- Drag open a zoom window in the image below to zoom in.
- Click on the image to toggle between Mandlebrot and Julia mode.
- Adjust parameters for fun!
- Use the history thumbnails in the lower pane to browse your zooming history.

FRACTEST! is a complete, working fractal generator implemented in javascript and HTML 5. No data is sent to or from the server in generating the fractal images.

FRACTEST! was originally authored by Daniel McFeeters in 1998, as a DOS program written in Turbo Pascal. In 2011, Daniel McFeeters re-wrote FRACTEST using javascript, as an experiment in programming with the HTML 5 canvas. Amazingly, the javascript implementation in many modern browsers is fast enough to produce some nice results, so this software has grown out of the experiment.

FRACTEST! is now licensed under the MIT Open Source License, allowing anyone to extend this fractal generator with new formulas.

*The following is excerpted from documentation that I wrote for my old
DOS fractal generator when I was 14 years old, which this simple
program is based on.*

FRACTALS are mathematical designs that have smaller copies of the same basic design repeated within themselves. You can zoom in infinitely. There are many, many different types of fractals and about as many different ways of making them.

There are fractals in nature. Notice a fern frond, for example. Notice how the fronds have leaflets coming off the main stem. These leaflets have even smaller leaflets coming off of them. Although this does not repeat itself infinitely, it is one good example of a natural fractal.

One type of fractal generated by FRACTEST is the *Mandelbrot*
fractal. The *Mandelbrot* fractal was named after
Benoit Mandelbrot, who
invented the name "Fractal". Another fractal that is very closely
related to the Mandelbrot fractal is the *Julia Set* Fractal. In fact,
these fractals are so closely related that any place on the Mandelbrot
fractal represents a Julia set fractal! The Julia set fractal will
look very similar to the place in the Mandelbrot fractal that it was
taken from!

FRACTEST makes it easy to see this relation between the Mandelbrot and Julia set fractals. Simply click a place in the Mandelbrot fractal to see it's corresponding Julia set fractal. Really, it's hard to understand and believe this until you try it yourself. Just play with the program. Experiment! Have fun!!!

Here is a very abbreviated explanation of the data. The first character
indicates the fractal type. (i.e. Mandelbrot or Julia set) When a Julia set
fractal is being displayed, the *complex constant* is given. This number tells
where in the Mandelbrot set the current Julia set was taken from. The X1, Y1
coordinates indicate the upper left-hand corner of the screen, while the
X2, Y2 tell where the lower right-hand corner of the screen is. "MAX" is,
basically, the quality of the fractal image. (i.e. The higher MAX is,
the more black area is filled with color).