Fontprep is described as 'The missing font generator for Mac OSX'. There are four alternatives to Fontprep for Online / Web-based and Mac. The best alternative is Fontello, which is both free and Open Source. Other great apps like Fontprep are IcoMoon (Freemium, Open Source), fontplop (Free, Open Source) and @font-face Generator (Free).
fontplop is an OSX/macOS application which takes ttf and otf files and outputs a webfont bundle: woff2, woff, ttf, svg, and eot. It is the simpler, faster, free successor to FontPrep, which is no longer maintained.