For a friends-only Project Zomboid Build 42 server, start with a password-protected co-op world: set PVP=false, Open=true, PauseEmpty=true, and MaxPlayers to your real expected group size. Use low-to-normal zombie population, disable respawn, choose shamblers, raise loot slightly, set global XP to 2–3x, and make the day two hours or longer. Give every player the same Build 42 branch, then test the world with one account before inviting everyone. This combination keeps a shared save forgiving without removing the survival systems that make Project Zomboid interesting.
The exact file names, setting scales and mod keys changed in Build 42, so an old Build 41 snippet can silently produce the wrong world. The sections below show which files to edit, what each important option does, and when hosting from a dedicated process is a better choice than running a game-hosted session.
Which files control a Project Zomboid multiplayer server?
The active server files live in the user profile’s Zomboid/Server directory. The name before each extension must match the server name supplied by the startup option -servername. With the usual name, the files are:
servertest.inicontrols the multiplayer shell: who may join, whether the server is public, player capacity, pausing and safehouses.servertest_SandboxVars.luacontrols the simulated apocalypse: zombies, loot, infection, experience, day length and utility shutdowns.
If the server was started with a different name, replace servertest in both filenames with that value. Editing a similarly named file while the process loads another one is the most common reason a change appears to do nothing. Build 42 also renamed several keys and changed their scales; use the Build 42 structure rather than copying a Build 41 configuration.
How should I configure the multiplayer shell for friends?
These options determine access and the rules that apply before the world-simulation settings are considered.
Make the server private without maintaining a manual whitelist
Set Password to a secret shared only with your group. Set Open=true so passworded accounts can join without you approving each account manually. Keep Public=false for a friends-only world; when listing is desired, Public=true and PublicName control how it appears in the server browser. A password is still needed for a private group even if the server is not listed.
Turn off player-versus-player damage
Set PVP=false for a pure co-op baseline. If you enable PvP, the safety system and its timers govern individual player toggles, so a player may not be able to attack immediately or may retain protection after changing the option. Decide this before the first session; it changes the social rules of the save more than any loot multiplier does.
Stop the clock while everyone is offline
Set PauseEmpty=true when the group plays on a schedule. The world stops advancing while no players are connected, preventing crops, generators and character needs from progressing during a period when nobody can respond. Leave it off only if you deliberately want an always-running world in which unattended time is part of the challenge.
Set capacity to the group you actually have
Set MaxPlayers to the largest number of people likely to be online together, not an aspirational community size. A lower, realistic value reduces accidental load and makes connection problems easier to diagnose. Build 42 documentation describes a 254-player ceiling, but that is an engine limit, not a performance guarantee. Another 2026 guide uses 32 players as a documented default and a practical warning point; zombie simulation, mods and map activity can make a much smaller group demanding.
Choose safehouse rules before players claim bases
Safehouse options control whether players may claim a building, whether outsiders can enter or loot it, and whether a death can respawn a character there. For a cooperative group, allow claims and protect interiors if you want a shared headquarters. If you want every building to remain contestable, disable protection. Decide whether safehouse respawn fits your tone: it shortens recovery after a death but can remove the risk of a long journey back.
When do I need to forward ports?
The dedicated-server guide documents UDP ports 16261 and 16262 as the defaults. Forward them only when players outside the local network cannot connect through the normal host setup. Port forwarding does not increase the server’s player capacity; it only makes the process reachable through your router. Keep the operating-system firewall and router rule limited to the machine running the server.
What Build 42 world settings make a good friends-only server?
Open servertest_SandboxVars.lua for these rules. Build 42 uses different names and ranges from Build 41, so verify every key against a Build 42-generated file.
Zombie population and respawn
The coarse Zombies setting runs from Insane through None. Build 42 also exposes a finer ZombieConfig.PopulationMultiplier; one documented reference reports 0.65 for the Build 42 Normal setting. Do not interpret that number as a universal percentage for Build 41, whose baseline was different.
