Background

Installing Java

Java is required in order to run Minecraft. As such, until Java downloading is implemented, you will need to manually install Java to run Minecraft with PolyMC.

Currently, we recommend heading over to Adoptium to install the latest versions of Java. Minecraft 1.17 and upwards will require Temurin 17 (LTS), while anything below will require Temurin 8 (LTS).

  • 1.17 or newer: Temurin 17 (LTS)
  • 1.16.5 or older: Temurin 8 (LTS)

If you aren't sure which version you will need, it is recommended to just install both.

NOTE: You can use any OpenJDK build you want. Azul Zulu is a popular alternative to Temurin, and will work just as well.

You can also use Oracle Java, but openjdk is better here. Also to download Oracle Java 9+ you need an Oracle account which is not a good thing.

Java on linux

On Linux, it's recommended to use your package manager for installing Java.

Fedora

On the COPR package all required java versions should be installed, but this is the command to install it:

sudo dnf install java-1.8.0-openjdk java-17-openjdk

Void Linux 

sudo xbps-install openjdk17-jre openjdk8-jre

Arch Linux 

sudo pacman -S jre17-openjdk jre8-openjdk

Ubuntu 

sudo apt install openjdk-17-jre openjdk-8-jre

Debian 

sudo apt install openjdk-17-jre

Java 8 is not available from Debian repos for unknown reasons, but you can get a deb from Azul

Flatpak

The PolyMC flatpak already bundles java.

NixOS

The PolyMC NixOS package already bundles java.

Special cases

Forge 1.16.5 and Java 8u321+

Old versions of Forge crash with Java 8u321+. For this reason, using Java 8u312 or lower is reccomended

Using Java

Once you have installed Java, PolyMC will be able to detect it during the first time set-up wizard.

If you installed Java after already completing the first time setup process, you can access and modify your Java configuration through:

Settings > Java > Java Runtime > Auto-detect...

A note about Intel HD 2000/3000 on Windows 10

Since those igpus are not officially supported on Windows 10, with them the game is likely going to crash with any modern java binary.

For 1.16.5 or older there's a workaround, you need to install an older java binary (note: these links are official MultiMC links, and we can't guarantee the safety of the content on them):

After you download the required java binary for your architecture, extract the zip, and move the folder to your PolyMC data folder (%appdata%/PolyMC for notportable, the PolyMC folder for portable builds), you need to go to the PolyMC java settings, then to browse, then go to the folder with this particular java, click java.exe then open.
This should fix your issue.
Unfortunately there's no workaround for java 17 (and so newer Minecraft), so you can only downgrade your Windows or switch to Linux there.
If you want to try, there's this guide that could work. Nothing is guaranteed here, though.

Older Minecraft on MacOS

If you use some older Minecraft versions, you might have had this error:

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'NSWindow drag regions should only be invalidated on the Main Thread!'

Well, for you there's a resolution too!

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