Project Zomboid SandboxVars.lua Settings Explained (Build 42)

What SandboxVars.lua is, where it lives, and how it differs from servertest.ini

For a dedicated server, the sandbox file sits in the server config folder: on Windows that is C:\Users\<you>\Zomboid\Server, and on Linux it is ~/Zomboid/Server. With the default server name, the file is servertest_SandboxVars.lua. If you start the server with -servername NAME, the file becomes NAME_SandboxVars.lua, alongside NAME.ini, NAME_spawnpoints.lua and NAME_spawnregions.lua.

Use SandboxVars for world rules. Use the servertest.ini settings reference for connection, visibility, save, mods and general server behaviour. That split matters because servertest.ini can be reloaded with reloadoptions, but sandbox changes need a full restart.

The file is a Lua table, so the structure matters:

• It starts with SandboxVars = { and ends with a matching }.
• Each setting is written as Key = value,.
• Nested groups use their own braces, such as ZombieConfig = { ... }, ZombieLore = { ... } and MultiplierConfig = { ... }.
• Numbers and booleans are not quoted. Text strings stay in quotes.

The most common mistakes that stop the server using the file are simple syntax errors: a missing comma between lines, a missing closing brace in a nested section, broken or mismatched quotes, or editing the wrong file for the active server name. Copy the file before you touch it. On a rented server, keep that copy on your own PC too, so a bad upload never leaves you guessing what changed.

How numbered option values work

Many sandbox settings are not stored as words like “Normal” or “Low”. They are stored as numbers that pick an option from the in-game menu. Host panels show the friendly label; the file stores the number. The lists below and in the reference table give every option’s meaning.

SandboxVars = {
    VERSION = 6,
    -- Default = Normal
    -- 1 = Insane, 2 = Very High, 3 = High
    -- 4 = Normal, 5 = Low, 6 = None
    Zombies = 4,
    -- Default = None
    -- 1 = High, 2 = Normal, 3 = Low, 4 = None
    ZombieRespawn = 4,
}

That means Zombies = 4 is not “four times the zombies”. It means “use the preset labelled Normal”. Read every number as a raw amount and you will get the world wrong. Notice too that a higher number can mean fewer zombies.

Build 42 also mixes preset choices with advanced values. A top-level preset such as Zombies also sets the advanced PopulationMultiplier under ZombieConfig: Insane is 2.5, Very High 1.6, High 1.2, Normal 0.65, Low 0.15 and None 0. Type your own number into PopulationMultiplier and that custom value is what the world uses. The rest of the file follows the same pattern: some lines pick a menu option, some are true or false, and some are plain multipliers, hours or days.

Practical rule: read the comment first, then decide whether you want the preset choice or the advanced field beneath it. If you use a host panel editor, save once and open the file afterwards to see which lines it changed.

Every SandboxVars setting, by group

Search any key or word below. Each group opens on its own, and the nested groups are listed separately. Keep the structure in mind as you edit: top-level settings cover broad world rules, while nested groups such as ZombieConfig, ZombieLore, Map and MultiplierConfig hold the detailed controls.

When sandbox changes apply on an existing world

Sandbox changes need a server restart. After the restart, the new file is active, but that does not mean every existing part of the world is rewritten. Some settings act when something is first generated or first found, and some timers count forward from the world’s start date and age.

The clearest examples are the looted-building settings. MaximumLooted (25) and RuralLooted (0.5) set the chance a building is already looted “when found”, rising over DaysUntilMaximumLooted (90 days). Buildings players have already found keep what they rolled. Loot multipliers work the same way: containers that have already spawned their contents won’t be re-rolled. Water and power shut-off are counted in days from the start date (9 July 1993 by default), so on a world past day 14 with the defaults, raising them won’t bring the power back.

Rule of thumb for mid-world edits: settings that run continuously apply from the restart onwards, while settings tied to first discovery or world age only show up in unexplored areas or future days.

If you need those rules to apply everywhere, the clean answer is a fresh world or a targeted area reset. The separate map reset and wipe guide covers when to wipe the whole save, reset only an area, or leave the world intact and accept mixed old and new rules.

The Build 42 population ramp and why week-by-week load changes

On Build 42 defaults, zombie population does not stay flat from day one. The advanced population section starts at PopulationStartMultiplier = 1.0, rises to PopulationPeakMultiplier = 1.5, and reaches that peak on PopulationPeakDay = 28.

ZombieConfig = {
  PopulationMultiplier = 0.65,
  PopulationStartMultiplier = 1.0,
  PopulationPeakMultiplier = 1.5,
  PopulationPeakDay = 28,
}

So the desired population on day 28 is half as high again as on day one, before you change anything. That is why a new server can feel fine for the first week and heavier by the fourth.

