Two things break a Project Zomboid dedicated server more than anything else: it doesn’t show up for anyone, or everyone hangs forever on “Loading World.” I’ve hit both. Here’s the order to check things in, fastest fix first.
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“Server not responding” or nobody can see it
1. Ports — this is it 80% of the time
Project Zomboid needs UDP ports open, and people routinely forward only one of them. The defaults:
- 16261 UDP — the main server port
- 16262 UDP — direct player connections
- 8766 UDP and 8767 UDP — Steam query ports, needed for the server browser to see you
Confirm your actual values in your server ini rather than trusting the defaults — if you changed DefaultPort or SteamPort1/SteamPort2, forward what’s really set. Forward them as UDP, not TCP. That’s the mistake that eats an entire evening: TCP rules look correct in the router UI and do nothing.
If you can connect from inside your own network but nobody outside can, it’s ports. Every time.
2. Firewall on the server itself
Router forwarding is only half of it. If you’re on a Linux box with ufw active, the packets die at the OS:
sudo ufw allow 16261/udp
sudo ufw allow 16262/udp
sudo ufw allow 8766/udp
sudo ufw allow 8767/udp
sudo ufw status3. Steam browser vs direct connect
If direct connect by IP works but the server never appears in the public list, that’s the Steam query ports (8766/8767) — not your game port. The server is running fine; Steam just can’t advertise it.
Test direct connect first to isolate which problem you actually have. It saves you from “fixing” a server that was never broken.
4. You’re giving people the wrong IP
Obvious, still common. Players outside your network need your public IP, not the 192.168.x.x one. And if your ISP hands you a dynamic IP, it changed at some point and the address you posted in Discord is dead.
Stuck on “Loading World” forever
This one is almost always mods.
1. Mod list mismatch
Your server ini has two separate lines that both have to be right:
WorkshopItems=2169435993;2200148440
Mods=modnamehere;anothermodnameWorkshopItems takes the numeric Workshop IDs. Mods takes the internal mod folder names. They are not the same values, and filling in one but not the other produces exactly this symptom — the client connects, starts loading, and never finishes.
Order matters too. Mods with dependencies have to load after what they depend on. If a mod page says it requires another mod, put the requirement first.
Clients also have to be subscribed to the same mods. One player missing one mod means that player hangs while everyone else is fine.
2. Not enough RAM
A vanilla server is light. A heavily modded server is not, and the default heap is too small for a big mod list. In ProjectZomboid64.json, raise the max heap:
"-Xmx4g"Give it 4GB as a starting point for a modded server, more if your list is long. If it loads vanilla but hangs with mods on, this is a strong suspect — and if the process is being killed outright, you’re out of memory at the OS level.
3. Build mismatch
Build 41 and Build 42 servers will not accept clients from the other branch. If the server updated and your players didn’t, or vice versa, nobody gets in. Check that everyone is on the same branch in Steam’s beta settings.
4. Corrupted save
If it worked yesterday, you changed nothing, and it hangs today — back up your save folder and try a fresh world. If the fresh world loads instantly, the save is the problem, and you’ll want that backup.
Quick triage order
- Can you connect locally? If no, the server isn’t running — check the console output, not the network.
- Can you direct-connect by public IP? If no → ports/firewall.
- Direct works but not in the browser? → Steam query ports.
- Connects but hangs loading? → mods, then RAM, then build version.
- Worked before, changed nothing? → save corruption or an update.
When it’s not your fault
Sometimes you’ve done everything right and the box itself is the problem. Shared game hosting is where this gets maddening — you often can’t see real logs, can’t edit config files directly, can’t control which build you’re on, and can’t open a port without a support ticket. You end up troubleshooting someone else’s platform instead of your server.
That’s the reason I run mine on a VPS with root access. When something breaks I can read the actual console output, edit the ini myself, and open a port in ten seconds. I use EVLBOX for this — small team, active on Discord, and they’ve sorted my problems same-day.
👉 EVLBOX VPS (affiliate link) — use TOOBROKE20 for 20% off.
If you’d rather compare managed options first, I went through those in best Project Zomboid server hosting.