Why aren’t my Project Zomboid sandbox changes applying? Stop the server first, because it rewrites its sandbox file on shutdown and will overwrite edits made while it runs. Change the values in your server’s SandboxVars file (or the panel’s sandbox settings manager) and restart. On an existing world, changes mostly affect newly generated areas and new loot rolls, so places players already explored keep their old values.
Where do Project Zomboid sandbox settings live?
Sandbox settings are stored in a Lua file named after your server, such as servertest_SandboxVars.lua. It is separate from the server.ini file, which holds server-level options like the name and password.
On Vaelix you can change them visually in the sandbox settings manager, or edit the file directly. The manager is the safer choice if you would rather not touch Lua.
How do I change them without losing my edits?
Stop the server first. It rewrites its sandbox file on shutdown, so anything you edit while it is running gets overwritten.
Then change only the value after the equals sign and leave the key names, commas, and braces alone. Sandbox files are read at startup, so restart when you are done.
Tip: Defaults and key names changed between Build 41 and Build 42, and guides disagree on some of them. Read the comments in your own file before trusting any number, including the ones on this page.
What do the main sandbox settings do?
Zombie population: ZombieConfig.PopulationMultiplier (0 to 4) scales how many zombies exist, and the Zombie Count preset sets it for you. The normal preset is 0.65 in Build 42 and was 1.0 in Build 41, so never copy numbers between builds.
Respawn: RespawnHours is the in-game hours before zombies return to cleared areas, and 0 means they never do. RespawnUnseenHours is how long an area must go unseen first, and RespawnMultiplier is the share of peak population that comes back each cycle.
Day length: DayLength sets how many real-time minutes an in-game day lasts.
Loot: Loot is set per category, such as food, weapons, and ammo. Build 42 renamed and split many of the Build 41 settings (FoodLoot, WeaponLoot, and similar), so check the exact names in your own file. Food, medicine, and weapon scarcity shapes the first month more than most combat settings.
Why aren’t my changes applying to an existing world?
Many sandbox options are applied when the world is created or when new areas generate. New areas and new loot rolls pick up your changes. Areas players already explored and loot that already generated keep the old values, and settings like the start date are fixed at creation. Population shifts toward the new number gradually.
The save can also hold its own copy of the settings, in a map_sand.bin file inside the save folder. If edits seem to do nothing, that copy is the usual suspect, but back up the save before touching it.
Tip: Not sure what’s safe to change on a live world? Open a ticket and our team will help.
Frequently asked questions
Where are Project Zomboid sandbox settings stored?
In a Lua file named after your server, such as servertest_SandboxVars.lua, which is separate from the server.ini file. Stop the server before editing it.
How do I change the zombie population?
Use ZombieConfig.PopulationMultiplier, which runs from 0 to 4, or the Zombie Count preset. On an existing world the population moves toward the new number gradually.
How do I make zombies respawn in Project Zomboid?
Set RespawnHours to the number of in-game hours before zombies return to cleared areas. 0 means no respawn. RespawnUnseenHours and RespawnMultiplier fine-tune it, and defaults differ between Build 41 and Build 42.
Do sandbox changes apply to an existing world?
Partly. New areas and new loot rolls use the new values, but areas players already explored and loot that already generated keep the old ones. Settings like the start date are fixed when the world is created.