As the desired population rises, the server has more zombies to simulate in every loaded area, and players spread across several towns keep several areas loaded at once. If your group starts seeing hitches a few weeks in rather than on day one, the ramp is a likely part of it. To flatten it, bring PopulationPeakMultiplier down towards PopulationStartMultiplier, or push PopulationPeakDay later to slow the climb.

That is why population tuning and memory planning belong together. If the server is already showing later-world stutters, check the Project Zomboid server lag guide for other causes of server load, and the server RAM guide if the heap is likely too tight for the current world and player spread.

Tune the sandbox first, or move to a larger server?

If the world rules are simply heavier than your server can carry, these are the lines that make the biggest difference, and what players will notice when you change them.

If you have already trimmed these and the server still runs out of headroom as the world grows, more server is the better answer than a thinner world.

Loot multipliers: what the per-category values actually cover

The Build 42 loot categories are much more granular than the old broad loot presets. The per-category values below are direct multipliers with a range of 0.00 to 4.00. Raising one changes spawn chances for that category when a container is first filled. The exception is RollsMultiplier, which changes how many times the loot tables are rolled. The game’s own note says not to change it, because it can hurt performance.

For server admins, the useful habit is to change category multipliers, not the global roll count. Category multipliers alter what can appear within normal generation rules. RollsMultiplier makes the server do more work every time a container is filled, so it is the one most likely to turn “more loot” into “more load”.

Time, utilities and XP: the settings that change pacing without changing server load much

DayLength, StartTime, DayNightCycle, ClimateCycle and related time settings change how the world moves forward. They shape the experience, not the server load.

Utilities are split between preset choices and exact modifiers. WaterShut, ElecShut and AlarmDecay choose menu-style ranges, while WaterShutModifier, ElecShutModifier and AlarmDecayModifier let you set an exact number of days after the start date (default 14). Because they count from the start date, changing them on an old save only matters if that day hasn’t passed yet.

XP lives mostly in MultiplierConfig. If GlobalToggle = true, all skills use Global. If you turn that off, individual skill rates can differ. Global defaults to 1.0. XP changes progression without adding anything for the server to simulate.

Editing safely on a live server

Five steps that avoid both syntax mistakes and panel overwrites:

1. Stop the server fully.
2. Make a backup of the current config and, ideally, the current world save as well. If you need a fuller routine, the separate backup and restore guide covers the built-in backups and manual copies.
3. Edit the correct NAME_SandboxVars.lua file for the active -servername.
4. Start the server again.
5. Open the file again once the server is up, to make sure your change is still there.

If Lua syntax worries you, the safest route is to use the game’s Host -> Manage Settings sandbox editor on a local install to produce a valid file, then upload that finished NAME_SandboxVars.lua to the rented server. This is especially useful for nested sections and advanced values because the editor writes the braces, commas and value types correctly. Just make sure the file name matches the actual server name in use on the dedicated machine.

Symptoms, likely causes, and the first fix to try

Project Zomboid server FAQ

Where is the sandbox file on a dedicated server?

It is in the server config folder under the Zomboid user data directory: C:\Users\<you>\Zomboid\Server on Windows and ~/Zomboid/Server on Linux. With the default server name it is servertest_SandboxVars.lua. If you launch with -servername NAME, use NAME_SandboxVars.lua instead.

Do sandbox changes need a restart?

Yes. Sandbox changes are not like servertest.ini options that can be refreshed with reloadoptions. Edit the file, save it, and restart the server so the new Lua table is loaded.

Can I change sandbox settings on an existing world?

Yes, but not every change rewrites the existing world. Ongoing rules can affect future play after the restart, while settings tied to first discovery, first generation or world age may only apply cleanly to unexplored areas or future time. If you need total consistency, use a fresh world or a deliberate area reset.

Why did my server ignore my SandboxVars changes?

The usual reasons are editing the wrong file name, using the wrong server name, or having the host panel overwrite your manual edit on restart. The next most common cause is that the change was valid but you looked for it in already explored or already generated parts of the map. Check the active file name, restart, and judge generation settings in a fresh area.

What do the numbers in SandboxVars.lua mean?

Many are menu enums, not raw amounts. For example, a value such as Zombies = 4 means the preset labelled “Normal”, because the line’s comment defines the mapping. Other numbers are direct multipliers or timers, especially in advanced sections like ZombieConfig and MultiplierConfig.

More Project Zomboid server guides

The rest of our Project Zomboid server guides, plus the host comparison.