What Happens When You Open a JAR File?

A walkthrough of what's inside a JAR file — ZIP structure, MANIFEST.MF, class files, resources, META-INF signatures — and what different tools do when you open one.

Step 1: The ZIP Unwrap

Step 2: The Entry Listing

Step 3: The Manifest Read

Step 4: Signature Verification (If Present)

Step 5: Class File Parsing

Step 6: Resource Access

What Different Tools Do When They "Open" a JAR

Common Questions When Opening a JAR