For a relaxed group, choose Low or Normal and set respawn off. Respawn behavior is controlled by RespawnHours, RespawnUnseenHours and RespawnMultiplier. With respawn disabled, clearing a town creates a dependable safe route and lets new players catch up. If you want a living world without sudden re-invasions, use a long unseen interval and a low multiplier rather than a frequent full refill.
Zombie movement and infection
ZombieLore.Speed selects sprinters, fast shamblers, shamblers or a random mix. Shamblers are the most forgiving default: they punish noise and poor positioning but leave players time to react. Sprinters make a server dramatically less tolerant of lag, unfamiliar controls and split-up groups.
ZombieLore.Transmission controls blood-and-saliva transmission, saliva-only transmission, an everyone-infected mode or no transmission. Saliva-only is a useful friends preset because a bite remains consequential while scratches and incidental blood contact do not create as many arguments about invisible risk. Blood-and-saliva is the classic survival choice; no transmission turns infection into a non-factor rather than a resource-management problem.
Loot rarity in Build 42
Build 42 uses per-category multipliers such as FoodLootNew, WeaponLootNew and AmmoLootNew. Raise only the categories that are slowing your group. Slightly more food and medical supplies can help a large party, while leaving weapons near default preserves the need to search and repair. Build 41’s one-to-five rarity names do not map directly to these keys, so do not paste a Build 41 loot block into a Build 42 file.
Experience, day length and utilities
Set MultiplierConfig.Global to 2 or 3 for the relaxed friends profile; optional skill-specific overrides can keep a particular profession from accelerating too quickly. Use DayLength of two hours or longer when players explore together, build bases and still need time to sort loot. A longer day reduces the number of forced night trips without making every action instant.
WaterShut and ElecShut determine when those utilities fail. Keep the normal progression for classic survival, or delay the shutdown when new players need a protected learning period. Record any non-default values for the group: utility timing changes the value of generators, farming and stored water more than a small loot adjustment does.
Which preset should our group use?
The following starting points are practical configurations, not official in-game presets. Choose by how much downtime, recovery travel and pressure your group enjoys.
| Group goal | Zombies and respawn | Loot | XP | Day length | Infection |
|---|---|---|---|---|---|
| Relaxed friends | Low; respawn off | Above default | 2–3x global | 2 hours or longer | Saliva only |
| Classic survival | Normal; respawn off | Default | 1x | 1.5 hours | Blood and saliva |
| Long-run challenge | High; slow respawn | Below default | 1x | 1 hour | Blood and saliva |
Relaxed friends
Use this when players have mixed experience or only a few hours each week. Low population and no respawn make cleared routes meaningful; shamblers and saliva-only infection preserve danger. Above-default loot and 2–3x XP compensate for a party that divides jobs among several characters rather than repeating the same skill grind.
Classic survival
This is the neutral starting point for players who already know the controls. Normal population, default loot and 1x XP retain the intended scarcity. A 1.5-hour day gives enough daylight for a focused outing while keeping night planning important.
Long-run challenge
Choose this only when the group accepts slower recovery. High population and a slow respawn schedule keep pressure on established towns, while below-default loot makes specialization and trade valuable. A one-hour day increases the cost of every detour, so it suits players who coordinate schedules and routes.
How do I change Project Zomboid server settings safely?
Use this workflow whenever you edit either file.
- Identify the active name. Check the startup command for
-servername, then open only the matching INI and SandboxVars files inZomboid/Server. - Stop the server cleanly. Do not edit while the process is writing. Back up the INI, the SandboxVars file and the multiplayer save before changing anything.
- Change one related group. For example, adjust population and respawn together, or access and capacity together. Preserve the Lua punctuation, comments and surrounding structure.
- Save and restart. SandboxVars changes require a server restart. A running process will continue using the values it loaded at launch.
- Test with one account. Confirm the build number, join with a test character and check the intended behavior before inviting the group. Inspect access, PvP, pausing and a representative world rule.
- Keep a dated backup. If the result is worse, stop the server, restore the prior files and save, then restart. Do not overwrite the only copy of a world that contains valuable characters.
Already visited areas may retain values generated under the previous SandboxVars configuration. A population or loot change is therefore most obvious in unexplored cells; changing the file does not guarantee that an established town will be regenerated.
