VirtualBox answers the cheap questions: is this program safe, does the new system suit me, how does this code behave on another distribution. Free, open source, hosted on Windows, macOS and Linux, with snapshots that turn any experiment into something you can undo in one step.

Desktop virtualisation that has been the reference for two decades: run other systems on Windows or Linux at near-native speed, take snapshots before an experiment, clone a whole machine, shape virtual networks, and move files between host and guest. Free for personal use.