CheerpJ brings PhET’s free education Java simulations to the web

“The CheerpJ technology has been a true game-changer for PhET simulations."
Kathy Perkins, Director, PhET Interactive Simulations
Product Used:

PhET Interactive Simulations at the University of Colorado Boulder ( provides over 150 interactive, research-based simulations for teaching science and mathematics. The simulations are used in primary, secondary, and university education, translated into over 80 languages and provided as open (free) educational resources. PhET also partners with diverse education companies to advance STEM education worldwide.

What the project entailed

For years, as school technologies have shifted to Chromebooks and iPads, many teachers and students lost access to some of their favourite PhET simulations because these simulations were built on our legacy Java code. Therefore, they embarked on a process of re-writing these simulations in HTML5, however, this is a costly and timely process. 

By taking advantage of Leaning Technologies’ CheerpJ Java to WebAssembly compiler, PhET Interactive Simulations at the University of Colorado Boulder has developed a stopgap solution to make their Java simulations accessible via any web browser, without a local Java installation. 

CheerpJ is the only Java compiler for the Web extensively compatible with Java 8 (Tested on Oracle Forms, EBS, Swing, AWT and numerous frameworks and libraries). It converts any Java client application into standard WebAssembly and JavaScript. CheerpJ provides an automated tool for converting legacy Java applications (including Applets and stand-alone Java clients) into a combination of WebAssembly and JavaScript, so they can be integrated into modern, browser-based HTML5 web applications.

The Result

This new partnership has opened the door to enable millions of students and teachers to continue to use PhET’s legacy Java science and math simulations on a wider variety of devices, including Chromebooks and iPads.


We are extremely happy that we have been able to contribute to extending the life of an educational resource that is so valuable to hundreds of thousands of students across the world every day. This is a perfect example of how CheerpJ – being extensively compatible with Java 8 – can automatically convert large numbers of applications to HTML5 with minimal or no manual intervention.”

– Stefano De Rossi, CEO, Leaning Technologies

“The CheerpJ technology has been a true game-changer for PhET simulations. We were able to create new browser-compatible versions of 57 legacy Java simulations, restoring access at a time of great need. The PhET teacher community could not be happier!”

– Kathy Perkins, Director, PhET Interactive Simulations

What is CheerpJ?

An Enterprise-grade solution to modernise and preserve access to mission-critical Java Applications and Applets by removing the requirement for Java on the client.

CheerpJ converts Java bytecode into WebAssembly and JavaScript, so that it can run natively on modern browsers.

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