Gaming

Minecraft Server Flag Generator

Generate optimized JVM startup flags for your Minecraft server. Pick a battle-tested preset — Aikar's, MeowIce, Benchmarked G1/ZGC/Shenandoah, Hilltty, Obydux, Etil — and ship a ready-to-run start.sh, .bat, .command, Dockerfile, systemd unit or Pterodactyl egg.

server types

flag presets

extras

output formats

Server softwarePick the engine running your server

Flag presetCurated, sourced flag bundles

Extra flag groups

Heap memory

4 GB

How much RAM should I allocate?

<10 players2-4 GB
10-30 players4-8 GB
30-60 players8-12 GB
60-100 players12-16 GB
100+ players16-32 GB

Jar filename

Java version

Advanced options

Headless (--nogui)

Run without the Swing GUI. Auto-disabled for proxies.

Show full stack traces

Adds -XX:-OmitStackTraceInFastThrow so repeated exceptions still print stacks.

Auto-restart loop

Wraps the script in a while/goto loop so the server restarts after a crash.

Use script variables

Emits fileName= and memory= variables at the top of the script for easy editing.

Calculate JVM overhead

Reduces -Xmx below the requested allocation to leave room for off-heap memory.

Large pages (HugeTLB)

Enables -XX:+UseLargePages. Requires kernel + Java support.

Generated start command

23 flags · Aikar / PaperMC

Download jar

start.sh

1#!/usr/bin/env bash
2set -euo pipefail
3
4java -Xms4096M -Xmx4096M -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -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 -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 -XX:-OmitStackTraceInFastThrow -jar paper.jar nogui
5

Flag breakdown

Memory

-Xms4096M
Initial heap size. Set equal to Xmx so the JVM doesn't grow on demand.
-Xmx4096M
Maximum heap size. Hard cap on the Java heap.

Preset flags

-XX:+UseG1GC
Garbage-First collector. Best general-purpose GC for Paper-family servers.
-XX:+ParallelRefProcEnabled
Parallelises reference processing during GC pauses.
-XX:MaxGCPauseMillis=200
Soft target for GC pause time. G1 will trade throughput to stay under it.
-XX:+UnlockExperimentalVMOptions
Allows experimental tuning flags.
-XX:+DisableExplicitGC
Ignores System.gc() calls from plugins/mods.
-XX:+AlwaysPreTouch
Touches every heap page on startup. Slower boot, smoother runtime.
-XX:G1HeapWastePercent=5
Waste threshold before mixed GCs are triggered.
-XX:G1MixedGCCountTarget=4
Number of mixed GC cycles to drain old-generation garbage.
-XX:InitiatingHeapOccupancyPercent=15
Heap occupancy that triggers a concurrent GC cycle.
-XX:G1MixedGCLiveThresholdPercent=90
Live data threshold above which a region is skipped during mixed GC.
-XX:G1RSetUpdatingPauseTimePercent=5
Maximum pause time spent updating remembered sets.
-XX:SurvivorRatio=32
Eden:Survivor space ratio. 32 keeps short-lived objects from promoting too fast.
-XX:+PerfDisableSharedMem
Disables /tmp/hsperfdata files; avoids stalls on slow disks.
-XX:MaxTenuringThreshold=1
Promote survivor objects to old gen after N collections.
-Dusing.aikars.flags=https://mcflags.emc.gs
Marker constant Aikar's flags look for at startup.
-Daikars.new.flags=true
Enables Paper's tuned defaults that match these flags.
-XX:G1NewSizePercent=30
Minimum young generation as % of heap. Higher = better throughput, more pauses.
-XX:G1MaxNewSizePercent=40
Maximum young generation as % of heap.
-XX:G1HeapRegionSize=8M
G1 region granularity. 8M for ≤12 GB heaps, 16M above.
-XX:G1ReservePercent=20
Heap percentage kept as a reserve for evacuation failures.

System / debug

-XX:-OmitStackTraceInFastThrow
Forces full stack traces, even for repeated exceptions.