Optimizing Minecraft server performance: JVM flags & fixing TPS issues

Stutters, delays when breaking blocks, mobs that "teleport" around – almost always the cause is low TPS. The good news: most performance problems on a Minecraft server can be greatly reduced with the right server software, proper JVM flags and a few config values. This guide walks you through finding and fixing the causes step by step.

What is TPS – and why is my server lagging?

TPS stands for Ticks per Second. A Minecraft server calculates the world 20 times per second – so the target is 20 TPS. If the value drops below that, the world runs slower than real time: the server "hangs".

Just as important is MSPT (Milliseconds per Tick) – how long the server takes for one tick. At 20 TPS you have 50 ms per tick. Values consistently above 50 ms mean lag.

Value	Meaning
20 TPS / < 40 ms MSPT	Everything optimal
18–20 TPS	Light load, usually fine
< 18 TPS	Noticeable lag – find the cause
< 10 TPS	Server struggling, act urgently

Tip

Check current performance in-game with /tps and /mspt (available on Paper and its forks). That's always the first step when troubleshooting lag.

Step 1: Choose the right server software

The biggest performance jump often comes simply from switching server software. Vanilla and Spigot are significantly slower than modern forks:

Software	Recommendation
Vanilla	Purists only – barely optimized
Spigot	Better than Vanilla, but dated
Paper	Recommended standard – fast & compatible
Purpur / Pufferfish	Paper forks with even more tuning options

For most servers, Paper is the best choice: high plugin compatibility and noticeably better performance than Spigot.

Step 2: Java version & memory

Modern Minecraft versions require an up-to-date Java version:

Minecraft 1.17–1.20.4 → Java 17
Minecraft 1.20.5 and newer → Java 21

For RAM the rule is: as much as needed, not as much as possible. Over-allocating memory lengthens garbage collection pauses and can actually cause more lag.

Info

Set -Xms and -Xmx to the same value (e.g. both 4 GB). That way the JVM doesn't constantly grow/shrink the heap, which avoids stutters.

A rough RAM guideline (without large modpacks):

Players	Recommended RAM
1–5	2–3 GB
5–15	4–6 GB
15–40	6–10 GB
Modpacks	8 GB and up

Step 3: Aikar's Flags – the optimal JVM startup parameters

The default JVM settings aren't ideal for Minecraft. Aikar's Flags are a proven set of startup parameters that tune the garbage collector (G1GC) to minimize lag spikes. Add them as your server's startup parameters (example for 4 GB):

java -Xms4G -Xmx4G --add-modules=jdk.incubator.vector -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 -jar server.jar --nogui

Adjust -Xms and -Xmx to your RAM. From 12 GB upwards, also change these values:

-XX:G1NewSizePercent=40
-XX:G1MaxNewSizePercent=50
-XX:G1HeapRegionSize=16M
-XX:G1ReservePercent=15
-XX:InitiatingHeapOccupancyPercent=20

Info

Don't copy "miracle flags" from random forums. Many outdated or aggressive combinations do more harm than good. Aikar's Flags are the tested standard.

Step 4: Find the causes of poor TPS

Don't guess – measure. The spark plugin shows you exactly what's slowing the server down:

Install spark as a plugin
Run /spark profiler start and let it run for a few minutes
Run /spark profiler stop – you get a link with a detailed breakdown

This immediately shows whether entities, a specific plugin or world generation is causing the load.

Step 5: Common lag causes & fixes

Cause	Fix
Too many entities (mob farms, items)	Lower mob limits, check item despawn
View/simulation distance too high	Reduce in `server.properties`
Redstone & hopper machines	Limit the count, use hopper alternatives
Too many or bad plugins	Remove unused ones, check with spark
Chunks generated on the fly	Pre-generate the world with Chunky
Too little/too much RAM	Match allocation to player count

Step 6: Fine-tune server.properties & Paper config

Two values in server.properties have the biggest effect:

view-distance=8
simulation-distance=6

view-distance = how far players can see. 10 is default; 8 saves a lot of load with barely any visible difference.
simulation-distance = how far away the world actively "ticks" (mobs, growth). 6 is a good compromise.

In the Paper configuration (config/paper-world-defaults.yml), a lower mob-spawn-range and adjusted entity activation range also help – verify the values against spark.

Info

After changing startup parameters or config files, restart the server in the client area for them to take effect.

Quick checklist

Use Paper (instead of Vanilla/Spigot)
Pick the correct Java version (17 or 21)
-Xms = -Xmx, match RAM to player count
Set Aikar's Flags as startup parameters
Measure with /tps and spark instead of guessing
Lower view-distance and simulation-distance
Pre-generate the world with Chunky

With these steps you'll get the most out of your server. If your current machine is permanently at its limit, the only remaining fix is more power – then it's worth looking at a more powerful game server.