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Requirements

RequirementVersionNotes
Java21Oracle JDK 21 recommended
Minecraft1.21.1Exact version required
NeoForge21.1.xTested against 21.1.209
JEI19.25.0.322 (1.21.1)Optional, strongly recommended
General Mechanics targets Minecraft 1.21.1 with NeoForge 21.1.x exactly. Using a different NeoForge major version or a different Minecraft version will prevent the mod from loading.

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Player installation (client)

1

Install Java 21

Minecraft 1.21.1 bundles Java 21. If you launch through the official Minecraft launcher, no separate Java installation is needed. For manual setups, install Oracle JDK 21.
2

Install NeoForge

Download the NeoForge installer for version 21.1.x and run it:
java -jar neoforge-21.1.209-installer.jar
Select Install client and point the installer at your Minecraft directory. The installer creates a NeoForge launch profile in the Minecraft launcher.
3

Download General Mechanics

Download gm-1.0.0.jar from the mod’s distribution page.
4

Place the JAR in the mods folder

Copy the JAR into your mods folder.
Windows:  %APPDATA%\.minecraft\mods\
macOS:    ~/Library/Application Support/minecraft/mods/
Linux:    ~/.minecraft/mods/
Create the mods folder if it does not exist.
5

(Optional) Install JEI

Download the JEI JAR for NeoForge 1.21.1 (version 19.25.0.322) and place it in the same mods folder.
6

Launch and verify

Open the Minecraft launcher, select the NeoForge 1.21.1 profile, and click Play. From the main menu, open Mods and confirm General Mechanics (gm) appears in the list at version 1.0.0.

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Server installation (dedicated server)

1

Install Java 21 on the server

Install Oracle JDK 21 on the server machine.
java -version
# Should report: java version "21"
2

Install NeoForge server

Run the NeoForge installer with the server option:
java -jar neoforge-21.1.209-installer.jar --installServer /path/to/server
3

Place the mod JAR

Copy gm-1.0.0.jar into the server’s mods folder:
/path/to/server/mods/gm-1.0.0.jar
4

(Optional) Install JEI on the server

JEI is a client-side mod but can be present on the server. Place the JEI JAR in the server’s mods folder if you want server-side recipe integration.
5

Start the server

Start the server with the --nogui flag to run without a graphical interface:
java -jar server.jar --nogui
The --nogui flag is the standard way to run a NeoForge dedicated server in a headless environment. Without it, the server attempts to open a Swing GUI window.
6

Verify

Check the server log for a line confirming gm loaded successfully. You should see output from the General Mechanics logger during startup.

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Optional dependencies

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JEI (Just Enough Items)

JEI is not required but is strongly recommended. It provides in-game recipe browsing for all General Mechanics machines and processes.
  • Version: 19.25.0.322 for Minecraft 1.21.1 NeoForge
  • Without JEI, recipes are still functional but not browsable in-game.

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Verification

After installation, confirm the mod is active:
  1. In-game: open Mods from the main menu and locate General Mechanics (gm, version 1.0.0).
  2. In a world: open your inventory and check for General Mechanics creative tabs.

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Troubleshooting

  • Confirm the JAR is in the correct mods folder for the NeoForge profile you are launching.
  • Confirm you selected the NeoForge 1.21.1 profile in the launcher, not the vanilla profile.
  • Check the crash report or latest.log in the logs folder for load errors.
General Mechanics targets NeoForge 21.1.x. If you have a different major version installed (for example 21.0.x or 21.2.x), the mod will fail to load.Uninstall the current NeoForge version and install 21.1.209 or another 21.1.x release.
If you see an UnsupportedClassVersionError or similar error on startup, the JVM running Minecraft is older than Java 21.
  • For the official launcher: ensure you are using a recent Minecraft launcher that bundles Java 21.
  • For manual setups: install Oracle JDK 21 and point your launch script at it.
# Verify the Java version in use
java -version
# Expected output includes: java version "21"
  • Confirm --nogui is present in your startup command if running headless.
  • Check logs/latest.log for the root cause. NeoForge logs mod loading errors with full stack traces.
  • Verify all required mods (NeoForge itself) are correctly installed and no optional mods have version conflicts.

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