Userscript

A userscript is a small computer program, typically written in JavaScript, that adds new functionality to a website or modifies its existing appearance or behavior. Userscripts are installed and run using a browser extension, such as Tampermonkey, Greasemonkey, or Violentmonkey. These extensions act as managers for userscripts, allowing users to enable, disable, and manage the scripts they have installed.

The primary purpose of a userscript is to customize the user's experience on specific websites. This can range from simple cosmetic changes, like altering fonts or colors, to more complex modifications, such as adding new buttons, automating repetitive tasks, removing unwanted elements, or integrating features from other services. For example, a userscript might automatically expand all comment sections on a forum, add a download button to a video-sharing site, or change the layout of a social media feed.

Userscripts are developed by individual users or communities and are often shared on platforms dedicated to userscript hosting. When a user visits a website for which a userscript is installed and active, the browser extension detects the match and executes the script. This execution happens on the user's local machine, meaning the changes are only visible to that user and do not affect the website for other visitors. The security of userscripts is a consideration, as they can potentially access and manipulate data on the websites they run on. Therefore, it is advisable to only install userscripts from trusted sources and to review their code if possible.