Practical, focused, step by step

Android File and Java Tutorials

Learn how to inspect JAR archives, run compatible Java apps, understand developer file formats and play Scratch SB3 projects on mobile devices.

Featured learning path

Understand a JAR file from the outside in

Begin by opening the archive, then inspect its manifest, extract what you need and analyze supported CLASS bytecode.

Jar File Opener overview →

01 · Start hereOpen JAR files on Android

Browse folders, identify entries and learn why opening is different from running.

02 · Read metadataView MANIFEST.MF

Understand Main-Class, Class-Path, versions and common formatting problems.

03 · Save resourcesExtract JAR files

Extract selected entries or a complete archive while avoiding overwrite issues.

04 · Analyze codeDecompile CLASS files

Compare source-like output, bytecode disassembly, metadata and raw hex.

Java on Android

Java runtime guides

Run compatible Java applications and understand the differences between JAR, CLASS, Swing and J2ME workflows.

Explore Jre4Android →

JAR executionHow to Run JAR Files on AndroidUse Jre4Android to run compatible Java JAR applications. Desktop UIRun Java Swing Apps on AndroidLaunch compatible Swing GUI apps with touch, zoom and virtual mouse controls. Compiled classesHow to Run .class Files on AndroidLaunch an individual compiled Java CLASS with the correct package and dependencies. Classic mobile JavaJ2ME Emulator for AndroidRun compatible Java ME applications and games on Android.

Developer files

Android file format guides

Inspect specialized files, recognize their structure and choose the correct viewer before extracting or executing anything.

View related apps →

Native libraryCheck Android 16KB Page Size SupportInspect ELF information and identify possible Android 16KB compatibility issues. Android expansion fileHow to Open OBB Files on AndroidBrowse and extract resources from Android OBB packages. Generic data fileHow to Open DAT Files on AndroidIdentify, view and extract supported DAT file content. Unknown fileIdentify a File by Its ContentsInspect file signatures, hashes, strings and metadata directly in your browser.

Scratch projects

SB3 project guides

Import and play Scratch-compatible .sb3 project files on iPhone, iPad and Android devices.

iPhone & iPadOpen Scratch SB3 Files on iOSImport and play an SB3 project on iOS or iPadOS. AndroidOpen Scratch SB3 Files on AndroidImport and play an SB3 project on an Android phone or tablet.