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    Compress a JAR archive

    Compress JAR (Java Archive) files, a specialized ZIP format containing compiled Java bytecode and its resources.

    Accepted source formats

    JAR

    How it works

    1

    Drop your JAR.

    2

    The tool re-analyzes the content and applies maximum ZIP compression.

    3

    Download the compressed JAR, still executable and JVM-compatible.

    Common mistakes

    • Using a source file of poor quality.
    • Publishing without checking the final result.
    • Confusing file size, dimensions and quality.
    • Overwriting the original file without keeping a copy.

    Pro tips

    • Always keep an original version.
    • Test several settings before downloading.
    • Use WebP for the web when possible.
    • Choose descriptive file names for SEO.

    Privacy and file handling

    File handling depends on the selected tool and format. For sensitive files, review the tool information before starting the operation.

    How to convert a JAR file to Compress a JAR archive?

    Drag and drop or select your JAR file from your device. Click "Convert" and wait a few seconds. Get your converted Compress a JAR archive file instantly. Always check the output file before sharing it. If a file fails, try a smaller version or split it when the tool supports that workflow.

    Supported formats

    Source format: JAR. Target format: Compress a JAR archive. The final format should match how you plan to use it. Choose a file, run the conversion, then check the result before downloading it. The practical file-size limit depends on the format, browser and memory available on your device.

    What is the maximum JAR file size?

    The practical file-size limit depends on the format, browser and memory available on your device. If a file fails, try a smaller version or split it when the tool supports that workflow. Some elements may change during conversion, so open the output and check it before using or sharing it.

    Which browsers are compatible?

    Use a recent, up-to-date browser. Behaviour can vary with the file format, available memory and the features supported by your device. Always check the output file before sharing it. The final format should match how you plan to use it. Keep the original until you have approved the result.

    Can I use the tool on mobile?

    You can try the tool on a phone or tablet with a recent browser. Large files may require more memory or be easier to process on a desktop computer. Choose a file, run the conversion, then check the result before downloading it. Current quotas and higher plans are shown on the Pricing page.

    Discover all our tools

    Convert, compress, merge and edit your files in a few clicks.

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    Guides and tutorials

    Learn how to use our tools with our detailed guides.

    Frequently asked questions

    Yes, a JAR is technically a structured ZIP. Re-compressing with a more efficient algorithm (max Deflate or ZStd) doesn't alter any byte of the Java bytecode — the file stays 100% executable.

    Yes, `java -jar my-file.jar` works identically. The JVM decompresses content on the fly with no additional configuration.

    10-30% typically on a standard JAR (already-compact bytecode). On a JAR containing many resources (images, sounds, text), gain can reach 50-70% by pruning embedded resources.

    Yes, a JAR reads with any ZIP tool (7-Zip, WinRAR, tar). Our tool shows you the file list before compression so you can remove unused ones.

    Yes, our compression keeps the META-INF structure needed by Bukkit/Fabric/Forge. The compressed mod stays loadable by the server or Minecraft client.
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