Compatibility

What runs in the browser with CheerpJ 4.2, what is fully supported, and how it behaves in enterprise environments.

CheerpJ 4.2 is a full Java Platform for the Web Browser. It includes a Java Virtual Machine, a Java Runtime Environment, and a system virtualization layer, implemented in WebAssembly and JavaScript and built on OpenJDK.

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View detailed compatibility

Application Types

✔️ Java Swing applications
✔️ Java AWT applications
✔️ Java Applets
✔️ Java Web Start (JNLP)
✔️ Oracle Forms and Oracle EBS frontends

UI and Graphics

✔️ Standard Swing/AWT widgets
✔️ Multiple windows within the application UI
✔️ Typical enterprise UI workflows (forms, tables, dialogs)

Runtime and Java versions

✔️ 8, 11, 17 (preview)
✔️ Java bytecode execution in the browser
✔️ Full Java runtime delivered client-side (WebAssembly-based)
✔️ Use for long-running applications that are difficult to rewrite

Typical Enterprise Use Cases

Enterprise teams use CheerpJ to modernise and deliver Java applications in browser-native environments.

Modernise Oracle Forms and EBS

Deliver Oracle Forms and Oracle EBS applications in modern browsers without rewriting the frontend.

Replace Java Web Start

Eliminate desktop installs and JNLP distribution.
Run existing applications directly in the browser using standard web deployment.

Replace Java Applets

Replace browser plugins with a browser-native runtime.
Deploy legacy applets as standard web applications without requiring a client-side JVM.

Deliver to Locked-Down Endpoints

Deliver internal Java applications to:

Locked-down corporate endpoints
Chromebooks
Mobile browsers

Without installing a JVM.

Java and Runtime Compatibility

CheerpJ 4.2 provides a browser-based JVM and JRE built on OpenJDK. It executes Java applications at bytecode level without requiring source code changes.

Java Language and Bytecode Compatibility

Java Language Coverage

Full Java language compatibility (including reflection and dynamic constructs)
Proxy classes
Custom class loaders
Encrypted and obfuscated bytecode

Application Packaging

.jar
.war
Applets
Web Start

Runtime Capabilities in the Browser

Networking

HTTP(S)
TCP support within browser constraints

File System

Virtualised file system
Direct access where supported by browser APIs

Desktop Features

Clipboard
Printing
Audio

Typical deployment model

Codebase unchanged

Existing Java application codebase remains unchanged

Runtime in browser

CheerpJ provides the Java runtime inside the browser

Backend unchanged

Backend services and databases remain unchanged

Standard security model

Standard browser security and access controls apply

Deployment options: On-premise or controlled enterprise environments.

Architecture overview

Existing Java applications run unchanged, with CheerpJ providing the Java runtime inside the browser using WebAssembly.

Scenarios That May Require Technical Review

Most enterprise Java applications deploy without modification.

The following integration patterns require architectural review prior to deployment.

Tight operating system integration

Direct process execution, local system services, or OS-level hooks require architectural adjustment.

Extensive JavaFX usage

JavaFX support is partial. Applications heavily dependent on advanced JavaFX features should be reviewed.

Direct hardware access

Access to USB devices, serial ports, smart cards, or proprietary hardware requires integration via web-compatible APIs.

Native binaries or JNI dependencies

Applications that rely on platform-specific native libraries require review to determine a browser-compatible approach.

Custom low-level networking protocols

Applications using non-HTTP protocols or raw socket models may require gateway or proxy adaptation.

Our engineering team can review these patterns and provide a recommended deployment approach.

Request a compatibility assessment

Detailed Compatibility Specification

The following tables summarise CheerpJ 4.2 compatibility status.
All statuses reflect the current technical datasheet (version 4.2).

1. Java Version Support

Java Version	Status	Notes
Java 8	Full support	Production supported
Java 11	Full support	Production supported
Java 17	Partial	Production supported
Java 6	Supported via LTS	Available on respective LTS versions
Java 7	Supported via LTS	Available on respective LTS versions

Support for specific OpenJDK runtime versions is available on request.

2. UI Framework Support

Framework	Status	Notes
Swing	Full support	Standard Swing applications supported
AWT	Full support	Standard AWT widgets supported
JavaFX	Partial support	Review recommended for advanced JavaFX applications

Limitations – JavaFX

JavaFX support is partial. Applications heavily dependent on advanced JavaFX features or platform-specific rendering behaviour require technical review prior to deployment.

3. Class Library Coverage

CheerpJ executes Java applications at bytecode level and includes a browser-based JVM and JRE built on OpenJDK.

3.1 Java Language and Bytecode

Area	Status	Notes
Java language compatibility	Full support	100% Java language compatibility
Reflection	Supported	Works without rewrites
Proxy classes	Supported
Dynamic constructs	Supported
Custom class loaders	Supported
Encrypted / obfuscated bytecode	Supported

3.2 Core and Runtime Libraries

Library Area	Status	Notes
Core class libraries	Supported	Based on OpenJDK
Networking – HTTP(S)	Supported	Subject to browser security model
Networking – TCP	Supported	Requires an additional proxy component.
File system – Virtualised	Supported	Browser-based virtual file system
File system – Direct access	Supported	Where permitted by browser APIs
Clipboard	Supported	Via browser APIs
Printing	Supported	Browser-based printing
Audio	Supported

Limitations – Class Libraries

Because CheerpJ runs entirely inside the browser:

The Web security model applies.
Cross-Origin restrictions apply.
Direct operating system access is not available.
File system access is subject to browser capabilities.
Networking is subject to browser security constraints.

4. JNI and Native Code Support

Area	Status	Notes
JNI native execution	Not supported	Native binaries cannot execute inside the browser runtime
Platform-specific native libraries	Not supported	Requires architectural adaptation

CheerpJ executes Java bytecode in a browser-based JVM implemented in WebAssembly and JavaScript. Native binaries and OS-level libraries are not executable inside the browser environment.

Limitations – Native Integration

Applications that rely on:

Platform-specific DLLs / shared objects
Direct OS process execution
Low-level system hooks

require architectural review and alternative integration patterns.

Browser Support

Browser	Status
Chrome	Supported
Edge	Supported
Chromium-based browsers	Supported
Firefox	Supported
Safari	Supported
Mobile Chrome	Supported
Mobile Safari	Supported
Mobile Firefox	Supported

CheerpJ requires a modern browser with WebAssembly support.

Documentation

For detailed configuration and deployment guidance, refer to:

www.cheerpj.com/docs

Compatibility Assessment

Not sure about your application?

Confirm compatibility for your application.

Submit your application details, and our engineering team will provide a compatibility assessment.