Project Zomboid Server Hosting: RAM, Mods and Map Growth

Project Zomboid server hosting looks cheap until the group scatters across Knox County, someone adds a Workshop collection and two map mods, and the server that was fine in week one stutters in week four. People ask which host performs best for a modded Project Zomboid server; mostly it comes down to three things no host does for you: enough RAM with a Java heap that fits the machine, a server on the same build as your players, and a world you can restore when an update or a mod breaks it.

This post covers which build to host in October 2026, what drives RAM and CPU, a sizing table with our prices and a heap setting per shape, a short Linux install, mods without mismatch errors, backups for long-running worlds, and where in Europe to put the server.

Which build to host: Build 42 is stable now

On 29 July 2026 The Indie Stone moved Build 42 to the public stable branch with version 42.20, multiplayer included, and 42.21 reached Stable on 28 September. A plain SteamCMD install of the dedicated server now gets Build 42. Build 41 lives on a beta branch called legacy41 (41.78.21 at the time of writing), and the Build 42 stable announcement is clear that Build 41 saves are not compatible with Build 42.

• New world: host Build 42 with the normal app_update 380870 validate.
• Existing Build 41 world, or a modpack not yet ported: use app_update 380870 -beta legacy41 validate, and have every player pick legacy41 under Properties, Game Versions & Betas in Steam.
• Unstable: the test branch for the next patch. Only if your whole group has opted in.

The rule underneath: client and server run the same build. Build 41 and Build 42 cannot join each other, and 42.21 added a message for players connecting to a server on a different version. When Steam updates the game for your players, update the server the same day.

What drives RAM and CPU on a Project Zomboid dedicated server

Player count alone is a weak predictor. The real drivers:

• How spread out players are. The server simulates the area around every connected player. Six people in one base is one busy area; six people in six towns is six.
• Zombie population. The sandbox population multiplier is 0.65 at Normal, 1.2 at High, 1.6 at Very High and 2.5 at Insane, and by default the population peaks at 1.5 times that on day 28. The game's own sandbox settings file strongly recommends leaving ZombiesCountBeforeDelete at its default of 300: raising it or setting it to 0 may cause severe performance problems.
• Mods, map mods first. A map mod adds cells to load and simulate. Vehicle and item packs add scripts and objects, and many mods run Lua on the server.
• World age. Explored parts of the map are written into the save, so an old world with several bases is heavier to load and bigger to back up.

Then the heap. The server is a Java process, and -Xmx caps its heap, but the process uses more than the heap, and the OS, SSH, SteamCMD and your backup job need room too. Set -Xmx to the whole VPS and the Linux out-of-memory killer ends the server, possibly mid-save. Our rule of thumb: leave about a quarter of the RAM, never less than 3 GB, outside the heap.

Two symptoms tell you which way you are wrong. java.lang.OutOfMemoryError in the console means the heap is too small. The java process vanishing with Out of memory: Killed process in dmesg means the heap is too big for the box.

Project Zomboid server requirements: a sizing table

We know of no official RAM table for the dedicated server, so these are rule-of-thumb starting points, not measurements. Prices are monthly on our standard KVM VPS; Bucharest is the base price and the other columns include the location fee.

Your server	Shape	RAM / vCPU / disk	-Xmx	Bucharest	Warsaw	Sofia, Vienna, Ashburn
4–6 friends, vanilla or a few QoL mods	VPS III	8 GB / 2 / 60 GB	5g	€10	€14	€16
10–16 players, light mods	VPS IV	16 GB / 4 / 80 GB	12g	€16	€24	€26
20–32 players, heavy modpack plus map mods	VPS V	24 GB / 6 / 100 GB	18g	€30	€42	€44
20–32 players, several map mods, world months old	VPS VI	32 GB / 8 / 120 GB	24g	€58	€74	€78

We would not start a Build 42 world you plan to keep on less than 8 GB. The default MaxPlayers is 32, where the bottom two rows sit, and each row down adds vCPUs as well as RAM. Traffic is unmetered, shaped at 180, 220, 260 and 300 Mbps for VPS III to VI. Our VPS sizing guide covers the general reasoning.

