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CheerpJ Applet Runner

Run Java applets without installing Java

Users80KCurrent public install base

Rating4.5Store average score

Reviews284Public review volume

Manifest versionV3Extension platform version

7-day growth0Net users gained this week

7-day growth rate0%Relative weekly velocity

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4.54

Latest

4.54

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2026年7月13日2026年7月19日

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Version2026.3

ManifestV3

Size121MiB

Languages1English

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Overview

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CheerpJ Applet Runner - Run Java applets without installing Java

With the CheerpJ Applet Runner extension, you can run legacy Java Applets on modern browsers without a Java plugin or a Java installation.

Using the CheerpJ Applet Runner is simple. Just install and pin the extension. Next, visit your Applet-based website, click the extension icon in the upper-right corner of your browser, and then press the 'Enable' button in the popup. Once enabled, the extension is activated for the current domain, and Applets will start automatically if they are present.

This extension works by 'converting' the Java Applet to WebAssembly and JavaScript on the fly. It is private and secure, runs fully client-side (i.e. it does not contact any server), and does not collect any data or analytics at all. All your data, as well as your application are kept within the boundaries of your browser.

This extension, developed by Leaning Technologies, is based on CheerpJ, a JVM/JRE replacement for modern browsers. More information on CheerpJ are available at https://www.cheerpj.com.

This software is free to use for non-business purposes on public-network Applets. For any other use, such as internal network applets, or if you are a company or public-sector organisation and would like to license CheerpJ, please get in touch with [email protected].

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Store average score4.5Chrome Web Store aggregate rating, including ratings without synced review text

Synced text average4.5Average computed only from synced review bodies

Reviews with text175Synced review bodies

Total ratings / reviews284Chrome Web Store public rating/review count

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AI product read

Run legacy Java applets in modern browsers without installing Java by converting them to WebAssembly/JavaScript on the fly

Modern browsers dropped Java plugin support, making legacy Java applet-based websites inaccessible. This extension replaces the need for a Java plugin by providing a WebAssembly-based JVM that runs Java applets entirely client-side in the browser.

User installs and pins the extension, visits a Java applet-based website, clicks the extension icon and presses 'Enable' for the current domain. The extension then detects applet/object/embed tags, replaces them with CheerpJ WebAssembly containers, and runs the Java code entirely client-side using an embedded JRE (Java 8). Licensed users get enhanced functionality via an initToken passed to the runtime.

Target users: Users needing to access legacy Java applet-based websites / Organizations with legacy internal Java applications / IT administrators deploying Java applet access via Group Policy / Users of enterprise/internal tools that rely on Java applets

The store description was truncated, so the full licensing terms are not visible from the store listing alone
The exact feature differences between free and paid tiers are not fully determinable from the source - the initToken is passed to CheerpJ runtime but its effect is in the minified cj3.js
Some binary files (WASM modules, JRE JARs) cannot be inspected for additional paid feature logic

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敏感权限：declarativeNetRequestWithHostAccess
扩展能力较强：scripting、activeTab、storage

Publisher

Leaning Technologies Ltd

Stefano De Rossi

Email: [email protected]
Phone: +447754845539
Address: 3rd Floor, 207 Regent Street London W1B 3HH GB

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