Greasemonkey is a Mozilla Firefox extension that allows users to install scripts that make on-the-fly changes to web page content. Developed by Anthony Lieuallen, Aaron Boodman, Johan Sundström
License: Open Source
Greasemonkey is a versatile userscript manager that allows extensive customization across various websites, while F.B. Purity focuses specifically on enhancing the Facebook experience by removing ads and unwanted content.