I built a Mandelbrot Set Explorer using Javascript Web Workers and HTML5 Canvas. It’s one of my favorite software projects!

Drag your mouse over the canvas to zoom in.

Iterations: 70 %

Source Code


The Mandelbrot Set Explorer is one of my favorite software projects to build. I’ve built it in Visual Basic, Java, Processing.js, and Assembly. It’s my go to project when I want to learn a new language.

The goal of the version above was to play around with the Web Workers API. This is a new feature in browsers that lets you essentially multi-thread your application. A perfect use case for multi-threading, is to perform Mandelbrot Set calculations without freezing the browser.

I initially wanted to use the Big.js high precision math library. The idea was that I could bypass the floating point limits in Javascript, allowing me to zoom indefinitely into the fractal. After trying the library however, I hit some pretty heavy CPU usage. It was simply too computationally intensive for any practical use. I ended up going back to using native floating point numbers.


I coded this entire app in about 2 hours. My biggest struggle with Mandelbrot is figuring out the coordinate system. I always have to figure out the algebra necessary to convert pixel coordinates to mathematical coordinates. I will confuse xMin and yMax, and flip the axis wrong. It requires so much mental energy to code the zooming logic.

The Web Worker API was dead simple to use. The onmessage and postMessage commands work exactly as described. I made a simple progress bar by using the HTML5 <progress> tag, and posting a special message at regular intervals from the main worker loop.

I am impressed, and will try to find more usages for web workers in future projects.

Using the Hugo static site generator made development a breeze. The hot reloading feature allowed me to iterate quickly.


A few days later, I installed Fractal XTreme, and it amazed me. Read my review here.