Question 1

What is a JAR file?

Accepted Answer

JAR (Java Archive) is a ZIP-based package format for Java class files and associated metadata. A JAR contains .class files (compiled Java bytecode), optional resources (images, properties files), and a META-INF/MANIFEST.MF file that declares metadata like the Main-Class, Class-Path, and Signature-Version.

Question 2

How does this tool work?

Accepted Answer

We parse the JAR as a ZIP archive using a pure-JavaScript parser (supports STORE and DEFLATE entries via DecompressionStream). We list every file inside, identify .class files, find and parse META-INF/MANIFEST.MF into a key-value attribute map, detect the Main-Class attribute (entry point), and let you extract individual files or re-zip everything as a standard ZIP.

Question 3

Can I run the JAR?

Accepted Answer

No. Running JARs requires a Java Runtime Environment (JRE) and `java -jar` command, neither of which runs in a browser. This tool is for inspecting JAR contents — useful for security research, verifying dependencies, extracting resources, or understanding what's inside before deploying.

Question 4

Can I decompile the .class files?

Accepted Answer

No — we list and extract .class files but do not decompile them. Decompiling Java bytecode to readable source requires tools like CFR, Procyon, or JD-GUI, which run as desktop apps. You can extract .class files here and run them through a decompiler offline.

Question 5

What's in the manifest viewer?

Accepted Answer

The META-INF/MANIFEST.MF file is a plain-text file with `Key: Value` pairs separated by colons, with line continuations (lines starting with a space continue the previous value). We parse it into an interactive key-value viewer that shows every attribute, including Manifest-Version, Created-By, Main-Class, Class-Path, and any custom attributes. Signature-related entries (CERT.SF, CERT.RSA) are listed but not parsed.

Question 6

What extra features does this tool have compared to others?

Accepted Answer

10 extras: (1) Drag-drop input. (2) File tree grouped by package path. (3) Search files by name (class name, resource name). (4) Filter by file type (.class, .properties, .xml, images, signatures). (5) Stats — file count, class file count, total uncompressed size, compression ratio. (6) Manifest viewer (parsed key-value pairs). (7) Main-Class detector with prominent display. (8) Download individual files. (9) Download all as ZIP (re-zip STORE method). (10) History of recently inspected JARs (localStorage — last 10).

Question 7

Is my JAR uploaded anywhere?

Accepted Answer

No. All JAR parsing runs in your browser using pure JavaScript. File contents never leave your device. Only archive summaries (filename + main class + entry count) are saved to local history for convenience.

Question 8

Can I see what libraries a JAR depends on?

Accepted Answer

Yes — if the manifest declares a `Class-Path` attribute, we display it in the manifest viewer. Note that this only shows libraries the JAR explicitly declares in its manifest — transitive dependencies (managed by Maven/Gradle) are not in the JAR file itself. For full dependency analysis, use `jdeps` (ships with the JDK).

JAR Extractor

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