CheerpJ, a Java to JavaScript compiler, now available for download

Stefano De Rossi
Jun 21, 2018 · 2 min read

(originally published on September 28, 2017)

We are glad to announce that after a very intense summer of development and collaboration with our many Early Adopters, the first beta of CheerpJ, a Java compiler for Web applications, is now available for download.

What is CheerpJ?

CheerpJ is a solution to enable unmodified Java applications and libraries to be converted into JavaScript and executed client-side on any browser.

CheerpJ can be used to:
1) Convert full Java applications to HTML5/JavaScript, including Java Swing clients.
2) Develop JavaScript libraries in Java, and integrate them in web applications.
3) Convert Java applets and Java Web Start applications into HTML5 so they can run on modern browsers.

Compared to other solutions such as TeaVM and GWT, CheerpJ is compatible with 100% of Java, including reflection and dynamic class loading, and doesn’t require any modification to the source code to do so. CheerpJ is also compatible with 100% of the Java SE runtime environment. As such, it is the only solution that allows existing, unmodified Java applications to be executed on any web browser, with no server- or client-side requirements.

Download and get started

You can download CheerpJ beta for Linux, Windows and macOS at this address:

Please be aware that the Linux version is known to be more stable and better performing than the Windows and macOS, so we would recommend you to try that first if possible. The documentation for CheerpJ is a work in progress, and will be updated mainly throughout September and October. You can find it here.

You are welcome to get in touch with bug reports, feature requests and any other issues on the following channels:
1) Developers Mailing List: please join our developers mailing list at!forum/cheerpj-developers
2) GitHub: you can file any bug report
3) Gitter: feel free to drop us a line at

You are welcome to use this beta version of CheerpJ for any non-commercial reason, including technology evaluation. We expect to be releasing several beta versions over the next weeks, with general availability expected for November. To use CheerpJ for commercial reasons, please get in touch at You will be welcomed to join the many early adopters that already use CheerpJ.

More information

More information on CheerpJ, as well as several demos, can be found on our main website at as well as on our announcement blog post.

For more information, drop us a line at or at for sales enquiries. Follow us on twitter (@leaningtech) and visit to receive all our updates.


Leaning Technologies' Blog - everything Cheerp, CheerpJ, compile-to-JavaScript and compile-to-WebAssembly

Stefano De Rossi

Written by


Leaning Technologies' Blog - everything Cheerp, CheerpJ, compile-to-JavaScript and compile-to-WebAssembly

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