Jarpeek
A free, browser-only tool that opens and decompiles Java JAR/WAR/CLASS files back into readable source code — nothing ever leaves your computer.
🔗 Visit Jarpeek
Description
If you've got a compiled Java program (a .jar file, a plugin, a mod) and want to see what it actually does without installing a desktop decompiler, Jarpeek does that entirely in your browser tab: drop in the file, and it turns the compiled bytecode back into readable Java source using the Vineflower decompiler, letting you browse the file tree, inspect classes, and search across the whole archive.
Because it runs client-side, the file you're inspecting never gets uploaded anywhere — a real advantage if you're looking at a plugin or mod you don't fully trust and don't want to send to a third-party server. It also goes a level deeper than just decompiling: you can inspect raw JVM bytecode instructions, constant pools, and class structures directly, and it can pull in Maven or Gradle dependencies straight from Maven Central for cross-reference. It supports English and Simplified Chinese and requires no installation or account.
💬 Our review
The short version: Jarpeek's client-side-only design is the feature that actually matters here — for a niche but real use case (inspecting a JAR you don't fully trust), not uploading the file anywhere is worth more than any convenience a desktop tool offers.
Compared to CFR or javap (the standard JDK tool), Jarpeek trades raw decompilation power for accessibility: CFR run locally can be more configurable for tricky bytecode, and javap gives you the officially blessed bytecode view, but neither works instantly from a browser tab with zero setup on a machine that isn't yours. The limits are what you'd expect from a browser tool: no API, no offline/desktop version if you need to work without internet, and support is email-only. Worth it if you need to quickly inspect a JAR/mod/plugin on any machine without installing anything, especially one you don't want to upload to a server; skip it if you're doing serious reverse-engineering work daily, where a local CFR or IDE-integrated decompiler will handle edge cases better.
💰 Pricing
📊 Global score
🤖 AI-enriched data
Entièrement gratuit, aucune inscription ni palier payant.
Pros
Traitement 100% côté client, le fichier ne quitte jamais l'appareil
Aucune installation ni inscription requise
Intégration Maven/Gradle pour inspecter les dépendances
Accessible depuis n'importe quel navigateur/machine
Cons
Aucun dépôt open-source
Dépendant du navigateur, pas de version hors-ligne
Aucune API pour un usage programmatique
Support par email uniquement