-Xmx in ProjectZomboid64.json) from your plan’s memory: plan memory minus 1 GB on plans up to 5 GB, and 80% above 5 GB. A 4 GB plan gets 3072 MB. A value you edit is overwritten at the next start. For more memory, upgrade your plan.
How much RAM does Project Zomboid get on your server?
Project Zomboid runs on Java.-Xmx is the most memory Java may use for the game (the heap). Java also needs memory outside the heap, so the server keeps part of your plan’s memory free for it. Your plan’s memory is a hard limit: when the server goes over it, the server is stopped.
The rule: plans up to 5 GB get plan memory minus 1 GB; plans above 5 GB get 80% of plan memory.
Can I change -Xmx myself?
No. The server writes-Xmx into the vmArgs list of ProjectZomboid64.json every time it starts, so a value you edit by hand is overwritten at the next start. You can open the file in Files to see the current value, but you don’t need to edit it.
How to give Project Zomboid more memory
Java gets more memory when your plan has more memory. Upgrade your service to a plan with more memory, then restart the server. The new-Xmx is set automatically at that start.
Before you upgrade, check whether memory is the problem. More players, a larger explored map and more mods all use more memory.
How to check memory use on the Statistics page
1
Open Statistics
Click Statistics under ESSENTIALS.
2
Pick a time range
Choose 24h or 7d to see a normal day with players online.
3
Read the Memory chart
The Memory chart shows use over time. If it keeps climbing to your plan’s limit and the server restarts or stops, reduce mods or upgrade to a plan with more memory.
How much memory does Build 42 need?
In our tests, a 2 GB plan (1024 MB for Java) did not finish starting Project Zomboid Build 42. We recommend at least 4 GB of plan memory for Build 42, and more for many players or mods. See server won’t start for other causes of a failed start.Frequently asked questions
How do I allocate more RAM to Project Zomboid?
Upgrade to a plan with more memory and restart. The server sets-Xmx from your plan’s memory at every start, so editing ProjectZomboid64.json doesn’t change it.
Why did my -Xmx change back?
The server overwrites-Xmx in ProjectZomboid64.json at every start, based on your plan’s memory.
Is “Project Zomboid RAM allocation” in the game’s launcher the same?
No. The game client on your PC has its own memory setting. This page is about the server. Players set their own client memory on their PC.Do mods use more RAM?
Yes. Every mod, and especially map mods, adds memory use. Check the Statistics page after you add mods.Related guides
Project Zomboid guide
Every Project Zomboid page in one place.
Server won't start
Memory, disk space, map and mods.
Install mods
Add Workshop mods.
View server statistics
CPU, memory and network charts.
Zombie population
More zombies mean more to track.
Tested by the FREAKHOSTING team on 30 October 2026 (Project Zomboid Build 42 on our Game Panel). Steps may differ slightly if the game or its mods change.
Need Extra Help?
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Last Updated: October 2026