What is a JAR file?
A JAR file is a Java archive format based on ZIP. It can include Java CLASS files, resources, images, configuration files, and a manifest file. Many Java libraries and Java applications are distributed as JAR files.
How to open a JAR file on Android
Install Jar File Opener from Google Play, open the app, choose your JAR file from device storage, and browse the archive contents. You can open supported text files, inspect CLASS files, and extract selected resources.
Common things to check
Start with META-INF/MANIFEST.MF. This file may include Main-Class, Created-By, Manifest-Version, and other metadata. If a JAR file cannot run, the Main-Class entry is often one of the first things to check.
Online vs Android app
The online tool is useful on desktop browsers for quick inspection. The Android app is better for mobile file access, offline use, and CLASS file decompilation features.
Use the homepage tool to inspect a JAR file locally in your browser, or download the Android app for offline file inspection on your phone.
Open Online Tool Download Android App