Minecraft 26.1 and newer need Java 25 on your server

Minecraft: Java Edition servers for version 26.1 and newer need Java 25. Older servers, from 1.20.5 up to 1.21.11, need Java 21. If you run a server yourself and update the game without updating Java, it won’t start. On Wilderack you don’t have to think about it: we pick the right Java for the version you choose.

What changed

Mojang moved Java Edition to year-based version numbers in 2026, starting with 26.1 in March. Every release since then, including 26.2 and the current 26.3, is built for Java 25. You can see it in Mojang’s own launcher data: each version lists the Java version it needs.

The Minecraft launcher downloads the right Java for players automatically, so this only matters for servers.

What happens with the wrong Java

A server started with Java that’s too old stops straight away with an error that mentions UnsupportedClassVersionError and a “class file version” number, such as “class file version 69.0” with “only recognizes class file versions up to 65.0”. Version 69 means the file needs Java 25, and 65 means the Java running it is 21.

On Wilderack

• The right Java is picked for you. When you choose a Minecraft version, or a modpack that needs one, your server runs it with the Java it needs. Switch back to an older version and it switches back too.
• Mods and plugins must match the version. Before you update, check that your mods or plugins support the new version. Our server types guide explains how Paper, Fabric and NeoForge handle updates.
• Back up before you update. We make a backup automatically before every version change, so you can go back if something doesn’t work.

Running your own server at home?

Install a Java 25 runtime (for example Eclipse Temurin 25) and make sure your start script uses it. Running java -version should print 25. If you keep older servers too, point each start script at the full path of the Java it needs.