The Crystal compiler doesn't run on Windows yet. But Crystal can be used with the Windows Subsystem for Linux, a compatibility-layer for Linux executables running natively on Windows 10.
Several Linux distribution are supported by WSL and the installation instructions for Crystal are equal to that of the respective Linux distribution, most commonly Debian/Ubuntu.
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https://crystal-lang.org/docs/installation/on_bash_on_ubuntu_on_windows.html