Revision History

v1.0: October 2026 — Initial version

Introduction

MODs are to be installed and managed by customers themselves. We do not verify the operation of individual MODs or provide installation services, so we cannot guarantee operation with MODs installed.

This article summarizes points that customers can check themselves regarding common issues with MOD servers: "lag/freezing" and "disconnection immediately after joining".

Our servers are initially configured with the latest stable version (Build 42). You can also switch to Build 41 (see "How to Play Build 41 on Project Zomboid Servers").

How to Install Mods (Review)

Press Stop in the Console tab and wait for it to stop.
Open Zomboid/Server/ProjectZomboid.ini in the Files tab (if you have changed the save name, it will be the .ini with that name).
Write the IDs in WorkshopItems= and Mods=. If there are multiple IDs, separate them with ; (semicolons). For additional maps, also write them in the Map= line according to the instructions on that mod's page.
Save and start with Start.

Mods line and Map line in the configuration file — Write the mods to load in Mods= and maps in Map=

WorkshopItems line in the configuration file and the description above it — List the workshop IDs to acquire in WorkshopItems=, separated by semicolons

WorkshopItems= is the ID for acquiring, and Mods= is the ID for loading—these are different numbers. The explanation in the configuration file also states this. Please check the IDs on each mod's workshop page.

The first startup after adding mods takes time for acquisition. If there are many mods, it may take about 10 minutes. Please wait until *** SERVER STARTED **** appears in the console. From the second startup onward, it only needs to check if they are already acquired.

The game panel does not overwrite these 3 lines. Even after restarting, the content you wrote will remain as is.

Also Be Mindful of Disk Space

Mod files use disk space. The game itself is about 7GB, and adding many mods can add around 10GB on top of that. Please check your disk usage at the top of the game panel screen.

Checklist to Prevent Lag and Disconnections

First, verify you can play without MODs

Before installing MODs, verify that everyone can join and play normally without any MODs. By confirming this first, you can isolate whether issues that occur later are caused by MODs.

Add MODs gradually and verify each time

If you install many at once, you won't know which one is the cause. Add a few at a time, verify that you can join and that performance doesn't degrade, then proceed to the next.

Use MODs compatible with Build 42

Our servers are initially configured with the latest stable version (Build 42). Check the MOD's Workshop page to verify it is compatible with Build 42. Incompatible MODs will leave errors in the server logs (see "Verify in server logs" below).

If you have switched to Build 41, please select MODs compatible with Build 41. For instructions on switching versions, see "How to play Build 41 on a Project Zomboid server".

Match players' MODs with the server

If the MODs on the server and players don't match, players will be disconnected shortly after joining with the following message:

You were kicked because your game files do not match the server's.

When joining, if the "Server WORKSHOP Items" screen appears ("The following Steam WORKSHOP items are required to join this server:"), acquire the displayed MODs before joining.
MODs you have manually modified or MODs with the same name obtained from outside the Workshop can cause mismatches.
When a MOD is updated on the Workshop, restart the server. The server verifies MOD status each time it starts. Players should also restart their game before joining.

If you see "Server version (…) does not match client version (…)", the game version is mismatched, not the MODs. The version numbers appear in the parentheses. For a solution, see "How to play Build 41 on a Project Zomboid server".

Additional maps and large cities tend to be heavy

Installing many additional maps or setting large cities like Louisville as the spawn point tends to make loading immediately after joining heavy and increases join time itself. If you experience heaviness, first review the number of additional maps and spawn points.

Keep memory headroom

The more MODs you use, the more memory the server consumes. If you plan to use many MODs, please consider a plan with ample memory.

Check the Server Logs

Open Zomboid/Logs/ in the Files tab.
Open the most recent DebugLog-server.txt with a date and time stamp (you may download it and open it locally if you prefer).
Search for the following text.

File screen showing dated logs in the Zomboid/Logs folder — Inside Zomboid/Logs. Open the DebugLog-server.txt with a date and time stamp

Search Text	Meaning	Action
`checksums do not match`	The MODs do not match between the joining player and the server	See "Match the Joining Player's MODs with the Server" above
`doesn't exist` / `FileNotFoundException`	There is a MOD that is not compatible with the current version	See "Use MODs Compatible with Build 42" above. Remove that MOD or replace it with a compatible version

The FileNotFoundException line shows the folder for that MOD. The number following steamapps/workshop/content/108600/ is the Workshop ID for that MOD. You can identify which MOD it is from this.

The logs will contain many other lines, but please check these two first.

When Removing or Replacing MODs

First, stop the server using Stop in the Console tab, then take a backup in the Backup tab before proceeding.
Game panel backups do not include the MOD files themselves (though the MOD lines in configuration files are included). The MODs will be retrieved again on the first startup after restoration.

For restoration procedures, see "Restoring from a Backup".

If It's Still Slow

Please contact us via a support ticket. In doing so, it would be helpful if you could include the date and time when the slowdown occurred and the number of people connected at that time. We will review the server-side records (processing delays, connections, disconnections).