Match Java to Minecraft

The runtime must match the game#

Java is the runtime that executes a Minecraft server. A Java release can be too old for a newer server, while some old mod loaders or mods do not support the newest Java. Crafty’s container may include several Java versions; choose the one required by the exact Minecraft release.

For vanilla and Fabric, use this starting point. Individual modpacks and server implementations can require a different runtime.

Using Paper? Follow Paper's own requirements ↗: its recommended runtime is Java 21 for Minecraft 1.20 through 1.21.11, and Java 25 for 26.1 and later. Do not use the vanilla/Fabric table to override your chosen server's instructions.

Recognize a Java error#

“Unsupported class file major version,” “compiled by a more recent version,” or a message requesting a specific Java release usually means the selected runtime is too old. Immediate crashes involving removed Java modules can mean it is too new for an old pack.

1. 1
   Stop the server cleanly and record the exact Minecraft, server-software or modpack release.
2. 2
   Check the launch method used by your saved plan:

• Crafty: open the server’s Config/runtime selection and choose the matching bundled Java.
• Windows start script: run java -version, install the required runtime, and make sure start.bat launches that executable.
• Linux service or terminal: run java -version as the server user and check the Java path in the systemd service or launch command.
• Hosting panel: choose a supported Java image/runtime for this exact server release; ask the provider if the required version is absent.

1. 1
   Select or install the Java release required by the exact Minecraft release or server-pack documentation.
2. 2
   Start the server and read the first specific error—not only the final “process exited” line.
3. 3
   Keep an older runtime if another server still depends on it; change one server’s launch path rather than replacing Java blindly.