User JavaScript and CSS is a free Chrome extension developed by tenRabbits. This add-on falls under the category of Browsers and specifically the subcategory of Add-ons & Tools. With this extension, users can inject their own JavaScript or CSS rules onto any website they visit.

One of the main features of User JavaScript and CSS is its instant execution, allowing users to see the changes they make in real-time. Additionally, the extension supports custom library inclusion, providing users with even more flexibility in their code. The URL masking feature is another useful tool, enabling users to apply one script or CSS rule to multiple pages.

In terms of updates, versionintroduced a function for naming rules and updated translations. Versionupdated all extension libraries to their current versions. Versionfixed an error in the console and improved the domain getter from URLs. The extension also received updates to Ace Editor and jQuery. Other versions included bug fixes, feature enhancements, and updates to various libraries.

User JavaScript and CSS is a powerful extension that allows users to customize websites with their own code. Whether it's adding functionality or modifying the appearance, this extension provides the tools necessary to make personalized changes to any webpage.