Currently, Essence itself only runs under Scheme 48 [6]. However, the generated parsers run under any R5RS [5] Scheme. Moreover, the dependencies on non-standard features of Scheme48 which Essence uses have been carefully factored out with the help of the Scheme 48 module system; making it work in any given Scheme implementation is not hard.
The Essence distribution contains three files to be loaded into Scheme 48's configuration package: interfaces.scm, packages.scm, and generator-packages.scm. To make Essence available within Scheme 48, it is always necessary to load interfaces.scm (via ,config ,load interfaces.scm). To run the generic parsers, it is necessary to also load packages.scm, to use the parser generator, generator-packages.scm.