CheerpJ is a WebAssembly-based Java Virtual Machine and distribution of OpenJDK for modern browsers.
🎯Broad Compatibility – Supports Java 11, Java 8 and earlier. Java 17+ coming in 2025.
🖥️Rich UI Support – Runs Swing, AWT, Oracle Forms / EBS and most frameworks in the browser.
🔒Secure & Isolated – Runs fully within the browser sandbox, with no access to the host system.
🧰Full System Integration – Clipboard, networking, file access, customer native methods.
Not sure where to start?
Get Started Based on Your Role
Build with Java & WebAssembly
on modern browser.
Improve accessibility and eliminate
dependency on legacy Java setups.
Reduce rewrite costs and modernize
Java apps without code changes.
CheerpJ: The JVM for Modern Browsers
The main CheerpJ tool for developers. A JVM / OpenJDK distribution in JavaScript and WebAssembly. Runs full Java applications and libraries in the browser.
Use Cases:
🖥️Modernize legacy Java Desktop applications
📱Develop Web Apps with Java components
🎓Java educational platforms and training apps
🛠️Browser-based deployments of legacy internal software
An end-user tool to run Java Web Start apps in Chrome or Edge – without installing Java locally. Perfect for legacy enterprise applications.
Use Cases:
🧾Launch .jnlp files in modern browsers
🏢Replace deprecated Java Web Start workflows
🧪Scientific and technical software delivery
🌐Support your enterprise migration to OpenJDK
An end-user tool to run Java Applets on modern browsers. Works instantly on Chrome or Edge, no code changes required.
Use Cases:
🧱Access Applets onlegacy websites
💹Financial/trading platforms with applet UIs
🎓Educational tools, and scientific simulations
🌐Support your enterprise migration to OpenJDK
Not sure where to start? Find the right tool for you.
We’re building the future of Java in the browser. CheerpJ is an actively developed technology with an ambitious timeline for 2025 and 2026. Here’s what’s coming:
| Feature | Availability | Status |
|---|---|---|
| Java 8 Support | Available | 🟢 Released |
| Java 11 Support | Available | 🟢 Released |
| Mobile Support | Available | 🟢 Released |
| WebAssembly JNI Modules | Available in preview (on demand) | 🟢 Nightly Builds |
| Java 17 Support | Late 2025, in preview from May 2025 | 🟡 In Development |
| JavaFX Support | Planned | 🟡 In Development |
| Java 21+ Support | 2026 | 🟡 In Development |
A superb extension with great customer support! We have an large, extensive applet that displays automated weather reports from commercial aircraft that is used by weather services world-wide. Thanks to CheerpJ we can now run it again in a browser (chrome). The CheerpJ version is FAST, able to display 800,000+ wind barbs in just a couple of seconds. We’re very happy indeed.
Fantastic job. My large JAVA applet for a visual interactive discovery of derivatives and integrals of vector fields had been used all around the world for almost 20 years — then the browsers effectively killed it by withdrawing support for JAVA. I had not been able to rewrite it as a freestanding JAVA main program. So happy when I discovered CheerpJ in the spring. So many happy students, instructors, and folks from everywhere who just to play and discover!
Matthias Kawski
This is great! I had a set of online “animated diagrams” as Java applets since about 1999. Over the years, support for Java in browsers has disappeared due to security concerns. Now I can see my old applets again.
Craig Reynolds
Simply amazing simplicity and effectiveness. Very useful with old switches that only have a Java Applet interface and other similar appliances. Great job!
Gianluca Bonetti
The Java Applet I am using looks and behaves very similarly under CheerpJ on a modern computer, vs an ancient computer with an old browser that actually runs Java applets. Performance is good, too. Five stars!
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
Discover how to modernize and improve access to your legacy Java applications with CheerpJ.
Schedule a free demo with our team to learn how CheerpJ can help address your Java requirements.
Fill in the form or book a demo directly here
English (UK) 
日本語