Unsure of your row? Load the real modpack onto an hourly VPS for an evening: a VPS IV is €0.0222 an hour in Bucharest, a started hour is billed as a full hour, and you need €5 of account credit to create one. Destroy it afterwards, because a powered-off VPS still bills. Outgrow a shape and you upgrade from the panel, then raise -Xmx.

Install a Project Zomboid server on Linux

These steps follow the official PZwiki dedicated server page on Ubuntu LTS. SteamCMD and a dedicated user first, because the server should not run as root:

sudo add-apt-repository multiverse
sudo dpkg --add-architecture i386
sudo apt update
sudo apt install steamcmd
sudo adduser pzuser
sudo mkdir /opt/pzserver
sudo chown pzuser:pzuser /opt/pzserver
sudo -u pzuser -i

As pzuser, write an update script and run it; the same command updates the server later. For Build 41, use the -beta legacy41 line from above.

cat > $HOME/update_zomboid.txt <<'EOL'
@ShutdownOnFailedCommand 1
@NoPromptForPassword 1
force_install_dir /opt/pzserver/
login anonymous
app_update 380870 validate
quit
EOL
export PATH=$PATH:/usr/games
steamcmd +runscript $HOME/update_zomboid.txt

Set the heap. On Linux, start-server.sh starts a launcher that reads its JVM arguments, -Xmx included, from ProjectZomboid64.json in the install folder:

grep -n '"-Xm' /opt/pzserver/ProjectZomboid64.json
sed -i -e 's/"-Xmx[0-9]*[mMgG]"/"-Xmx12g"/' -e 's/"-Xms[0-9]*[mMgG]"/"-Xms12g"/' /opt/pzserver/ProjectZomboid64.json

Swap 12g for the -Xmx in your table row (12g is VPS IV). The second expression lowers -Xms to match; PZwiki notes the Build 42 server ships with 16 GB of starting memory, and a starting heap above -Xmx stops the JVM from launching. An update with validate restores modified game files to how they shipped, so re-check this file after every update. Then, from your sudo account rather than pzuser, open 16261/UDP and 16262/UDP, allowing SSH before you enable the firewall:

sudo ufw allow 22/tcp
sudo ufw allow 16261/udp
sudo ufw allow 16262/udp
sudo ufw enable

First run, as pzuser, inside tmux so the console survives a dropped SSH session:

tmux new -s pz
cd /opt/pzserver
bash start-server.sh

On first start the server asks you to set the admin password, then generates a world with default settings. Detach with Ctrl-b then d; reattach with tmux attach -t pz. Typing save then quit stops it cleanly. The wiki documents a systemd unit too, but notes the developers discourage it, so we stay with tmux. RCON is set by RCONPort (default 27015) and RCONPassword; if you use it, keep that port closed to the internet.

Modded Project Zomboid server without mismatch errors

Settings live in ~/Zomboid/Server/servertest.ini, next to the sandbox and spawn Lua files. Mods use three lines:

WorkshopItems=514427485;513111049
Mods=\FirstModID;\SecondModID
Map=YourMapFolder;Muldraugh, KY

• Workshop IDs are not Mod IDs. WorkshopItems= takes numeric Steam Workshop IDs and tells the server what to download. Mods= takes the text ID each mod declares, and one Workshop item can contain several.
• Map mods also go in Map=, listed ahead of Muldraugh, KY. Adding or removing a map on a running world can cause trouble at the map edges, so back up first.
• Load order is line order. Frameworks and libraries go before the mods that need them.
• Let the game write the file. On Build 42 every ID in Mods= starts with a backslash, as above. A Build 41 list without them loads nothing on a Build 42 server, and no error appears. On a legacy41 server, leave the backslashes out. The safe route is to build the setup in the game's Host, Manage Settings screen on your PC, then copy servertest.ini and its Lua files to the server.
• Identical lists on both sides. Players download the server's Workshop mods automatically on connect, and DoLuaChecksum=true kicks anyone whose files differ.
• Restart after mod updates. When an author pushes an update, players get the new version, and a server still on the old one refuses them with "workshop item version is different than server's". A restart pulls the update, so schedule one rather than waiting for complaints.

