What is simulang?

Simulang is a command line tool for writing and running scripts that control desktop applications on your computer: moving the mouse, pressing keys, taking screenshots, and clicking on-screen elements. Scripts are written in JavaScript or TypeScript and run directly, with no separate compilation step needed. Under the hood, Simulang relies on a companion library called simulang-js, which taps into macOS accessibility and screen recording features so a script can understand what is currently on screen and act on it. Before first use on macOS, you run a setup command that walks through granting three system permissions: Screen Recording so it can see the screen, Accessibility so it can interact with buttons and windows, and Input Monitoring so simulated key presses and mouse clicks actually reach the app being automated. If a script does nothing or screenshots come out blank, missing permissions are almost always the cause, and rerunning setup usually fixes it. On Windows, there is no equivalent system prompt, but a downloaded file may get blocked by security software on first run, and scripts targeting apps that require elevated permissions need the terminal itself to be run as administrator. Some scripts can also call OpenRouter, a service offering access to various AI models, for tasks where the script needs an AI to look at a screenshot and decide what to click or type next. Simulang also ships an add-on for Claude Code, Anthropic's AI coding assistant, so Claude can learn how to write Simulang scripts once the add-on is installed. The tool runs on both macOS and Windows, works as a one-off script runner or as an interactive session in your terminal, and is released under the MIT license.