Violentmonkey — Open Source Userscript Manager for Browsers

Introduction

Violentmonkey is a fully open-source browser extension that runs userscripts on web pages. Userscripts are small JavaScript programs that modify how websites look and behave, from removing annoyances to adding entirely new features. Violentmonkey provides a fast, clean interface for installing, managing, and editing these scripts.

What Violentmonkey Does

• Installs and runs userscripts from repositories like Greasy Fork and OpenUserJS
• Provides a built-in code editor with syntax highlighting for writing custom scripts
• Supports the Greasemonkey and Tampermonkey API for broad script compatibility
• Syncs scripts and settings across devices via cloud storage providers
• Allows fine-grained control over which scripts run on which sites

Architecture Overview

Violentmonkey is a WebExtension built with Vue.js for the UI and vanilla JavaScript for the script injection engine. Scripts are stored in the browser's IndexedDB and injected into matching pages using content scripts. The extension uses a sandboxed execution environment to isolate userscript code from the page's own JavaScript. An internal message bus connects the popup, options page, and content scripts.

Self-Hosting & Configuration

• Install from Chrome Web Store, Firefox Add-ons, Edge Add-ons, or Opera Add-ons
• Import and export scripts and settings for backup and migration
• Configure cloud sync via Dropbox, OneDrive, Google Drive, or WebDAV
• Customize injection timing, script execution order, and per-site permissions
• Build from source using Node.js and the instructions in the GitHub repository

Key Features

• Fully open source under the MIT license
• Compatible with Greasemonkey and Tampermonkey script APIs
• Built-in editor with syntax highlighting, auto-completion, and linting
• Cloud sync support across multiple storage providers
• Lightweight and fast with minimal memory footprint

Comparison with Similar Tools

• Tampermonkey — most popular userscript manager but proprietary; Violentmonkey is fully open source
• Greasemonkey — the original userscript manager for Firefox; Violentmonkey offers cross-browser support and a more modern UI
• Userscripts (Safari) — macOS and iOS only; Violentmonkey covers Chrome, Firefox, Edge, and Opera
• Stylus — manages CSS-only modifications; Violentmonkey handles full JavaScript userscripts

FAQ

Q: Is Violentmonkey compatible with Tampermonkey scripts? A: Yes. Violentmonkey supports the GM_* and GM.* APIs used by both Tampermonkey and Greasemonkey, so most scripts work without modification.

Q: Where can I find userscripts to install? A: Greasy Fork (greasyfork.org) and OpenUserJS (openuserjs.org) are the two largest userscript repositories.

Q: Is it safe to run userscripts? A: Userscripts from trusted sources are generally safe. Always review a script's code and permissions before installing, especially if it requests cross-site access.

Q: How does Violentmonkey differ from Tampermonkey? A: The primary difference is licensing. Violentmonkey is fully open source (MIT), while Tampermonkey is proprietary. Feature-wise, both are capable userscript managers.

Sources

• https://github.com/violentmonkey/violentmonkey
• https://violentmonkey.github.io