Backups and long-running worlds

A Zomboid world becomes valuable slowly and breaks quickly. Everything is under ~/Zomboid: configs in Server/, the world in Saves/Multiplayer/servertest, and the server database in db/.

The server's own options (BackupsOnStart, BackupsOnVersionChange, BackupsCount) are worth leaving on for quick rollbacks, but they sit on the same disk as the world. Our VPS has no client snapshots either: there is own-image capture, up to 3 images per account at €0.06/GB a month, which suits a whole-machine copy before a big change, not nightly history. So send file-level backups off the box, telling the server to save first:

tmux send-keys -t pz "save" Enter
sleep 30
restic -r sftp:backup@your-backup-host:/srv/restic/pz backup /home/pzuser/Zomboid

Run it from cron, keep the repository in another country, and keep one copy from before every game update. Our guide to a restic or Borg backup VPS covers the receiving end.

Project Zomboid server in Europe: where to put it

Put the server in the city at the middle of your player base. Bucharest, Warsaw, Sofia, Vienna and Ashburn are priced in the sizing table above; Frankfurt costs the same as Sofia and Amsterdam the same as Warsaw. Stock varies by location, so check the order page. Ashburn is for North American groups and is in the United States, outside the EU. We do not publish latency figures, so test from your own connections on an hourly machine first. Every VPS runs on our own network, AS60982, with 100 Gbps DDoS protection included, on enterprise SSD with ZFS: SATA in Europe, NVMe in Ashburn.

What this is not

• Not managed Project Zomboid hosting, yet. Managed game servers are coming soon on our game hosting page and cannot be ordered today. On a VPS, updates, mods, backups and the heap are yours.
• Linux, not Windows. Our European VPS images are Linux and FreeBSD only (Windows Server VPS are sold only in Ashburn, US), so you run start-server.sh, not the batch files.
• No snapshots. Own-image capture only; file-level backups are your safety net.
• A disk ceiling. The largest VPS disk is 270 GB: 120 GB on VPS VI plus three 50 GB add-ons at €4 a month each. Plenty for Zomboid, but a hard limit.

How Noded Can Help

For most groups the starting point is a VPS IV in Bucharest, Warsaw or Sofia on Ubuntu LTS, with -Xmx12g, the Steam branch your players use, and a nightly restic job to a second location. It deploys in about a minute with full root and no setup fee; order it from the VPS hosting page, hourly to test or monthly once the world is permanent. If your group runs other survival games, the Valheim and 7 Days to Die sizing guides use the same reasoning. For a second opinion on a modpack, open a ticket or start a live chat.

FAQ

How much RAM does a Project Zomboid server need?

As a rule of thumb, 8 GB for a few friends on vanilla, 16 GB for 10–16 players with light mods, and 24–32 GB for 20–32 players with heavy modpacks and map mods. Player spread and zombie population matter as much as headcount.

Should my server run Build 41 or Build 42?

Build 42 has been the stable branch since 29 July 2026 and is the default for new worlds. Run Build 41 from the legacy41 beta only to continue a Build 41 world or modpack, with every player on the same branch.

Which ports does a Project Zomboid dedicated server use?

16261/UDP and 16262/UDP by default. RCON, if you enable it, defaults to 27015 and should stay closed to the public internet.

Where do I set the Java heap on a Linux Zomboid server?

In the -Xmx entry of ProjectZomboid64.json in the install folder, which start-server.sh reads. Leave about a quarter of the RAM free and re-check it after every SteamCMD update.

Does Noded offer managed Project Zomboid hosting?

Not yet; managed game hosting is coming soon. Today you run your own server on a Linux VPS with full root, unmetered traffic and DDoS protection included.