fully automated deployments in enterprise environments, labs, and imaging pipelines.

Security considerations include the potential exposure of sensitive data, since unattend.xml can contain passwords and product keys in plaintext. Organizations should protect the file, minimize sensitive data, and use secure deployment practices.

Related topics include Windows deployment services, imaging pipelines, and the Windows ADK.