--- title: "Prism Launcher Java Guide — Java 21, Java 17, Java 8 & RAM Allocation | Prism Launcher for Windows" description: "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. Open-source Minecraft launcher for Windows 10 and 11. Download at /download." canonical: https://prismlauncher.ink/java updated: 2026-10-17 --- # 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. ## Facts (2026-10-17) - **Section:** Java - **Platform:** Windows 10 & Windows 11 (x64 / ARM64) - **Mod Platforms:** Modrinth, CurseForge, FTB, Technic, ATLauncher - **Installer:** Available at /download ## How Prism Launcher Java & JVM Configuration works on Windows 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. Using Adoptium Temurin or Prism's built-in Java auto-downloader on Windows to eliminate exit code 1 and lag spikes. Prism Launcher is a fast, lightweight C++/Qt launcher that keeps every Minecraft profile in its own isolated instance folder, with zero ads and no background bloatware. Get the Windows installer or portable ZIP from [/download](https://prismlauncher.ink/download), or dive into the guides linked below. ## Key advantages for modded Minecraft - **One-Click Mod Loaders:** Switch between [Fabric, NeoForge, Forge, and Quilt](https://prismlauncher.ink/loaders) inside any instance's Version tab. - **Built-in Mod & Modpack Browser:** Search and update [Modrinth and CurseForge modpacks](https://prismlauncher.ink/modpacks), shaders, and resource packs directly inside the app. - **Automatic Java Management:** Pair [Java 21, Java 17, and Java 8](https://prismlauncher.ink/java) per instance so modern 1.21 packs and classic 1.12.2 packs both launch cleanly. ## Pages in Prism Launcher Java & JVM Configuration - [Java 21 (64-Bit) for Minecraft 1.20.5 & 1.21+](https://prismlauncher.ink/java/java-21-temurin-minecraft-1-20-5-1-21) — Mojang upgraded Minecraft 1.20.5 and 1.21+ to require a 64-bit Java 21 runtime; launching with Java 17 or Java 8 causes an immediate incompatible class version crash. Applies to Minecraft 1.20.5, 1.20.6, 1.21 – 1.21.4+. - [Troubleshooting: Java 21 (64-Bit) for Minecraft 1.20.5 & 1.21+](https://prismlauncher.ink/java/java-21-temurin-minecraft-1-20-5-1-21-troubleshooting) — Step-by-step fix for Java version mismatches and JVM launch errors on Minecraft 1.20.5, 1.20.6, 1.21 – 1.21.4+. - [Java 17 (64-Bit) for Minecraft 1.18 – 1.20.4](https://prismlauncher.ink/java/java-17-temurin-minecraft-1-18-1-20-4) — The required LTS runtime for 1.18 through 1.20.4 Forge, Fabric, and Quilt modpacks. Applies to Minecraft 1.18, 1.19, 1.20.1 – 1.20.4. - [Troubleshooting: Java 17 (64-Bit) for Minecraft 1.18 – 1.20.4](https://prismlauncher.ink/java/java-17-temurin-minecraft-1-18-1-20-4-troubleshooting) — Step-by-step fix for Java version mismatches and JVM launch errors on Minecraft 1.18, 1.19, 1.20.1 – 1.20.4. - [Java 16 / Java 17 for Minecraft 1.17 – 1.17.1](https://prismlauncher.ink/java/java-16-minecraft-1-17-caves-and-cliffs) — Minecraft 1.17 originally targeted Java 16 and runs cleanly on 64-bit Java 17 LTS in Prism Launcher. Applies to Minecraft 1.17 – 1.17.1. - [Troubleshooting: Java 16 / Java 17 for Minecraft 1.17 – 1.17.1](https://prismlauncher.ink/java/java-16-minecraft-1-17-caves-and-cliffs-troubleshooting) — Step-by-step fix for Java version mismatches and JVM launch errors on Minecraft 1.17 – 1.17.1. - [Java 8 (64-Bit 1.8.0) for Minecraft 1.7.10, 