A Browser-Based Solution To All Your Java Needs

CheerpJ can convert any Java client application into standard HTML5 / WebAssembly / JavaScript saving your business time, money and resources.

Announcing CheerpJ 3.0: find out more here

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.

Application orHTTP ServerLegacyBrowsersAll ModernBrowsers

Why CheerpJ?

CheerpJ allows organisations to extend the life of their Java applications by making them usable on modern browsers, with no change to their source code.

It supports 100% of the Java language and runtime, read-write access to the file system, networking, printing, and many other system features.

CheerpJ does not require any server-side support, as all application components (converted application and runtime) are static. Applications converted with CheerpJ can run on any modern browser, on any operating system.

CheerpJ was developed with three main use-case scenarios in mind:

Legacy Applications

The conversion of legacy Java applications to HTML5 with minimal or no effort, making them accessible from modern browsers, without a local Java installation;

Java Applets

Accessing Java Applets on Chrome, Edge, Firefox, Safari, or any other modern browser, including for mobile. You can continue using your internal or third-party Java Applet interfaces on modern IT architectures;

Java Client Migration

The migration of an existing Java client to a browser-based web application, usually by converting the business logic from Java to WebAssembly/JavaScript with CheerpJ, and rewriting the UI in native HTML;

Trusted By

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Customer Stories

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

PhET Interactive Simulations at the University of Colorado Boulder (https://phet.colorado.edu) 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…

How CheerpJ Works


The CheerpJ compiler processes your Java bytecode ahead of time, generating optimised JavaScript that can run on any browser.

CheerpJ Runtime

In parallel to your converted application, deploy a higly-optimised runtime in WebAssembly and JavaScript, keeping 100% of the execution client-side. Based on a full unmodified build of OpenJDK .

CheerpJ Java compiler

Whenever new classes are generated (e.g. through proxy classes), CheerpJ will convert them on the fly for you.

ApplicationServerCheerpJ RuntimeHTTP ServerAll ModernBrowsersBackendFrontend

Thanks to these three components, CheerpJ provides a seamless experience of executing a converted Java application on any browser, fully client-side. No plugins and no installation are required from the user.

Leaning Technologies coupled their clear ability to extend their toolset to support the ultimate software challenge with an unwavering determination to achieve the level of perfection required. After an intense but relatively short period, Blackbird was able to ship our [HTML] product to clients globally.

Stephen Streater
R&D Director, Blackbird PLC

Are you considering a project with CheerpJ?

Other Resources

Several demos available including a CheerpJ in-browser fiddle.

Download CheerpJ and test it with your Application.

With options to suit all, get started with CheerpJ today!

Search our Documentation for answers to your queries.

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