Why performance matters
Your Minecraft launcher's performance directly affects your players' experience. A slow launcher, endless loading times, or in-game FPS drops lead to frustration and churn. As a server admin, your reputation is on the line.
Player experience: a player who waits 10 minutes to launch the game probably won't come back. Launcher performance shapes the first impression and long-term retention.
Server reputation: players associate the quality of your launcher with the quality of your server. An optimized launcher sends a professional, reassuring signal.
Choosing the right Java version
The choice of Java version has a significant impact on Minecraft's performance. In 2026, two versions coexist, and the right choice depends on your Minecraft version and your mods.
Java 17
The required version for Minecraft 1.18 and above. It's the current standard for most servers. Stable, widely supported by mods and mod loaders.
Java 21
The latest LTS release. Offers garbage collector improvements and overall performance gains. Recommended for Minecraft 1.21+ if your mods support it. Check compatibility before migrating.
CraftLauncher lets you choose the Java version in the launcher settings, and installs it automatically for your players. No more asking everyone to configure Java by hand.
Optimizing JVM arguments
The JVM arguments passed when Minecraft launches determine how the virtual machine manages memory and the CPU. Misconfigured arguments are the number one cause of FPS drops and freezes.
Essential arguments
-Xms4G -Xmx4G
Sets the minimum (Xms) and maximum (Xmx) memory allocated to Java. Recommendation: 4 GB for a light modpack, 6-8 GB for a heavy one. Never exceed half of your system's total RAM.
-XX:+UseG1GC
Enables the G1 garbage collector, optimized for memory-hungry applications like Minecraft. It reduces micro-freezes caused by garbage collection.
Aikar's Flags
Aikar's flags are a set of JVM arguments specifically tuned for Minecraft. They fine-tune G1GC to minimize garbage collection pauses. This is the reference the community recommends in 2026.
-XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem -XX:MaxTenuringThreshold=1
CraftLauncher automatically applies the best JVM arguments based on the amount of RAM and the type of modpack configured. Your players don't have to change anything.
Picking the right performance mods
Some mods are specifically designed to improve Minecraft's performance. Including them in your launcher can multiply FPS by 2 or 3 depending on the setup.
Sodium
Replaces Minecraft's rendering engine. Improves FPS by 200% to 500% depending on the case. Fabric only. Forge alternative: Rubidium.
Lithium
Optimizes server-side logic: entity AI, physics, chunk loading. Improves TPS (ticks per second) without changing gameplay. Fabric compatible.
Starlight
Rewrites Minecraft's lighting engine. Drastically cuts chunk generation time and eliminates light-related lag. Note: built into Minecraft 1.20+ natively.
FerriteCore
Reduces Minecraft's memory usage by optimizing internal data structures. Especially useful for heavy modpacks exceeding 4 GB of RAM.
ModernFix
Fixes numerous performance issues in modded Minecraft. Reduces load time, memory usage, and freezes. Compatible with Forge and Fabric.
Cutting down on unnecessary mods
Every mod adds to load time and memory usage. A modpack with 200 mods will always be slower than one with 50, even with the best optimizations.
Auditing your mods
Go through every mod in your modpack and ask yourself: is this actually used by my players? Unused decoration mods, debug mods, or mods with overlapping features are obvious candidates for removal.
Client-side vs Server-side
Understanding the difference between client and server mods is essential. Performance mods like Sodium, Lithium, and FerriteCore are client-side: they don't need to be installed on the server. Content mods (new blocks, dimensions, mechanics) are often server-side and must be present on both.
- Client-side: shaders, minimaps, HUD, performance, animations
- Server-side: content mods, protection, economy, worldgen
- Both: content mods with graphical components (Create, Botania)