1.12.2 & 1.16.5](https://prismlauncher.ink/java/java-8-64-bit-minecraft-1-7-10-1-12-2-1-16-5) — Older Forge versions on 1.7.10, 1.12.2, and 1.16.5 rely on Java 8 reflection internals and will crash with Exit Code 1 if launched on Java 17 or Java 21. Applies to Minecraft 1.1 – 1.16.5. - [Troubleshooting: Java 8 (64-Bit 1.8.0) for Minecraft 1.7.10, 1.12.2 & 1.16.5](https://prismlauncher.ink/java/java-8-64-bit-minecraft-1-7-10-1-12-2-1-16-5-troubleshooting) — Step-by-step fix for Java version mismatches and JVM launch errors on Minecraft 1.1 – 1.16.5. - [RAM Allocation (Minimum & Maximum Memory MiB)](https://prismlauncher.ink/java/ram-allocation-min-max-memory-slider) — Setting Maximum Memory too low causes OutOfMemory freezes, while setting it above 10–12 GB can cause long garbage-collection lag spikes. Applies to All Minecraft versions. - [Troubleshooting: RAM Allocation (Minimum & Maximum Memory MiB)](https://prismlauncher.ink/java/ram-allocation-min-max-memory-slider-troubleshooting) — Step-by-step fix for Java version mismatches and JVM launch errors on All Minecraft versions. - [JVM Arguments: Aikar's Flags, G1GC & Generational ZGC](https://prismlauncher.ink/java/aikars-flags-and-g1gc-zgc-jvm-arguments) — Custom garbage collection flags smooth out 1% low frame drops when generating chunks in 300-mod packs. Applies to Modded 1.12.2 – 1.21.4+. - [Troubleshooting: JVM Arguments: Aikar's Flags, G1GC & Generational ZGC](https://prismlauncher.ink/java/aikars-flags-and-g1gc-zgc-jvm-arguments-troubleshooting) — Step-by-step fix for Java version mismatches and JVM launch errors on Modded 1.12.2 – 1.21.4+. - [Complete Minecraft Java Version Chart (Java 8, Java 17 & Java 21)](https://prismlauncher.ink/java/which-java-version-for-each-minecraft-version) — Practical Windows guide for "which java version for minecraft prism launcher": instance setup, Java configuration, and mod management in Prism Launcher. - [How to Allocate More RAM to Minecraft in Prism Launcher](https://prismlauncher.ink/java/how-to-allocate-more-ram-in-prism-launcher) — Practical Windows guide for "how to allocate more ram in prism launcher": instance setup, Java configuration, and mod management in Prism Launcher. ## FAQ ### Where do I download Prism Launcher for Windows? Download the Windows installer or portable package directly from [/download](https://prismlauncher.ink/download) on this host. ### Does Prism Launcher work with both Modrinth and CurseForge? Yes. You can install complete modpacks or mix individual mods from both Modrinth and CurseForge inside the same instance. ## Related - [Java 21 (64-Bit) for Minecraft 1.20.5 & 1.21+](https://prismlauncher.ink/java/java-21-temurin-minecraft-1-20-5-1-21) - [Troubleshooting: Java 21 (64-Bit) for Minecraft 1.20.5 & 1.21+](https://prismlauncher.ink/java/java-21-temurin-minecraft-1-20-5-1-21-troubleshooting) - [Java 17 (64-Bit) for Minecraft 1.18 – 1.20.4](https://prismlauncher.ink/java/java-17-temurin-minecraft-1-18-1-20-4) - [Troubleshooting: Java 17 (64-Bit) for Minecraft 1.18 – 1.20.4](https://prismlauncher.ink/java/java-17-temurin-minecraft-1-18-1-20-4-troubleshooting) - [Java 16 / Java 17 for Minecraft 1.17 – 1.17.1](https://prismlauncher.ink/java/java-16-minecraft-1-17-caves-and-cliffs) ## Download Free and open source: [Download Prism Launcher](https://prismlauncher.ink/download) Markdown mirror: https://prismlauncher.ink/java.md