Using the right Java

The right Java version to use is Java 8, with the same architecture as your CPU. If you don't know how to get it, read on.

Linux

The situation here can vary, depending on distribution. What you most likely want is openjdk 8.

Common issue is that people install only the headless version, and then it doesn't work. Make sure you have the full desktop version. Headless is for servers.

Unbuntu/Debian derivatives

# apt-get install openjdk-8-jre

Arch

# pacman -Sy jre8-openjdk

RPM-based distributions

# yum install java-1.8.0-openjdk

Windows

• Go to https://www.java.com/en/download/manual.jsp
• Download the Windows Offline (64-bit) installer, if your CPU is 64bit.
• Download the Windows Offline installer, if your CPU is 32bit - you will be limited to roughly 1500MB Java heap size, which is not big enough for mods in most cases.
• Install it.
• In MultiMC, set it up using the Auto detect feature in the main settings - see Java-settings for details.
• See Increasing Java's memory allocation for more details about Java memory settings.

There is an exception when using some poorly supported/unsupported old integrated GPUs from Intel. See Unsupported-Intel-GPUs for details.

macOS