Project Zomboid SandboxVars.lua options

<servername>_SandboxVars.lua holds the rules of a Project Zomboid world: how many zombies, how fast they move, how rare loot is, when the water and power go off, how long a day lasts and how quickly characters learn. It is a Lua table in Zomboid/Server/, read when the server starts. Most options are numbered positions on a scale rather than real quantities, and the scale is written in a comment above each line in the file the server generates - which makes that generated file the best documentation you have. The safest way to build one is to choose the settings in the game's own sandbox screen, host once from the client, and copy the resulting file to the server.

This guide goes through the file section by section: what each option does, what its values mean on Build 41, which ones a multiplayer server should actually think about, and which only take effect on a new world. For the server ini - ports, PvP, safehouses, mods - see Project Zomboid server settings.

How the file works#

SandboxVars = {    VERSION = 5,    -- Changing this also sets the "Population Multiplier" in Advanced Zombie Options.    -- Default=Normal 1 = Insane 2 = Very High 3 = High 4 = Normal 5 = Low 6 = None    Zombies = 4,    Distribution = 1,    DayLength = 3,    StartMonth = 7,    StartDay = 9,    StartTime = 2,    WaterShut = 2,    ElecShut = 2,    ZombieLore = {        Speed = 2,    },    ZombieConfig = {        PopulationMultiplier = 1.0,    },}

Three rules make editing it painless.

Every value has a comment above it. The generated file explains each scale, including which number is the default. Keep the comments. When a guide (including this one) and the comment disagree, the comment matches your build and wins.

The structure matters. It is a Lua table: options separated by commas, nested tables for ZombieLore and ZombieConfig, braces that must balance. A missing comma or brace stops the server from reading the file. The console shows the line where parsing failed.

Files are read at start. Edit with the server stopped, then start it. Changes made through the in-game admin panel's sandbox options apply to the running world and are saved into it, which means the world and the file can disagree - and the world wins. If you use the panel, write the same change into the file so the next person reading it is not misled. Project Zomboid admin commands covers the panel.

Population, time and the start#

Zombies runs from most to fewest, which surprises everyone once: 1 is Insane, not "one". It is a preset that sets PopulationMultiplier; if you also set the multiplier directly, the explicit value is what the server uses, so set one or the other deliberately.

DayLength is the most consequential setting on the server for how the game feels. At the default of one real hour per day, a two-hour session is two in-game days. Farming, healing, skill books and food spoiling all run on game time, so shorter days make the world move faster around players who are not online. For an evening group, one or two hours per day is the usual range. Very short days punish anybody who logs in less than the others.

StartMonth decides the season. The default July start gives a long summer to prepare for winter; starting in autumn or winter is a deliberate difficulty choice, because crops do not grow and cold arrives early.

Utilities: water and electricity#

The scale options choose a range; the modifier holds the actual day picked within it. On a server this is fixed when the world is created and counted from day one, so changing WaterShut on a running world does not restart the clock. Water and power going off are major milestones in a Zomboid world - fridges stop, taps run dry, the generator hunt begins - so this is a setting to agree on before the server opens.

Loot and loot respawn#

The rarity scale in most Build 41 releases runs from Extremely Rare to Abundant in five steps, and later releases added steps at the rare end. The comment shows which you have.

Split loot by category rather than moving everything together. A survival server that wants food to matter and guns to be rare but ammunition findable is three settings, not one. Literature is worth a thought of its own: skill books are the fastest progression in the game, and their rarity sets how quickly the group outgrows early challenges.

Loot respawn changes the long game more than any rarity setting. With LootRespawn at 1, the map is finite: what the group takes is gone, and after a few months the server needs a reset - covered in Project Zomboid server reset. With weekly or monthly respawn plus ConstructionPreventsLootRespawn, towns slowly refill while bases are left alone, which suits a public server where players come and go.

The world: weather, nature and events#

Helicopter deserves care on a multiplayer server. The event pulls large numbers of zombies along its path, and on a server where players are spread across the map, it can flatten one player's preparations while another sees nothing. Some groups switch it off for that reason; others consider it the best part of the first week.

Alarm and LockedHouses shape early play more than they seem to. Frequent alarms punish careless looting with a horde; frequent locked houses push players towards tools and windows.

FireSpread on a public server is a griefing question. With it on, one Molotov can burn down a street of player bases. Decide with your safehouse rules in mind.

Characters and progression#

XpMultiplier is the most-changed option in this section, and the most often overdone. Doubling it makes a server that plays a few evenings a week feel fair; multiplying it by ten turns the early game into a formality and leaves players with nothing to work towards after a fortnight. Remember that DayLength already affects progression, because reading and many actions take game time.

CharacterFreePoints is a softer alternative to raising XP. A few extra points let people take a positive trait or two without strong negative ones, which helps new players without changing the long game.

Vehicles#

Vehicles cost performance on a server, because driving loads chunks quickly. CarSpawnRate and the vehicle speed limit in the ini both matter; the performance side is covered in Project Zomboid server lag.

Zombie lore#

ZombieLore is a nested table, and it defines what a zombie is.

