Greasemonkey
Greasemonkey is a browser extension that allows users to install and run custom JavaScript scripts to modify the appearance and behavior of web pages. It enables developers and users to automate tasks, enhance functionality, or fix issues on specific websites by injecting user scripts directly into the page. Originally developed for Firefox, it has inspired similar tools for other browsers, empowering users to personalize their web experience.
Developers should learn Greasemonkey when they need to customize or automate interactions with websites without requiring server-side changes or browser modifications. It is particularly useful for web scraping, adding features to existing sites, testing UI changes, or creating quick fixes for personal use. For example, it can be used to remove ads, auto-fill forms, or integrate data from multiple pages into a single view.