shrinksafe.jar requires js.jar (Rhino) in the same directory. Usage: java -jar shrinksafe.jar somescript.js > minifiedscript.js There is a build-time version dependency between shrinksafe.jar and js.jar. Shrinksafe must be built and used with a particular version of Rhino. To build, run build.sh in this directory. Mozilla Rhino is licensed under MPL 1.1 (see LICENSE) and is available from http://www.mozilla.org/rhino. shrinksafe.jar is known to work with these Rhino versions: - 1.7R1 This version of ShrinkSafe will be incompatible with Rhino 1.7R3 and beyond due to changes in the Rhino API.