Speed is the headline. Sprinters on a multiplayer server are a novelty mode; they also look worse under latency, because fast movement exaggerates every bit of desync. Random mixes speeds and is a popular compromise.

Transmission and Mortality together decide whether a bite is a death sentence. Vanilla is blood and saliva with death in two to three days, which makes every melee fight a real risk. Transmission = 4 removes infection entirely, which some groups prefer for a building-focused server.

Cognition = 1 gives zombies the ability to open doors. It changes how players secure bases and is worth announcing.

ThumpOnConstruction off makes player bases safe from zombies, which turns the game into a builder. Leaving it on keeps walls meaningful.

Zombie config: population over time#

Population starts at the start multiplier and rises to the peak by the peak day. A server that seems fine in week one gets harder and heavier through week four by design.

RespawnHours = 0 is the most common change on multiplayer servers. Without it, areas players cleared slowly refill, which on a server with several players who each cleared their own streets feels like running in place. With it off, the map is a resource the group works through. The cost is that the world gets quieter over months, which is what loot respawn or a scheduled reset are for.

Removal timers#

These matter for performance on a long-running server more than for gameplay. Corpses left for nine in-game days pile up outside bases after a fight.

Three worked examples#

Settings make more sense as a set than one at a time. These are three common server styles and the choices that define them.

The friends' server. Four to six people, a couple of evenings a week. Keep vanilla zombie lore so the game still feels like Zomboid, but set RespawnHours = 0 so the streets people clear stay cleared. Raise XpMultiplier to about 2 so the group sees progress between sessions, and choose a two-hour DayLength so an evening covers a day or so of game time rather than three. Put water and power on the 0-30 day range so the first real milestone arrives in the second or third week of play. Leave loot respawn off and plan a reset when the map runs dry. Pair it with PauseEmpty=true in the ini so the world waits for you.

The public survival server. Twenty or more players who come and go. Here the world must keep producing for newcomers, so loot respawn on a weekly or monthly cycle with ConstructionPreventsLootRespawn = true matters more than any rarity setting, and a low RespawnMultiplier keeps towns dangerous without refilling them completely. Keep XpMultiplier near 1 so long-term players have something to work towards. Turn FireSpread off unless your rules can handle arson, and think hard before enabling the helicopter event, which will hit some players and not others. Shorten HoursForCorpseRemoval for performance.

The hardcore server. For groups who want the game to be cruel. Speed = 4 for a random mix that includes sprinters, Cognition = 1 so doors are not safety, shorter utility shut-off, Rain and Temperature pushed towards the extremes, and an autumn StartMonth so winter arrives before the group is ready. Keep XpMultiplier at 1 and CharacterFreePoints at 0. It is worth telling people before they join, because a hardcore server that is not announced as one mostly produces complaints.

None of these is right for every group. What they show is that a server's character comes from a handful of choices made together, and that changing one option in isolation - doubling XP, turning on sprinters - often shifts the balance of the others more than expected. Change a few things, play a week, and adjust.

Building the file and applying it#

The reliable workflow:

1. In the game client, choose Host, then the sandbox settings, and set everything you want. Save it as a preset if you will reuse it.
2. Start the hosted game once and quit. The client writes servertest_SandboxVars.lua - named after the server name you used when hosting - into Zomboid/Server/ on your PC.
3. Stop the dedicated server.
4. Upload the file to the server's Zomboid/Server/ folder, renamed to match the server's -servername if needed. SFTP and the file manager covers the transfer.
5. Start the server and check a few values in the in-game admin panel.

Options tied to the world's creation - start date, utility shut-off timing - only fully take effect on a new world. Everything else applies to the existing world from the next start.

Troubleshooting#

The server ignores my sandbox file. It is named for a different server name, or it is in the install folder instead of Zomboid/Server/.

The server fails to start after an edit. A Lua syntax error, usually a missing comma. The console names the line.

A setting reverted after restart. It was changed in the admin panel and saved into the world, or the world kept a value from creation. Set it in both places.

Zombies are far more numerous than expected. Zombies runs backwards: 1 is Insane. Check PopulationMultiplier too.

Changing water and power shut-off did nothing. They are counted from the world's start. On an existing world, the original timing stands.

FAQ#

Where is the SandboxVars file on a server?

In Zomboid/Server/<servername>_SandboxVars.lua, beside the ini of the same name. The server name comes from -servername, and servertest is the default.

Can I change sandbox settings without a restart?

Through the in-game admin panel, yes, and the change is saved into the world. Edits to the file itself need a restart, and a few options tied to world creation only apply to a new world.

What are good settings for a group of friends?

A common starting point is vanilla zombies with Speed = 2, RespawnHours = 0, XpMultiplier between 1.5 and 3, DayLength of one or two hours, and loot respawn off. Then adjust after the first week.

Why do my values not match a guide I copied from?

Builds differ. Several scales gained extra steps during Build 41, and Build 42 changed many options. Use the comment above each line in your own generated file.

Does XpMultiplier affect fitness and strength?

Only if XpMultiplierAffectsPassive is true. By default the passive skills level at their normal, slow rate.

Do sandbox settings affect server performance?

Several do: zombie population and respawn, car spawn rate, and the corpse and item removal timers. Project Zomboid server lag covers which ones matter.