WebAssembly
WebAssembly is a new standard for a compilation target that is quickly growing in popularity, and not just on the web. It offers portability to run anywhere with near-native speed: web browsers, cloud servers, embedded devices, plugins, blockchains, and more. Also, it allows different languages to interoperate in a convenient format, and it is secure and verifiable before execution.
There is ongoing work to add targeting support to the compiler and the standard library, making it easy to write a Crystal program that can run anywhere and accepts WebAssembly. The Crystal 1.4.0 release shipped with the initial experimental implementation, with most of the standard library already working.
Please refer to issue #12002 for an up-to-date progress status.