Run your Java Client in a web browser with CheerpJ

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

CheerpJ 2.3 is now available. Check it out! Release notes here.

What is CheerpJ?

CheerpJ is the only solution to convert and migrate existing Java client applications to HTML5, including Swing clients, Java Applets, and Java libraries.

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;

Our Clients

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Try CheerpJ

Several demos available including a CheerpJ in-browser fiddle.

Get CheerpJ

Download CheerpJ and test it with your Application.

License CheerpJ

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

Developers Area

View documentation and begin compiling your first Java into JavaScript.

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.

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