Aikar's Flags for Minecraft Servers

Add Aikar’s JVM flags to your Minecraft server to reduce lag spikes and prevent out-of-memory (OOM) crashes. These flags optimize how Java manages your server’s memory.

Add Aikar’s Flags

1. In the Game Panel, go to Configuration > Server Options
2. Find the JVM Flags field
3. Copy the flags below and paste them into the JVM Flags field:

-XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -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 -Dusing.aikars.flags=https://mcflags.emc.gs -Daikars.new.flags=true

4. Click Save
5. Click Restart to apply the changes

Your startup command updates automatically. You should notice fewer lag spikes and more stable memory usage after the restart.

What Aikar’s Flags Do

Your Minecraft server shares its RAM with Java itself. Java needs some of that RAM for a background task called garbage collection (GC), which clears out data the server no longer needs.

Without Aikar’s Flags, the server can use up so much RAM that Java runs out of room to do garbage collection. This causes lag spikes when GC runs, or an out-of-memory (OOM) crash when it can’t run at all.

Aikar’s Flags fix this by telling Java how to split RAM between the server and GC. They set aside enough memory for GC to run smoothly, so your server stays stable.

Why Overhead Matters

“Overhead” is the RAM reserved for Java’s internal tasks (garbage collection, class loading, and other background work). It is not available to the Minecraft server itself.

WinterNode reserves approximately 1.5 GB of overhead on plans that need it. Aikar’s Flags help Java use that overhead efficiently, so your server gets the most out of its remaining RAM.

Further Reading

For a full technical breakdown, see the Aikar’s Flags documentation on Paper Docs.