Scriptcat is a user script manager and browser extension designed to install, execute, and manage custom JavaScript scripts to modify website behavior and extend browser functionality. It features a JavaScript sandbox environment that provides specialized APIs for storage, cookies, and system notifications, alongside a cloud-synced script repository to keep subscriptions and configurations consistent across multiple devices.
The project includes an in-browser script editor for writing, testing, and debugging code directly within the browser. It also incorporates a cross-domain request engine that enables HTTP requests to bypass standard browser security policies to exchange data with external domains.
The system covers a broad range of capabilities including browser automation via recurring task scheduling and background script execution, web page customization through context injection, and comprehensive script lifecycle management such as bulk importing and version control. It provides data persistence through local, tab-scoped, and synchronized storage, as well as security controls for domain-based blocking and permission management.