MineFixTools server utility lab
Tool 1 min read Updated

Minecraft JVM Flag Generator

Generate practical Minecraft server JVM flags for Paper, Purpur, Forge, Fabric, and Velocity with sensible heap sizing and GC reminders.

Performance and TPS java jvm flags performance startup

Generate JVM Flags

Use the generator as a starting point, then test during real player activity. JVM flags are not a substitute for profiling, plugin audits, sensible distances, or a good host.

When to Use Conservative Flags

Use conservative flags when you are recovering from a crash, changing Java versions, testing a new host, or comparing a panel startup command against SSH. Once the server is stable, tune carefully.

If a server fails before loading plugins, first test a minimal command:

java -Xms2G -Xmx2G -jar server.jar nogui

Then rebuild the startup command here. If exit code 1 returns, use the exit code 1 guide to find the first exception.

Keep Memory Realistic

Too little memory causes pressure. Too much memory can create longer pauses and hide the real workload. Leave memory for the operating system, panel, databases, proxy, backups, and file cache.

What to Check After Changing Flags

After updating flags, watch:

  1. Startup success.
  2. Heap usage under normal player count.
  3. Garbage collection pauses.
  4. TPS and MSPT during busy periods.
  5. Plugin or mod startup errors.

If TPS stays low while memory looks healthy, the problem is probably entities, chunks, plugins, or CPU. Start with the TPS drops guide.

FAQ

Should Xms and Xmx be the same?

For most dedicated Minecraft server processes, matching Xms and Xmx keeps heap sizing predictable.

Will flags fix low TPS?

Flags can reduce garbage collection problems, but low TPS often comes from CPU load, entities, chunks, or plugins.

How much memory should I choose?

Choose enough for your version, worlds, mods, and player count, then profile. Do not use all machine memory for the Java heap.

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