FireMonkey is described as 'Firemonkey is a totally new combined user-Scripts and user-Style manager. While it has similar functions to other user-Script managers like GreaseMonkey/Tampermonkey/Violentmonkey, and user-CSS managers like Stylish/Stylus/xStyle, there are also differences' and is a Userscript Manager in the Web Browsers category. There are six alternatives to FireMonkey for a variety of platforms, including Mac, Firefox, Google Chrome, Windows and Linux. The best alternative is Greasemonkey, which is both free and Open Source. Other great apps like FireMonkey are Tampermonkey (Free Personal), Violentmonkey (Free, Open Source), Userscripts (Free, Open Source) and Powerlet (Free, Open Source).