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JAR (Java Archive) file format

.jar  ·  package (ZIP variant)  ·  introduced 1996 by Sun Microsystems

What is a JAR (Java Archive) file?

A JAR is a Java Archive: a ZIP file containing compiled .class files plus a META-INF/MANIFEST.MF describing the entry point, classpath, and digital signatures. Variants include WAR (web application) and EAR (enterprise archive) for Java EE deployments.

Most readers reach this page after double-clicking a .jar file and finding their operating system unsure what to do with it. The good news: JAR (Java Archive) is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.

How to extract a JAR (Java Archive) file

Opening a .jar file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

  1. Locate the .jar file in File Explorer.
  2. Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
  3. If prompted, pick a destination folder and click Extract.
  4. The extracted files appear in a folder next to the original archive.

On macOS

  1. Find the .jar file in Finder.
  2. Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
  3. Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
  4. The extracted folder appears next to the archive.

On Linux

  1. Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).
  2. On the command line, run one of: 
    7z x archive.jar    # works for almost any format
  3. The files appear in the current directory.

How to create a JAR (Java Archive) file

To pack files into a .jar archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write JAR (Java Archive).

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .jar files.

If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.

Strengths

  • Cross-platform Java standard
  • Standard ZIP underneath
  • Code signing built in

Weaknesses and limitations

  • JVM required
  • Same compression limitations as ZIP

Typical use cases

  • Java application distribution
  • Library packaging (Maven, Gradle)
  • Web application deployment (WAR)

Technical details

JAR (Java Archive) uses the ZIP + META-INF/MANIFEST.MF algorithm and is identified on disk by the magic byte sequence 50 4B 03 04. The standard MIME type is application/java-archive. The format is an open specification and is free for any use.

Frequently asked questions

Is JAR (Java Archive) safe to open?

Archive files are containers — they are only as safe as what they contain. A .jar from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.

What is the maximum file size?

Modern ZIP-based formats use the ZIP64 extension to support archives larger than 4 GB and individual files larger than 4 GB, up to 16 EB in theory. Older tooling that does not understand ZIP64 will report a corruption error on such files.

Can I password-protect a JAR (Java Archive)?

Some archivers can wrap JAR (Java Archive) files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does JAR (Java Archive) compare to other formats?

See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.

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