Project Zomboid Sandbox Settings Explained (Build 42)
Project Zomboid's sandbox settings live in a single file: servertest_SandboxVars.lua. Every gameplay knob — zombie population, loot rarity, XP rates, day length, weather — is controlled here. This is the most important file on your server. This guide explains every category and the settings that actually matter.
Critical: Stop the server before editing. PZ rewrites
SandboxVars.luaon shutdown and will overwrite your changes if you edit while running.
Where the file lives
/home/container/Zomboid/Server/servertest_SandboxVars.lua
If you renamed your server, replace servertest with your server name.
Population (zombie spawn rates)
These control how many zombies exist and where they spawn — the single biggest difficulty lever.
| Setting | Default | Range | What it does |
|---|---|---|---|
Population |
3 (Normal) | 1=Insane, 2=High, 3=Normal, 4=Low, 5=None | Master zombie multiplier |
PopulationStartMultiplier |
1.0 | 0.0–4.0 | Starting day population |
PopulationPeakMultiplier |
1.5 | 0.0–4.0 | Maximum population reached |
PopulationPeakDay |
28 | 1–365 | Day population peaks |
RespawnHours |
72.0 | 0–8760 | Hours before zombies respawn in cleared cells |
RespawnUnseenHours |
16.0 | 0–8760 | Hours a cell must be unseen before respawn |
RespawnMultiplier |
1.0 | 0.0–10.0 | Multiplier on respawn count |
Practical tuning: For a forgiving server, set PopulationPeakMultiplier to 0.6 and RespawnHours to 168 (one week). For a brutal server, peak to 3.0 and respawn to 24.
Loot
Controls how much loot spawns and where.
| Setting | Default | Effect |
|---|---|---|
FoodLoot |
2 (Normal) | 1=Extremely Rare, 5=Abundant |
WeaponLoot |
2 | Same scale |
OtherLoot |
2 | Same scale (clothing, electronics, etc.) |
LootRespawn |
1 (None) | 1=None, 2=Every Day, 3=Every Week, 4=Every Month, 5=Every 2 Months, 6=Every 6 Months |
SeenHoursPreventLootRespawn |
0 | Prevents respawn in containers seen within N hours |
HoursForLootRespawn |
0 | Hours of game time before any container can respawn loot |
For long-running servers: Set LootRespawn to 4 (Every Month) and SeenHoursPreventLootRespawn to 24. Otherwise players strip the map permanently within a week.
Survival mechanics
| Setting | Default | Notes |
|---|---|---|
HoursPerDay |
1 (1 hour) | 1=15 min, 2=30 min, 3=1 hour, 4=2 hours, 5=3 hours, 6=Real Time |
StartTime |
2 (9AM) | 1=7AM, 2=9AM, 3=12PM, 4=2PM, 5=5PM, 6=9PM, 7=12AM |
StartMonth |
7 (July) | 1–12 |
StartDay |
9 | 1–28 |
WaterShut |
2 (0–30 days) | When mains water cuts off |
ElecShut |
2 (0–30 days) | When power cuts off |
WaterShutModifier |
14 | Days into the range when water cuts |
ElecShutModifier |
14 | Days into the range when power cuts |
Long-running servers: Push WaterShutModifier and ElecShutModifier to 60+ days. Otherwise players spend month two purely scavenging water.
Zombie behaviour (the difficulty knobs)
| Setting | Default | Effect |
|---|---|---|
Speed |
2 (Fast Shamblers) | 1=Sprinters, 2=Fast Shamblers, 3=Shamblers |
Strength |
2 (Normal) | 1=Superhuman, 2=Normal, 3=Weak |
Toughness |
2 (Normal) | Same scale |
Transmission |
1 (Bite Only) | 1=Bite Only, 2=Bite + Saliva, 3=Everyone Infected, 4=No Transmission |
Mortality |
5 (0–30 seconds) | How fast infection kills |
Reanimate |
3 (0–1 minute) | How fast corpses turn |
Cognition |
3 (Basic Navigation) | Pathing intelligence |
MemoryDuration |
2 (Normal) | How long zombies remember a target |
Sight |
2 (Normal) | 1=Eagle, 2=Normal, 3=Poor |
Hearing |
2 (Normal) | Same scale |
Smell |
2 (Normal) | Same scale |
Build 42.17 note: Sprinters are now stable in multiplayer as of April 2026 — set Speed=1 for the highest-difficulty experience.
Combat & XP
| Setting | Default | Effect |
|---|---|---|
XpMultiplier |
1.0 | Global XP gain |
XPMultiplierAffectsPassive |
false | Apply XP multiplier to passive skills (Fitness, Strength) |
MeleeStunChanceMultiplier |
1.0 | Knockdown chance on melee hits |
Vehicles (Build 42 has new vehicle handling)
| Setting | Default | Effect |
|---|---|---|
CarSpawnRate |
3 (Normal) | 1=Low, 2=Lower, 3=Normal, 4=High |
ChanceHasGas |
3 | Likelihood vehicles have fuel |
InitialGas |
3 | Starting fuel level |
VehicleEasyUse |
false | Removes vehicle skill requirement |
Building (Build 42 — basements & taller buildings)
| Setting | Default | Effect |
|---|---|---|
ConstructionBonusPoints |
3 (Normal) | XP gain from construction |
AllClothesUnlocked |
false | Skip clothing requirements |
MaxFogIntensity |
1.0 | 0.0 disables fog entirely |
MaxRainFxIntensity |
1.0 | 0.0 disables rain FX |
EnableSnowOnGround |
true | Visual snow during winter |
Editing the file safely
- Stop the server from your panel (this is non-negotiable)
- Open
/home/container/Zomboid/Server/servertest_SandboxVars.luain the file manager or via SFTP - Find the setting you want by Ctrl+F
- Change only the number after
=— leave the comma and key name alone - Save the file
- Start the server
The values must match Lua syntax: Speed = 2, not Speed = "Fast Shamblers".
Apply changes without a wipe
Sandbox settings are read on world creation, so most settings only affect new chunks. Settings that do apply to existing worlds:
- Population multipliers (after
RespawnUnseenHours) - All zombie behavior (
Speed,Strength,Cognition, etc.) - Loot respawn settings
- XP multipliers
Settings that don't affect existing worlds:
StartMonth,StartDay,StartTime- Initial loot density (only respawned loot is affected)
- Map-wide weather defaults
Sandbox presets
Project Zomboid ships with built-in presets you can apply via the in-game Custom Sandbox menu before generating a world: Apocalypse (default), Survivor, Survival, Builder, Initial Infection, Six Months Later. On a dedicated server, copy the preset values from a singleplayer save and paste into your SandboxVars.lua.
FAQ
My changes keep getting reverted. You edited while the server was running. PZ saved its in-memory state on shutdown and overwrote your file. Always stop the server first.
Can I change settings live with /changeoption? Only a small subset (PVP, max players, voice settings) can be changed live. Sandbox values cannot — they require a restart.
Where can I find the full vanilla defaults?
Generate a fresh server (the panel does this on first boot), and SandboxVars.lua will appear with every default set. Use it as a reference before customizing.
Will higher zombie population hurt server performance?
Yes — significantly. Doubling PopulationPeakMultiplier adds roughly 30% to RAM usage and CPU load. Plan with our RAM calculator.
Do mods add their own sandbox settings?
Some do. Mods like ModOptions, True Music, and ORGM register additional fields automatically when loaded. They appear at the bottom of SandboxVars.lua after the next server start.