How should I configure Workshop mods on a Build 42 server?
Mods require four kinds of agreement: the server’s Build 42 branch, the numeric Workshop item, the mod’s internal ID and the load order.
WorkshopItemscontains the numeric Steam Workshop IDs.Modscontains each mod’sid=value from itsmod.info, not its display name.Mapcontains map entries when a map mod requires them.- List dependencies before the mods that depend on them.
Separate entries with semicolons and do not add spaces. Confirm that every item targets the same Build 42 branch as the server and clients. Players download the server’s Workshop items when they join, but a wrong ID, missing dependency or incompatible branch can still stop loading or produce a different world. Add one mod at a time, restart and test before expanding the collection.
Should I host from my PC or run a dedicated server?
An in-game host is convenient for short sessions: one player launches the world and friends connect. The world stops being available when that host closes the game, so it works best when everyone plays at the same time.
A dedicated process keeps the world online while all players are offline and lets the host machine run without a game client. It is better for scheduled drop-in play, but someone must maintain the process, backups, configuration and network access. Managed hosting can remove much of that administration, while a self-hosted dedicated process offers more direct control over files and restart timing.
Performance depends less on the headline player limit than on active simulation. Zombie population combined with respawn, the number of mods and realistic concurrent players are the main documented load levers. Players spread across several towns keep more map areas active than players sharing one base, increasing streaming and synchronization work. Start with the smallest capacity that fits the group and raise it only after a stable test.
What are the most common server-setting failures?
My setting had no effect
Check the -servername value and make sure both files use that exact name. Confirm the server was stopped before editing and restarted afterward. If only old towns look unchanged, test an unexplored area because generated cells can retain earlier values.
Friends cannot connect from outside my home
Verify that the server is listening on UDP 16261 and 16262, then check the router forward and operating-system firewall on the host machine. Local-network connections can work even when an internet connection fails, so test from a genuinely external network.
The server feels slow or desynchronizes
Lower zombie population or disable respawn first, then test with fewer Workshop items and the actual player count. Ask players to avoid spreading across many towns during diagnosis; concentrated activity makes it easier to identify whether map streaming is the bottleneck.
A mod downloads but does not load
Compare the numeric Workshop ID with the internal id= value, check dependency order and confirm Build 42 compatibility. Remove the newest item, restart and add it back only after the unmodded or previously stable set loads.
The world advances while nobody is online
Set PauseEmpty=true in the active INI, save it while the server is stopped and restart. If it still advances, you likely edited a different server-name file or are connecting to another process.
How can we change difficulty without restarting the whole campaign?
Make incremental changes and keep the save. Increase loot or XP before changing zombie speed, because those adjustments preserve the map’s geography and player knowledge. If the group wants a harder late game, reduce loot or add a slow respawn schedule rather than jumping straight to sprinters. For any major experiment, clone the save and test the clone so the main campaign remains recoverable.
Frequently Asked Questions
Can I use a Build 41 server configuration in Build 42?
Not safely. Build 42 changed population, loot and experience keys and their scales, so an old block may be ignored or represent a different difficulty. Generate a Build 42 file and transfer only settings you can match by name and meaning.
Will changing loot settings refill buildings we already searched?
Usually, no. Existing cells can retain values generated earlier, so a new multiplier is easiest to observe in unexplored areas. Treat a loot change as a rule for future generation, not a guaranteed reset of every container.
What happens when more players try to join than MaxPlayers allows?
The server rejects additional connections once the configured concurrent capacity is reached. Set the value to your realistic peak and raise it only after observing stable performance with the group and mod list you actually use.
Does PauseEmpty protect crops and generators while everyone is offline?
It stops the world clock when no players are connected, so time-dependent systems do not progress during that empty period. It does not undo events that occurred while somebody was still online.
Do clients need the same mods installed before joining?
They need compatible versions of the server’s Workshop items and the same Build 42 branch. The server can provide the listed Workshop downloads during connection, but an incorrect ID, missing dependency or incompatible client version still prevents a clean join.