Jar to java decompiler online

13 Best Java Decompilers for Download and Online Use for Java Developers

A quick guide to best java decompilers for the java developers offline usage and best online java decompilers.

1. Overview

in this tutorial, We’ll learn what are the best java decompilers for the java developers and what are java
online decompilers available for free usage.

For some of the developers who do not have access to download it to the development machines, they might need the help of online decompilers.

2. What is Decompiler?

When the java class is compiled and then the JVM generates the .class file for that class. That means java source code is converted into the .class file which is in the form of the byte stream.

Now the generated class file is not in a readable format. So, how to read the class file in java?

Java Decompiler converts the byte stream data into the readable source file.

Many times, you might be in the need to see the third party jars source code to debug issues.

If you do not have the right decompiler tool then you can not view the .class file in java.

By using Decompiler, you can view the source code for java built in api classes for String, ArrayList, HashSet and HashMap classes.

All java API classes are present in the rt.jar file. This file is generated by the JDK as soon as you install java on your machine.

Every java developer must have one java decompiler to become a better programmer by seeing the .class files internal code.

3. Java Decompiler Tools

If you are using only eclipse then only you need the decompiler. Because decompiler is not integrated with the eclipse. You need to add the jd decompiler to it.

But if you IntelliJ idea user, by default it comes with the inbuilt decompiler which works flawlessly.

Let us see the offline java decompiler tools and choose the best one for you.

3.1 JDProject Java Decompiler

JDProject means java decompiler project. This works on windows, unix and mac os.

JDProject is the most used java decompiler in the world by java developers because it has the support for the Eclipse IDE and offline tool as well.

This one is easy to use and supports java 1.1 onwards.

And also JD has syntax highlighting and also open multiple jars at the same time from the offline tool.

This can easily reconstruct the java source file from the any version java .class file.

Works with enums, collections, java 8 stream apis as well.

3.2 Procyon

Procyon is a java decompiler developed by Mike Strobel.

Procyon decompiler handles java language enhancements from JDK 1.5 and beyond that most other decompilers don’t. Procyon really works very well with enum declarations, annotations, java 8 lambdas and method references.

Compare to this, I suggest to use the JD project decompiler because Procyon is still a new one and still development is in progress.

3.3 Neshkov – DJ Java compiler

This is also another free decompiler tool.

DJ decompiler is windows based and support all windows operating systems till windows 10.

This is a standalone tool like the above decompilers with GUI.

The main advantage of this tool is, JDK is not needed to be installed on the machine to run this tool.

The program enables users to save, print, edit and compile the generated java code.

And also you can edit and run the code instantly using the given option as below.

3.4 Cavaj Java Decompiler

This is another java decompiler and is free software.

Cavaj Java Decompiler is a simple GUI for only for windows developers and does not provide the java

This is not available for the MAC and Unix os. So, this is not recommened for the experienced developers.

3.5 AndroChef Java Decompiler

Andochef is a windows based GUI and works with apk., dex, jar and java class-files. It’s simple and easy.

AndroChef Java Decompiler is Windows XP, Windows 2003, Windows Vista, Windows 7, Windows 8 , 8.1 and Windows 10 decompiler for Java that reconstructs the original source code from the compiled binary CLASS files.

AndroChef Java Decompiler is able to decompile the most complex Java 6 applets and binaries, producing accurate source code from it.

This decompiler works for android apk files also.

For large APK files (over 10 MB) – decompilation may take several minutes to complete or even longer, depending on the configuration of your computer and the size of the file.

To get the full features, you need to buy the licenced copy of software.

3.6 JBVD – Java Bytecode Viewer & Decompiler

JBVD provides the support for the cross platforms such as Windows, Mac and Unix environments.

A very powerful java bytecode viewer and decompiler which makes use of the javassist open source library.

This is not getting the recent updates since 2017.

3.7 FernFlower

Fernflower is the first actually working analytical decompiler for Java and probably for a high-level programming language in general.

This is still under the development.

Better to skip these type of decompiler till its full development and tested. But you can try and use it if you like. If you intellij user, then you may like this.

This is for intellij idea and used as plugin,

3.8 CFR – another java decompiler

Last but not unused one. CFT is completely written in java 6 and provides decompilation for the java modern syntax.

If you are working on java 8 then this is very good for you to get the accurate the results.

This can work with the latest java version java 9, 12 and 14 also.

The recent update is in the fen 2021 and can expect the further updates in future.

By using this command line interface, we can get the fast and efficient source codes from this.

4. Java Online Decompilers

Some of the developers do not like decompiling on the local computer rather they prefer doing it online.

Or if you want to decomiple only one class file then you may need to go the online decompilers.

But it is strictly recommended not to use online decomiples for your production code base.

if that class has the sensitive information, it may triggers the entry point to the hackers.

Some of the online decompilers list.

