4B Pen is in public beta

Most design tools stop at the picture. You draw the screen, hand it off, and hope the app looks like it. 4B Pen is for the people who want to take it all the way: from a sketch to a live product, without learning git, build tools or hosting first.

Design, build, deploy ​

4B Pen is a desktop app with three steps in its Run menu.

• Design on a real canvas, with pages, layers, auto layout, components and variables. It opens your .fig files.
• Build turns the design into a working app in your project folder, with your own coding agent doing the work.
• Deploy puts it on the web, on Cloudflare's free plan, in one click.

Bring your own agent ​

Claude Code, Codex, Gemini CLI and other agents run in 4B Pen's built-in terminal, with your own subscription. Select a layer and your agent sees exactly what you mean: its size, colors and layout, read straight from the canvas. 4B Pen never charges for AI.

Your files stay yours ​

Every project is a folder on your computer. 4B Pen works offline, needs no account, and sends detailed usage stats only if you say yes.

Free on your computer, forever ​

Everything that runs on your computer is free. Later we'll add Cloud, for sync and share links, and Team, for designing together in real time. You can join the waitlist.

It's a beta, so expect rough edges. Download 4B Pen, make something small, ship it, and tell us what got in your way.