Installing and Migrating

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


 * For compatible mods, please see Additional Mods,
 * For backups, please see Backups and Recovery,
 * For server installation and updates, please see Server Setup.

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

MultiMC or Prism Launcher with Java 9-19
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 11, make sure you are not installing it in a OneDrive folder!
 * 2) Download a MMC/Prism Java9-19 version of the pack from http://downloads.gtnewhorizons.com/Multi_mc_downloads/ (it might just be labelled Java9, that is still correct; currently (12. Mar 23) the Version labelled "...(MultiMC)..." is the java 8 Version, the version labelled "...(PrismLauncher)..." is the java 17-19 version. 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 19. 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 Adaptium.
 * 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 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 9+ version of GTNH with Java 17 or Java 19, you should not need any extra Java arguments.

=Upgrading=

Technic
The releases are pushed to Technic at a slower rate, once they have completed testing. Sometimes a release can be pushed to Technic for testing. To see them, please refer to the Technic configuration window.

ATLauncher

 * 1) Backup your GTNH instance. In ATLauncher, click on the Edit Instance drop-down and select Clone Instance. Click the Open Folder button for the new instance.
 * 2) Delete the,  ,   and   (only in old versions) folders from.
 * 3) 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.
 * 4) Port over any customized config settings. Use your backup as a reference.
 * 5) The questbook should be updated automatically. If it was not updated, you can either use the default load block, go to cheat mode and do  to load quest book changes, or do   on a server.

MultiMC

 * 1) Backup your GTNH instance. In MultiMC, Right Click on the instance and select Copy Instance. With the backup, you retain access to settings and configs that are later needed on the new version, also to screenshots and keybinds.
 * 2) Delete the,  ,   and   (only in old versions) folders from.
 * 3) 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.
 * 4) Port over any customized config settings. Use your backup as a reference.
 * 5) The questbook should be updated automatically. If it was not updated, you can either use the default load block, go to cheat mode and do  to load quest book changes, or do   on a server.

Upgrading from Java 8 to Java 9-19
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.

=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