4.1 javadecompilers.com

This online decompier expects you to upload the .class file and select the decompiler that you want to use the from the top tools.

4.2 jdec.app

4.3 javainuse – Java Decompiler Online

A CLASS file is a compiled .JAVA file created by the Java compiler. It contains bytecode, which is binary program code that is executable when run by a Java Virtual Machine (JVM). CLASS files are commonly bundled into .JAR files, which are included in the $CLASSPATH environment variable for execution.

4.4 decompiler.com

decompiler.com online decompiler works for all of these extentions – EXE or DLL, JAR or CLASS, APK, XAPK or DEX,PYC or PYO, LUAC or LUB, SMX or AMXX.

This is kind of all in one decompiler but it is online.

You can decompiler java classes, F#, C#, android, python and lua code as well.

4.5 devtoolzone.com

5. Conclusion

As of now, we have seen many java decompiler for offline and online usage.

if you are intelliJ user then you do not need any of these because it is intergrated with inbuilt best decompiler.

If you eclipse user, Please use JDProject one because this provides the plugin for eclipse.

If you are learning java and do not use any IDE then you can use the online decompiler for your choice.

Note: Do not use the online decompier for the production classes.

Published on Java Code Geeks with permission by Venkatesh Nukala, partner at our JCG program. See the original article here: 13 Best Java Decompilers for Download and Online Use for Java Developers

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.JAR and .Class to Java decompiler

Until recently, you needed to use a Java decompiler and all of them were either unstable, obsolete, unfinished, or in the best case all of the above. And, if not, then they were commercial. The obsoleteness was typically proved by the fact that they can only decompile JDK 1.3 bytecode.
The only so-so working solution was to take the .class file and pre-process it, so it becomes JDK 1.3 compatible, and then run Jad over it (one of those older, but better decompilers).

But recently, a new wave of decompilers has forayed onto the market: Procyon, CFR, JD, Fernflower, Krakatau, Candle.
Here’s a list of decompilers presented on this site:

CFR

This free and open-source decompiler is available here: http://www.benf.org/other/cfr/
Author: Lee Benfield

• Java 7: String switches
• Java 8: lambdas
• Java 9: modules
• Java 11: dynamic constants
• Java 12: Kotlin style «switch expressions»
• Java 14: ‘instance of’ pattern match and ‘Record types’

JD

free for non-commercial use only, http://jd.benow.ca/
Author: Emmanuel Dupuy

Updated in 2015. Has its own visual interface and plugins to Eclipse and IntelliJ . Written in C++, so very fast. Supports Java 5.

Procyon

• Enum declarations
• Enum and String switch statements
• Local classes (both anonymous and named)
• Annotations
• Java 8 Lambdas and method references (i.e., the :: operator).

Fernflower

Updated in 2015. Very promising analytical Java decompiler, now becomes an integral part of IntelliJ 14. (https://github.com/JetBrains/intellij-community/tree/master/plugins/java-decompiler)
Supports Java up to version 6 (Annotations, generics, enums)

JAD

given here only for historical reason. Free, no source-code available, jad download mirror
Author: Pavel Kouznetsov

Probably, this is the most popular Java decompiler, but primarily of this age only. Written in C++, so very fast.
Outdated, unsupported and does not decompile correctly Java 5 and later.

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Free Online Java Decompiler

Upload and decompile any ‘.jar’, ‘.dex’, ‘.class’, ‘.smali’ file.
Powered by jadx.

Java Decompiler Explanation

Java is a powerful programming language that can be used to create complex software. However, its syntax can be difficult to understand and read. To make life easier, online Java decompilers are available that can help you understand and decompile Java code.

If you’re a Java developer, you’ve probably used a decompiler at some point. A decompiler is a tool that takes a compiled files e.g (‘.jar’, ‘.dex’, ‘.class’, ‘.smali’) and converts it back into source code.

There are a few reasons you might want to use a decompiler. Maybe you lost the source code for a class and you need to make a change. Or maybe you’re trying to understand how a particular class works.

There are a few different decompilers available, but my personal favorite is Unbox APK Java decompiler. It’s totally free & easy to use, and it does a great job of decompiling Java code.

If you’ve never used a decompiler before, this is a great place to start. I’m going to show you how to use online java decompiler tool to decompile a Java files e.g (‘.jar’, ‘.dex’, ‘.class’, ‘.smali’).

First, go to this link . here you will see a button named upload.

click on upload button and select the file of you choice e.g (‘.jar’, ‘.dex’, ‘.class’, ‘.smali’) which you want to decompile, once you select the file you will see your file name will appear on the upload button.

Now, Press the button on which your file name will appear, the process of java decompiler will start and you will be able to download the decompiled source code of jar file in a while.

After process has completed you will be able to see a download source code link. click the link and downloading will start a zip file. zip file contains the complete source code.

Please note: File you choose must be under 100mb. if greater then 100mb it will not process.

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