Best online Java decompiler — decompile JAR and CLASS files to source

Online JAR decompiler in the browser

Drop a Java archive and browse every class as source. The decompiler reconstructs methods, fields, generics, enums, lambdas, and inner classes from JVM bytecode. Use it to inspect a library, recover lost source, or review a build without a desktop reverse-engineering toolchain.

CLASS file decompiler

Open a single .class file the same way. decompiler.cc maps bytecode back to Java, and when Kotlin metadata is present the output is Kotlin-aware, so Android and server artifacts stay readable without a local install.

Why decompiler.cc

Parsing and decompilation run locally in a web worker instead of a remote decompiler service. Compare two JARs to see added, removed, and changed classes, search quoted string literals, and follow method call traces — free, with no account.

Decompile Java bytecode to source

Java compilers emit bytecode inside class files and JAR archives. A decompiler reverses that step: it reads the constant pool, attributes, and instruction stream, then emits Java you can search and compare. decompiler.cc does this entirely in the page.

How to decompile a JAR online

• Free browser Java decompiler — no install, no account
• Private: decompile JAR and CLASS files locally in a web worker
• Compare two JAR versions and highlight added, removed, and changed classes
• String explorer for quoted Java literals
• Method call traces across the archive
• Kotlin-aware output when metadata is present
• Works in modern browsers on Windows, macOS, Linux, and ChromeOS

1. Open https://decompiler.cc
2. Drop a .jar or .class file
3. Select a type in the tree and read decompiled Java source
4. Optional: load a second JAR to compare, scan strings, or open a call trace

FAQ

What is the best online Java decompiler?

decompiler.cc turns .jar and .class files into readable Java source in your browser. Decompilation runs on your device, with JAR compare, string search, and call traces in the same tab — no JD-GUI, CFR, Fernflower, Procyon, or JADX install.

Does decompiler.cc upload my JAR or CLASS files?

No. Decompilation runs locally in a web worker. Bytecode is not sent to a remote decompiler API to recover source.

Can I decompile Kotlin or Android JARs?

Yes. When Kotlin metadata is present, classes decompile with Kotlin-aware output. Standard Java bytecode from Android libraries decompiles like any other JVM class.

Is the Java decompiler free?

Yes. decompiler.cc is free to use in the browser — no account and no install.