Violentmonkey is a mature, open-source browser extension for managing and executing userscripts across Chrome, Firefox, Edge, and other WebExtensions-compatible browsers. The extension provides a full lifecycle for userscripts: installation from URLs or files, automatic updates, syntax-highlighted editing (via CodeMirror 5), per-script configuration, and a dashboard for bulk operations. Its architecture comprises a background service worker (MV3) or background page (MV2), content scripts injected into web pages (with separate realms for page-level GM API execution and content-level bridge), a popup interface, an options dashboard, an installation confirmation page, and an offscreen document for cross-origin requests under MV3. The system integrates multiple sync backends (Dropbox, Google Drive, OneDrive, WebDAV, S3-compatible), supports i18n with 30+ locales via Transifex, and includes custom build tooling for multi-browser packaging. While the core domain is userscript management, the codebase demonstrates sophisticated patterns for secure script injection, anti-spoofing (safe globals), reactive settings, and concurrency-limited storage operations.