How to open .JAR files (Java archives) on Android, Windows and Linux

A .jar file can be very different things depending on where it came from: a Minecraft mod, a desktop program written in Java, an old phone game from before smartphones, or a piece of a software project. People who search how to open one usually want one of two things: to run it, or to see what’s inside.

A JAR is a ZIP archive of Java code. Folders opens it like a folder on Android, Windows and Linux, for free, so you can look inside, read its text files and extract them. Running a JAR is a different job that needs Java; this guide covers both.

What is a .JAR file?

JAR stands for Java ARchive. It’s a ZIP file holding compiled Java classes (.class files), resources such as images, sounds and settings, and a folder called META-INF with a MANIFEST.MF text file that describes the archive. If the manifest names a Main-Class, the JAR is a runnable program: with Java installed, java -jar app.jar starts it.

Two relatives use the same ZIP-based idea:

Extension	What it is
.jar	Java archive: a library, a program, a Minecraft mod or an old Java phone game
.war	Web application archive: a Java web app for servers such as Tomcat or Jetty, with a WEB-INF folder
.aar	Android archive: a library for Android app developers, with classes.jar, AndroidManifest.xml and resources

Where you might have got one:

• Minecraft: Java Edition mods and server plugins are JAR files.
• Old phone games from the Java ME (J2ME) era were JARs, often with a .jad file beside them.
• Desktop programs written in Java are sometimes shared as a single runnable JAR.
• Developers meet WAR files when deploying web apps, and AAR files when adding libraries to an Android project. An AAR isn’t an app and can’t be installed on a phone.

How to open a .JAR file with Folders

1. Install Folders from the download page and allow file access.
2. Find the JAR, WAR or AAR, or search for .jar.
3. Tap it. It opens like a folder, with the number of files and their unpacked size at the top.

On Android, from another app, choose Open with → Folders. On Windows, open it in Folders, or right-click it in File Explorer and choose Open with → Folders (if Java is installed, a double-click usually runs the JAR instead). On Linux, double-click it in Folders.

What you can do with it in Folders

• Read the manifest. Tap META-INF/MANIFEST.MF to read the version, the main class and other details as text.
• Open text and pictures inside. Settings files, JSON, licences and icons open directly in Folders’ text editor or image viewer. So do XML files such as a WAR’s WEB-INF/web.xml and an AAR’s AndroidManifest.xml, which in an AAR is still plain text, unlike in an installed app.
• Search in archive to find a class or a settings file by name, and Sort the list.
• Archive info for details of the archive itself.
• Extract all, or select files and Extract selected, with progress and a cancel button.

Folders doesn’t run JARs and doesn’t decompile code. A .class file is compiled bytecode, not readable source: Folders shows its raw bytes in the hex viewer, but reading it as Java needs a decompiler. And since Folders creates only ZIP files, it can’t repack a changed JAR.

Other ways to open .JAR files

• Java, for example the free Eclipse Temurin builds, to run a JAR on Windows or Linux: double-click it, or run java -jar file.jar.
• 7-Zip or any other ZIP tool, to look inside, since a JAR is a ZIP.
• JD-GUI or another Java decompiler, to read the code in .class files.
• J2ME Loader (free, Android), to play old Java phone games.

Problems opening a .JAR file?

Double-clicking does nothing on Windows. Java isn’t installed, or another program has taken over .jar files. Install a Java runtime, then right-click the JAR and choose Java under Open with.

Android won’t run the JAR. Android apps aren’t desktop Java programs, so a JAR doesn’t run on a phone. Old J2ME games run in an emulator such as J2ME Loader. Minecraft mods need Minecraft: Java Edition on a computer; the phone version (Bedrock) uses different add-on files.

“Invalid or corrupt jarfile”. The download is incomplete, or a web page was saved under the .jar name by mistake. If Folders can’t open it as an archive either, download it again.

It’s an AAR and you wanted an app. AAR files are building blocks for developers. To install an app you need an APK, or an XAPK or APKS bundle (XAPK guide).

Questions people ask

Can I open a JAR file on Android? Yes, to look inside and extract files: Folders opens it like a folder. Running it is another matter, as explained above.

Is a .jar file safe? Looking inside is safe, as Folders doesn’t run anything. Running a JAR gives it the same access to your computer as any program, and malware has been hidden in Minecraft mods before, so only run JARs from sources you trust.

How do I extract a JAR file? Open it in Folders and choose Extract all, or select the files you want and choose Extract selected.

JAR vs ZIP: what’s the difference? A JAR is a ZIP with a set layout (the META-INF folder and its manifest) that Java understands. Any ZIP tool can open one.

Related guides: ZIP, RAR and 7z files and Java and Kotlin source files. See all 382 file types Folders opens.