Installing and Migrating

This page shows how to install, update, or migrate a GTNH client.


 * For compatible mods, see Additional Mods,
 * For texture packs, see Resource Packs,
 * For backups, see Backups and Recovery (already included for singleplayer),
 * For server installation and updates, see Server Setup.
 * For nightly testing builds, see Nightly builds.

Installing
For all launchers, 5-7 GB of memory (RAM) is recommended for GTNH in singleplayer.

Generally, it is recommended to install the latest stable release -- the version that ends on ".0".

If you want to play on a server, then your GTNH client needs to be of the same version as the server.

If you want to play on a more up-to-date dev release for testing or to get the latest features, you can check Dev Release Stability to see if they have serious problems.

MultiMC or Prism Launcher with Java 17-20
At the moment, newer Java versions can only be used with MultiMC or Prism Launcher. If you are experiencing issues with fullscreen mode, set a resolution in your launcher and check other settings in the config/lwjgl3ify.cfg config file.
 * 1) Install MultiMC or Prism Launcher. If you are on Windows 10 or 11, make sure you are not installing it in a OneDrive folder!
 * 2) Download a MMC/Prism Java17-20 version of the pack from http://downloads.gtnewhorizons.com/Multi_mc_downloads/ (they are currently labelled as java17-19 or java17-20). Drag it into the MultiMC/Prism window to create the instance.
 * 3) Under settings - Java, make sure you are using a new version of Java, best 64-bit Java 17 or 64-bit Java 20. In the case of Java 17 make sure you are updated to at least 17.0.6, older variants can cause start-up errors. Java 17 can be downloaded from Adoptium.
 * 4) If you are using MultiMC you also need to add the additional Java arguments from here. You only want the Java args from that page, nothing else. This step is not needed in Prism.

MultiMC with Java 8

 * 1) Install MultiMC. If you are on Windows 10 or 11, make sure you are not installing it in a OneDrive folder!
 * 2) Download a MMC version of the pack from http://downloads.gtnewhorizons.com/Multi_mc_downloads/ and drag it into the MultiMC window to create the instance.
 * 3) Under settings - Java, make sure you are using a version of 64-bit Java 8.

Technic

 * 1) Install the Technic launcher,
 * 2) In the launcher, go to the Modpacks tab and enter "GT New Horizons" in the search box. Make sure the pack named "GT New Horizons" is selected in the results list.
 * 3) Optionally, click the Modpack settings link in the upper-right to select a specific version and the installation path. By default, the latest stable release will be installed, but some servers may need a different version.
 * 4) Click the Install button on the lower right to install the pack.
 * 5) Go to the Launcher settings at the top-right corner, and the Java tab of that dialog. Make sure you are using an up to date, 64-bit Java 8.

Curseforge Launcher
The Curseforge launcher is not recommended because:
 * it usually is out-of-date,
 * it constantly messes up recipes,
 * its new license requirements on mods make things even worse.

Please do not use a Curseforge launcher for GTNH.

Java Arguments
GTNH runs best with configured Java arguments for targeted garbage collection and memory usage. Optimal arguments will vary depending on hardware, launcher and build version.


 * A History of Modded Minecraft Memory Usage
 * Modded Minecraft Performace Benchmarks
 * Low End PCs

Note that these instructions are for the normal Java 8 version of GTNH. If you are playing on a Java 17-20 version of GTNH with Java 17 or Java 20, you should not need any extra Java arguments.

The usual process

 * 1) Backup your GTNH instance to port settings and configs later. It is done by cloning the instance in the launcher.
 * 2) In ATLauncher, select Edit Instance > Clone Instance in the drop-down. Select the Open Folder button for a new instance.
 * 3) In MultiMC, select Copy Instance in the drop-down.
 * 4) Delete the folders  and   from  . Also delete the folders   and   if you have them. They don't even exist on newer versions though.
 * 5) Replace the deleted folders with the ones from the downloaded archive. They are contained in a .minecraft folder after unpacking. If you are on Mac or Linux, you may have to show hidden files for your OS.
 * 6) Port over any customized config settings. Use your backup as a reference.
 * 7) Update your questbook. You can do that either by using the default load block, or by running the command  in the chat when you're in the game. For that, you will need to go into cheat mode if in single player or to have "op" privileges on the server. The loading process usually takes less than a minute. You should see a chat message once it's finished.

Upgrading from Java 8 to Java 17-20
The easiest option is to follow the instruction under installing above to set up a new instance. Keep your old instance as a backup for a while. Follow the migrating section below to copy your existing world to the new instance.

Alternatively, you can follow the full instructions here on https://github.com/GTNewHorizons/lwjgl3ify#client.

Migrating to a different installer
This part describes how to migrate the installation to a new launcher. It is highly recommended to keep your old launcher and files around for a while as a backup.

Files to copy over

 * 1) If playing in single-player, copy over your folder.
 * 2) The  folder - if you use a different map/waypoint tool find its data.
 * 3) The  folder.
 * 4) The folder
 * 5) Any custom resources/resourcepacks you are using.
 * 6)  (also   if you use optifine).
 * 7) Your  folder, if you want to keep them
 * 8) Any custom (client-side or not) mods such as InGameInfoXML and its configuration file.
 * 9) Your backups in the  folder (feel free to only grab 1 or 2 if you aren't deleting it)
 * 10) Any custom changes to the config files or script files
 * 11) Consider keeping the logs folder if you crash a lot