I just finished a simple online (MIT-licensed) Mandelbrot zoomer web app:
https://charto.github.io/fracts/

It has a few unusual features, at least for a JavaScript Mandelbrot app:

- Renders using WebGL
- Uses arbitrary precision and perturbation to allow zooming deeper than double precision normally allows.
- Stores the orbit state of every pixel during rendering, so it keeps iterating while the image changes.
- Reasonably interesting coloring using distance estimate, binary decomposition and period domains.

You can also bookmark a particular view and share a link:
https://charto.github.io/fracts/?imag=0.ab9aa4e89d1d51e72345c7ccf802c&real=-0.8714285e9d2faafe6c911ff90f7c4&zoom=-56.75
(takes a while to render).

Another special thing is the JavaScript loader. You can clone the Git repo and run serve.bat (works on Linux, OS X and Windows), and open localhost:8080 to see the app. It's written in TypeScript, but you don't need to install anything to develop locally.


Linkback: https://fractalforums.org/programming/11/mandelbrot-deep-zoomer-using-perturbation-and-webgl/3492/