You know that moment when you're writing documentation, a README, or a code comment, and you think "a diagram would really help here"? And then you spend 20 minutes fighting with some bloated diagramming tool, export a PNG, realize it doesn't match your dark theme, and give up?

Meet MonoSketch.

What is it?

MonoSketch is a web-based ASCII diagram editor. You draw boxes, lines, and text — and it outputs pure ASCII art that you can paste anywhere. Code comments. READMEs. Slack messages. Config files. Terminal output.

It runs entirely in your browser. No account. No server. No data leaves your machine. Just open app.monosketch.io and start drawing.

Why it's cool

If you've ever used Monodraw on macOS, you know how satisfying it is to create clean ASCII diagrams with a proper GUI. The problem? Monodraw is Mac-only and costs money. MonoSketch is the open-source, cross-platform answer.

Here's what you get:

  • Rectangle tool — drag to create boxes with proper Unicode borders
  • Line tool — draw connections between shapes, with arrows
  • Text tool — add labels anywhere
  • Multiple border styles — thin, thick, double, rounded, dashed
  • Fill patterns — solid fills, custom characters
  • Copy as text — select your diagram and paste it as pure text

The result looks like this:

┌───────────────────┐     ┌───────────────────┐
│   Load Balancer   │────▶│    Web Server      │
└───────────────────┘     └────────┬───────────┘
                                   │
                          ┌────────▼───────────┐
                          │     Database        │
                          └────────────────────┘

That's not an image. That's text. It lives in your code. It survives copy-paste. It works in every font, every terminal, every editor. It'll still be readable in 20 years.

Try it right now

Literally just open this URL:

https://app.monosketch.io/

No install. No signup. Click the rectangle tool, draw a box, add some text, draw a line between two boxes. Done. Copy the result and paste it into your terminal. That's it.

If you want to self-host it (it's a static site, so this is trivial):

git clone https://github.com/tuanchauict/MonoSketch.git
cd MonoSketch
# Serve the built files with any static server
# Or just use the hosted version — it's all client-side anyway

Who is this for?

  • Developers who put diagrams in code comments and READMEs
  • DevOps folks who document network topologies in plain text
  • Terminal enthusiasts who want their docs to look good in a monospace font
  • Anyone tired of image-based diagrams that break, don't render in terminals, and can't be diffed in git

Any downsides?

It's still a young project — the developer is actively rewriting it from Kotlin/JS to TypeScript. Some features you might expect (like undo history or keyboard shortcuts for everything) aren't fully there yet. And there's no offline PWA mode, so you do need internet access.

But for what it does today? It's already the best free ASCII diagram editor I've found.

Links

Go draw some boxes. You know you want to. 📦