The CheerpJ Applet Runner is a browser extension/add-on that enables Java applets without requiring a local Java installation or to install deprecated plugins. CheerpJ Applet Runner is available as:

Note that both versions are upgraded to release of 2.2 of CheerpJ.

Since Java Applets have lost support on the majority of browsers, a tremendous amount of content, particularly in science and education, is virtually inaccessible. We aim at solving this problem by providing a solution to extend the life of Java applets on modern browsers.

What is the CheerpJ Applet Runner?

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

Main project link:

Please note that CheerpJ Applet Runner extension is self packaged, meaning all needed assets will be downloaded at installation/update time. Usage of the CheerpJ Applet Runner will then only ever require users to download the actual applet content.

Using the CheerpJ Applet Runner

Please feel free to try the extension on any applet you like. Here are a few examples:

Bugs and Questions

We welcome any feedback and bug report, either through the Extension/Add-On itself (click on icon + “Report bug”) or on GitHub.

We aim at supporting as many Java applets as possible, and eventually Java WebStart applications.

More information

You can find more information on the CheerpJ Applet Runner Extension in the FAQs