Project Zomboid Build 42 Multiplayer: Server Guide

Build 42 is the biggest update Project Zomboid has received, introducing the crafting overhaul, animal husbandry, basements, and a completely reworked meta-game. Running a multiplayer server on Build 42 requires understanding the new settings it introduces and how they affect performance with multiple players. This guide covers what changed and how to configure your server for the best experience.

What Build 42 changes for servers

Build 42 adds several systems that affect server performance and configuration:

• Animal system: Animals now roam the map, can be tamed and farmed. Each animal is a persistent entity the server tracks. More animals means more CPU load.
• Crafting overhaul: The new crafting system is more complex but runs server-side. Players crafting simultaneously generates more computation than the old system.
• Basements: Underground areas add a new map layer. Servers load and simulate basement chunks alongside surface chunks, increasing memory usage.
• Improved pathfinding: Zombies navigate more intelligently, which is both more immersive and more CPU-demanding.

System requirements for Build 42 servers

• CPU: Strong single-thread performance matters most. Project Zomboid's simulation is largely single-threaded. AMD Ryzen 9 7950X or equivalent recommended.
• RAM: Plan for 4 to 6 GB for a small server (4 to 8 players). For 16 or more players, budget 8 to 12 GB. Build 42's new systems add roughly 20 to 30 percent more memory usage compared to Build 41.
• Storage: SSD or NVMe strongly recommended. Map data is loaded and saved frequently, and Build 42's basement layer increases the volume of data.

Key sandbox settings for Build 42

Build 42 adds new sandbox options alongside the existing ones. Edit these in servertest_SandboxVars.lua (or through the server setup wizard):

Animal settings:

• AnimalSpawnRate: Controls how many animals exist in the world. Lower values reduce server load if you do not need the farming system.
• AnimalBreeding: Enables or disables animal breeding. Disabling it caps the animal population at the initial spawn count.

Zombie settings (updated):

• ZombieCount: Still the most impactful performance setting. Options range from Insane to None. For servers with 8 or more players, Normal or Low keeps performance stable.
• RearVulnerability: Zombies take more damage from behind. Enables more strategic combat without reducing zombie count.
• CognitionType: Navigate or Basic. Navigate uses the improved Build 42 pathfinding. Basic is less CPU-intensive but zombies are less threatening.

Loot and progression:

• LootRespawn: How often containers refill. Set to None for a hardcore experience, or Every Few Days for a more relaxed server.
• StarterKit: Gives new players basic supplies on first spawn. Reduces the frustration of dying immediately on a server where other players are already established.

Server performance tips

• Limit active cells: Each player loads a chunk of the map around them. More players spread across the map means more loaded cells. Encourage players to group up, especially early on.
• Scheduled restarts: Build 42 servers benefit from a restart every 6 to 12 hours. Memory usage climbs over time as more of the map is explored and modified.
• Trim inactive player data: Players who have not logged in for weeks still have safehouse data and character state saved. Periodically cleaning up inactive accounts frees resources.
• Use a whitelist: A whitelisted server avoids the overhead of random players joining and dying repeatedly, which creates zombie corpse entities and loot scattered across the map.

Connecting and managing players

Players connect by entering your server's IP and port (default 16261) in the multiplayer menu. The server admin account is set in servertest.ini with the AdminPassword field. Admins can use in-game commands to manage players, teleport, and adjust settings on the fly.

Important admin commands:

• /adduser "username" "password" to create accounts (when the server requires login).
• /setaccesslevel "username" admin to promote players.
• /teleport "username" to warp to a player.
• /servermsg "text" to broadcast a message to all connected players.