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Minecraft startup flags generator

Enter your RAM and get optimised Aikar's flags, scaled correctly (including the 12 GB+ tuning). Copy, paste into your start script, done.

Optimised startup command (Aikar's flags)

What are these flags?

They are the widely-used "Aikar's flags" — G1GC garbage-collector tuning that keeps a Minecraft server smooth and avoids lag spikes. Above 12 GB the heap-region and new-size values change, which this tool handles for you. Set -Xms and -Xmx to the same value (done here) so the JVM does not resize the heap.

New to running a server? See how to set up a Minecraft server, or skip the setup with managed Minecraft hosting (we apply flags like these by default).

FAQ

Straight answers.

What are Aikar's flags?

A well-known set of JVM/G1GC arguments that reduce lag and GC pauses on Minecraft servers. They're the community standard for Paper/Spigot/Forge.

Why set Xms equal to Xmx?

So the JVM allocates the full heap up front instead of growing it, which avoids stutter. This tool sets both to your chosen RAM.

Do bigger servers need different flags?

Yes — above ~12 GB, G1NewSizePercent, region size and a few others change. This generator switches automatically based on your RAM.

Do I need to do this on overnight.host?

No — our Minecraft hosting applies sensible flags by default. This tool is for anyone, including self-hosters.

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📚 Related guide
How to set up a Minecraft server →