How does CheerpJ Applet Runner work?

The CheerpJ Applet Enabler Extension works by converting the Java Applet on the fly through CheerpJ.js, a minimal Java-bytecode-to-JavaScript compiler, and linking it to the CheerpJ runtime environment.

The compiler runs directly on your browser and doesn’t transmit your applet or the URL you are visiting to any external server.

The CheerpJ Applet Runner is not a plugin, and therefore does not pose any security threat, unlike the Java plugin.

Is any information sent to the cloud by the CheerpJ Applet Runner?

No, 100% of code execution is happening locally on the JavaScript engine of your browser. We do not collect information on the web pages you are visiting, or any logs from the extension.

Can I report applets that are not working?

We encourage everybody to file a bug report either through the extension, or as a GitHub Issue.

Is the CheerpJ Applet Runner free?

The CheerpJ Applet Runner can be used freely with no restriction on any publicly available, free Java applet.

If you want to use the CheerpJ Applet Runner within a private network, or for other commercial purposes, please get in touch with us at