Do Zombies Respawn in Project Zomboid? Server Settings

Do zombies respawn in Project Zomboid? Only if the world's sandbox settings allow it, and in Build 42 the default answer is increasingly no. The Apocalypse preset, which Build 42 treats as the canonical game mode, has zombie respawn switched off. Rising, Extinction and Six Months Later still refill cleared areas. On a server, one number decides it: RespawnHours in the server's SandboxVars file. At 0, cleared areas stay cleared.

This page covers the four settings behind zombie respawn, what each game-mode preset sets them to, and how to change them on your server. Every key, range and default comes from the dedicated server's own files on the public branch, Build 42.20 (42.20.4), checked on 27 September 2026.

The four settings that control zombie respawn

They sit in the ZombieConfig block of the sandbox file. The descriptions in quotes are the game's own help text.

Read together, the code defaults mean: every 72 hours, a cell may get back up to 10% of the population it is meant to have, but only in chunks nobody has looked at for 16 hours. That is why zombies seem to "come back" to a town you left alone, and never appear in front of you.

RedistributeHours is not respawn. It moves zombies that already exist into emptied parts of the same cell. A cleared street can fill up again with respawn switched off, because the neighbours walked in. To keep an area truly empty, you need RespawnHours = 0.0 and a longer (or zero) RedistributeHours.

What each game mode sets

The code defaults above are not what most worlds use, because every game mode preset overrides them. From the preset files shipped with 42.20:

Apocalypse lost its respawn in Build 42.15, when The Indie Stone rebalanced the game modes and described Apocalypse as the "Lore Canon" mode with "core changes including removing Zombie Respawn". In Build 41, Apocalypse used 72 / 16 / 0.1 and did respawn zombies. If your group moved over from Build 41, this is the change you are noticing.

A new Build 42 server probably starts with respawn off

The game's default sandbox file loads the Apocalypse preset, and a dedicated server that finds no sandbox file writes one from the values loaded at boot. So a server first started on 42.20 should come up with RespawnHours = 0.0. Don't assume: open the file described below and check the actual value on your server.

The "Zombie Respawn" dropdown

Sandbox files also carry a top-level ZombieRespawn value (1 High, 2 Normal, 3 Low, 4 None), and the presets set it to match: Apocalypse and Outbreak use 4, Rising 3, Extinction 2. As far as we can tell from the 42.20 server code, nothing reads that value: the respawn logic runs off the ZombieConfig numbers above. The Indie Stone hasn't documented this, so don't rely on the dropdown alone. Change the numbers.

Where the setting lives on your server

Project Zomboid names its config files after the server name it is started with. On a GSK server, the server is started with -cachedir=/home/container/.cache and the name from the Server Name startup variable, so the file is:

.cache/Server/<Server Name>_SandboxVars.lua

Find the name on the panel's Startup tab. The egg's default is Pterodactyl, which gives .cache/Server/Pterodactyl_SandboxVars.lua. If you change the Server Name, the server looks for a file under the new name and generates a fresh one, so your settings seem to reset. Project Zomboid server settings and config files covers that and the other three config files.

Inside, the respawn settings are in the ZombieConfig block:

    ZombieConfig = {
        PopulationMultiplier = 0.65,
        PopulationStartMultiplier = 1.0,
        PopulationPeakMultiplier = 1.5,
        PopulationPeakDay = 28,
        RespawnHours = 0.0,
        RespawnUnseenHours = 0.0,
        RespawnMultiplier = 0.0,
        RedistributeHours = 12.0,
        -- more settings follow
    },

How to turn zombie respawn on or off

There are two ways. Both end with the new values saved in the file.

Option 1: the in-game admin panel (no restart)

1. Join the server with an admin account. Project Zomboid admin commands covers getting admin.
2. Click the round ADMIN button on the left edge of the screen, then Sandbox Options.
3. Find Respawn Hours, Respawn Unseen Hours, Respawn Multiplier and Redistribute Hours, and set them.
4. Click Apply.

The server applies the new values to the running world and writes them to <Server Name>_SandboxVars.lua in the same step, so they survive a restart. This is the safer route, because the panel can't produce a syntax error.

Apply Preset changes everything, not just respawn

The same window has a preset list (Apocalypse, Outbreak, Extinction, Rising, Six Months Later) and an Apply Preset button. A preset overwrites every sandbox setting, including loot, day length and zombie behaviour. To change only respawn, edit the four fields by hand.

Option 2: edit the file

1. Stop the server. The file is only read at boot, and a running server can overwrite it from the admin panel.
2. Open Files, go to .cache/Server/, and open <Server Name>_SandboxVars.lua.
3. Change the values in ZombieConfig, keeping every comma.
4. Save and Start the server.

A typo stops the server from starting

The sandbox file is Lua code. If the server can't read it at boot, it quits rather than falling back to defaults. Download a copy before you edit, or take a backup first (How to create a backup).

Values to copy

The last two rows only change how fast a cell is topped back up to its target population. How many zombies a cell is meant to hold is set by the population settings next to them (PopulationMultiplier and the start and peak values), so raising RespawnMultiplier on a low-population world still gives you a low-population world.

Zombies vanishing is a different problem

If zombies are disappearing rather than failing to come back (a horde is gone when you return to an area a minute later), that is a known Build 42 bug rather than a setting. The Indie Stone described it in the 42.21 notes as "an issue in which zombies would disappear after a player left and re-entered a 'chunk' of the game world" and says it "has now been fixed in both SP and MP".

As of 27 September 2026, 42.21 is on the unstable branch only. The stable branch your server runs by default does not have the fix yet. Moving a server to unstable means every player has to switch branch too, so for most servers the answer is to wait for 42.21 to reach stable. Project Zomboid multiplayer explains how branch mismatches break joins.

FAQ

Do zombies respawn in Project Zomboid?

Only when RespawnHours is above 0. In Build 42 the Apocalypse and Outbreak presets set it to 0, so no zombies respawn. Rising, Extinction and Six Months Later set it to 72, so cleared areas slowly refill.

Do zombies respawn in cleared areas I am standing in?

No. Respawn only happens in chunks that nobody has seen for RespawnUnseenHours, which is 16 hours in every preset that respawns at all.

Why are there zombies in an area I cleared if respawn is off?

Migration. RedistributeHours moves existing zombies into empty parts of the same cell, and zombies also follow sounds. Set RedistributeHours = 0.0 to stop the in-cell migration.

Is it ZombieRespawn or RespawnHours?

RespawnHours, and the other ZombieConfig values. In 42.20 the top-level ZombieRespawn value is not read by the game code.

Do I need to restart the server after changing respawn settings?

Not if you use Sandbox Options in the admin panel and click Apply. If you edit the file directly, stop the server first and start it afterwards, because the file is only read at boot.

What to read next

• Project Zomboid server settings and config files: the INI, the sandbox file and spawn files
• Project Zomboid admin commands: admin access, roles and the admin panel

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