Can I use custom startup flags (MaxRAMPercentage, -nogui, velocity flags, OpenJ9)?

You can customize startup flags on most servers, as long as the Startup tab exposes the command or flags for your server. For the majority of setups, though, the defaults are already the best choice.

What you can add

Where the Startup tab exposes the command and flags, you can add options such as:

• -nogui (already included in our startup).
• Proxy-specific flags for Velocity.
• Other JVM flags appropriate to your setup.

If the command is admin-locked on your server, open a ticket and we'll make the change for you.

Best practices

1. For most servers, leave the default Aikar/G1GC flags in place — they're already tuned well.
2. Only add custom flags when you have a specific reason.
3. Don't mix conflicting garbage-collector or memory flags.

Warning: Avoid combining flags that fight each other — for example, don't set -Xmx alongside MaxRAMPercentage. Pick one memory model, not both.

Frequently asked questions

Can I use MaxRAMPercentage or OpenJ9-style flags? You can add exposed flags, but avoid mixing memory models — combining -Xmx with MaxRAMPercentage conflicts. Stick to one approach.

What if my startup command is locked? Then it's admin-locked. Open a ticket describing the flags you need and we'll apply them.