Jarfix for Windows

  • Free
  • In English
  • V 3.0.0
  • 3.6
  • (357)
  • Security Status

Softonic review

Cathy Buggs
Cathy BuggsUpdated a month ago

Free lightweight .jar association program

Jarfix is a free tool that is useful for Java developers and others who frequently run .jar files but find that other programs are hijacking the extension. Jarfix is a secure, lightweight, easy-to-use and completely free solution for when your PC does not run your Java files when opening items with the .jar extension.

What do I open a .jar file with?

A JAR is a package file format that is commonly used to aggregate and share multiple Java class files and their associated metadata and resources. JAR files are archive files that include a Java-specific manifest file. They are built on the ZIP format and typically have .jar file extensions.

The Java Runtime Environment combines with the Java Development Kit and the Java Virtual Machine to create a powerful trio of Java platform components for developing and running Java applications. After installing the Java Runtime Environment for the first time, .jar files should be assigned to and executed (opened) by the javaw.exe program when all is in working order. 

What is Jarfix?

Jarfix is a simple and useful program that's free and easy to download and install. The software helps recapture .jar association with the Java Runtime Environment. It requires a Windows-based operating system to work (95/98/ME/NT/2000/2003/2008/XP/Vista/7/8/10) but it is not available for Mac. If you do not have Java Runtime Environment on your machine, Jarfix will tell you where you can download it.

Jarfix is an uncomplicated program that is less than 1MB in size. Alternatives to Jarfix include 1Jar and Java Launcher.

It's a reality that .jar files can sometimes be a pain. They can just randomly start to not open or to not let you edit, change, or move them. Many developers consider .jar files some of the worst files to handle, even though it is one of the most common ways of packaging Java class files.

Most developers and others have to work with .jar files every day and are therefore familiar with the kinds of problems they can cause. Because of this, many developers would benefit from knowing about Jarfix, in case some detail goes awry.

Typically, if you double click on a .jar file and your Java application does not start, a common root cause is that your .jar association has been stolen by another program. Because .jar is such a common file extension, multiple programs can hijack the extension, resulting in .jar files being opened by the wrong program when you try and run them. This can happen even if the file type is already associated with a program.

Many zip/unzip programs highjack .jar files because a jar is stored in the .zip format. When you double click on a .jar, a different zip/unzip program might try to open the file, other than javaw.exe, because the pack program ignores meta information stored in .jar.

File connection problems can also occur if you are using a free OpenJDK without an installer.

How do I repair a .jar file?

Some developers prefer to reinstall the Java Runtime Environment or fix the Windows Registry manually each time this problem occurs. A much simpler solution, however, is to use Jarfix to repair these faulty .jar files and re-associate them with the Java Runtime Environment. This lets you run your Java files and execute your JavaScript as expected.

Running Jarfix is easy. After downloading the program, you can simply double click on it to automatically run the program and restore the .jar association with javaw.exe. A pop-up will appear that says 'The .jar suffix (Java Archive) has been registered successfully. You can execute Jar-packaged Java applications by a double click.

This message indicates that the .jar files on your computer have been fixed. You should no longer have any issues opening up .jar files. Jarfix will also set a Java icon for your .jar files.

Jarfix can also be run as an .exe, similar to any other executable on Windows. Doing this will solve the problem with your .jar file and re-associate the file extension to the correct program.

By default, Jarfix fixes the problem without any additional parameters. However, there are a few optional parameters available if you want to customize the behavior of Jarfix. These include opening the help file, running processes silently (without dialog), running the program with elevated permissions, and fixing association for one user profile or the entire PC at once.

A common use of Jarfix is to fix Optifine as well, which sometimes fails to open correctly. Some users report that when trying to boot Optifine, it will seem to open briefly before closing again. Jarfix can solve this issue by restoring the JAR file association.

Is Jarfix EXE safe?

Downloading Jarfix from a reputable source ensures that it is a safe program to use on your PC. Jarfix is not a virus. It's a lightweight program that has a small memory footprint and low CPU usage.

Easily fix highjacked .jar files

Despite the fact that it is one of the most common ways of packaging Java class files, .jar files can be annoying to manage. From refusing to open to not permitting you to edit, change or move them, many Java developers get frustrated when .jar files refuse to behave as expected.

Jarfix is a simple solution for developers and others who frequently run .jar files and find they are being highjacked by other programs. 


  • Lightweight and free to download
  • Small memory footprint and low CPU usage
  • Less than 1MB in size
  • Simple to use
  • Sets a Java icon for your .jar files
  • Optional parameters to customize program behavior


  • Not available on Mac
  • Optional parameters require using CLI or knowing how in Windows
  • Doesn't always fix the problem
  • Fixing .jar extension can be done in Windows natively

Older versions

Program available in other languages

Jarfix for PC

  • Free
  • In English
  • V 3.0.0
  • 3.6
  • (357)
  • Security Status

User reviews about Jarfix

  • Trebuchet

    by Trebuchet

    Worked instantly once I ran it. I'd been struggling without success to get two Java apps running for three days. 💜

  • Stupid Jaosn

    by Stupid Jaosn

    uh, jar files didn't work before, but they did start working after i installed it, so that's pretty neat.

  • jl

    by jl

    I downloaded it and guess what? Error launching

  • me !

    by me !


  • Jack Adam

    by Jack Adam

    Jarfix is a very useful software tool especially for us Java developers because whenever I want to run .jar files other programs are trying to hijack  More


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Laws concerning the use of this software vary from country to country. We do not encourage or condone the use of this program if it is in violation of these laws.