Prism Launcher Java & JVM Configuration
Match the exact Java runtime (Java 21, Java 17, or Java 8) to your Minecraft version, tune min/max RAM, and pass GC JVM arguments.
Prism Launcher could not reserve enough space for object heap
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Fix "could not reserve enough space for object heap" in Prism Launcher: Java runtime, memory slider, and instance log.
- Issue
- could not reserve enough space for object heap
- First check
- Edit Instance → Settings → Java
could not reserve enough space for object heap
"prism launcher could not reserve enough space for object heap" is a common support search. Read the instance log before reinstalling the pack.
Match Java to the Minecraft version (8 / 17 / 21). Do not give a 1.16 pack Java 21 unless the pack says so.
Installer: /download.
Frequently asked questions
Auto-download Java?
Prism can fetch a matching runtime. Point the instance at that install.
Get Prism Launcher
Windows, macOS & Linux
Free and open source. Sign in with the Microsoft account that owns Minecraft, then create your first instance.
