User:The Transhumanist/Sandbox18

A userscript manager is a type of browser extension and augmented browsing technology that allows users to install scripts (written in JavaScript) to modify webpages as they browse them, and provides an interface to load, create, and organize userscripts. Popular userscript managers include Tampermonkey and Greasemonkey. Several host sites make repositories available for sharing scripts.

Greasemonkey
Greasemonkey is a userscript manager made available as a Mozilla Firefox extension. It enables users to install scripts (written in JavaScript) that make on-the-fly changes to web page content after or before the page is loaded in the browser (also known as augmented browsing). The changes made to the web pages are executed every time the page is viewed, making them effectively permanent for the user running the script. Greasemonkey can be used for customizing page appearance, adding new functions to web pages (for example, embedding price comparisons within shopping sites), fixing rendering bugs, combining data from multiple web pages, and numerous other purposes. Users can either write their own scripts, or collect them from the web, such as from script hosting sites like Greasy Fork.

Tampermonkey
Tampermonkey is a userscript manager browser extension for mainstream browsers, including Chrome, Edge, Firefox, Opera, and Safari. It enables users to install scripts (written in JavaScript) to modify webpages as they browse them, and provides an interface to load, create, and organize userscripts. Userscripts for Tampermonkey are available to download at OpenUserJS.org, and similar sites.