Java and MegaMek

Last updated: May 2026

TL;DR

• 0.50.x (current Milestone) → requires Java 17 (LTS) or newer
• 0.51.0 and later → requires Java 21 (LTS)
• Recommended: Install Java 21 LTS via Adoptium Temurin

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A Note on Adoptium Temurin

Adoptium Temurin is Java. It's the free, open-source build maintained by the Eclipse Foundation — the same OpenJDK source as Oracle's, just packaged without the commercial license attached.

When this wiki says "install Java," we mean Temurin.

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Java Version Compatibility

MegaMek Version	Required Java	Java Released	Adoptium Support Through
0.50.x (current Milestone)	Java 17 (LTS) or newer	Sep 2021	At least Oct 2027
0.51.0+ (next major)	Java 21 (LTS)	Sep 2023	At least Oct 2029

Java 25

Java 25 LTS was released September 2025. We are currently testing it but it is not officially supported yet. Stick with Java 21 LTS for now.

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32-bit Windows Users

32-bit Windows can only run Java 17 — Java 21 dropped 32-bit support entirely.

This means 32-bit Windows users will be limited to the 0.50.x line once 0.51.0 ships. If you have the option to move to 64-bit Windows, this is a good time to plan that upgrade.

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Checking Your Installed Java Version

Not sure what's installed? See How to Check the Installed Java Version.

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How to Install Java

The current step-by-step installation guide (Windows + Mac, with screenshots) lives on the main MegaMek website:

→ megamek.org Installation Guide

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Legacy Version Information

The following Java versions are no longer supported by any current MegaMek release. They are retained here for historical reference only. If you are running any of these older MegaMek versions, please update to the current Milestone release.

MegaMek Version	Java	Status
0.49.11 to 0.49.x	Java 17 (LTS)	No longer maintained
0.49.0 to 0.49.10	Java 11 (LTS)	No longer maintained
0.48.0-Stable	Java 8 (LTS)	No longer maintained