What is a User Script? Userscripts (a.k.a User Scripts, User scripts, or .user.js) are open-source licensed add-ons for web browsers, written in JavaScript, that change web pages as they are loaded.
Tampermonkey lets you customize and enhance web pages with userscripts, small JavaScript programs that add new features or modify existing ones. You can easily create, manage, run, and update userscripts on Chrome, Edge, Firefox, Safari, and Opera Next.
These scripts are oftentimes used to add some functionality to a page or to change its appearance. These are typically written in JavaScript, but can be written in other languages as well.