Which Windows 10 update added Windows Sandbox?

Windows 10 version 1903 added Windows Sandbox. Also known as the May 2019 Update and codenamed 19H1, it introduced the feature as an optional component in Pro, Enterprise, and Education editions rather than Windows 10 Home.

Windows Sandbox gives users a temporary, isolated desktop environment for testing software or opening suspicious files. It uses virtualization-based protection and is discarded when the Sandbox window closes, so changes made inside it do not normally persist to the host installation. This made it useful for administrators, developers, and cautious users who needed a disposable test area.

Version 1903 became generally available on May 21, 2019. It included several other visible changes, such as a light theme, a separated Search experience, update-pause controls, and new troubleshooting features. The Sandbox feature therefore belongs specifically to that release, not to version 1803 or the later 2004 update.

A common mix-up is treating Windows Sandbox as a full virtual machine product. It relies on Windows virtualization technology but is designed to start quickly and reset automatically, while Hyper-V provides broader tools for managing persistent virtual machines.