Emscripten is a toolset which allows compiling C/C++ into JavaScript. If that does not scare you, read further. Emscripten used to work like a compiler-wrapper around gcc/g++/clang, and other tools, and doing that now is still possible, via a package called "emscripten" (not available at SBo). However, since the ambitions of the authors began to grow, more and more tools were becoming part of the Emscripten toolset, and it became more and more unwieldy installing all of them by hand. This package, emsdk, is a set of "blessed" shell scripts to do just that in a standardised fashion. It might be compared to an Android SDK manager, or MinGW installer. Activate it by sourcing /etc/profile.d/emsdk_env.sh , or run individual commands by emsdk