Join Project Zomboid Servers on Build 42.19 — Browser, Favorites, Invite & Fixes
Build 42.19 multiplayer joining guide: INTERNET and FAVORITES browser, Steam invites, Steam Relay, and direct connections on UDP 16261/16262.
Current status
Official multiplayer is available on the Build 42 Unstable client (MP test build). Use main menu MULTIPLAYER to join, or HOST for Steam co-op. You do not need to stay on Build 41 only for multiplayer, and you do not need Remote Play as a substitute for official MP.
Older “B42 has no multiplayer” guides are outdated
Early B42 builds shipped without multiplayer. On 42.19 the menu buttons are live. Long public seasons are still risky: Unstable updates can disrupt ongoing multiplayer worlds. Prefer whitelisted servers or Steam co-op for friend groups.
Quick-start: join a B42 server
- Confirm the client. Steam → Project Zomboid → Properties → Betas: use the branch your group agreed on (for current B42 multiplayer that is typically Unstable). On the main menu, note the version string in the corner — everyone must match the host/server version, not just “42.”
- Open MULTIPLAYER. Main menu → MULTIPLAYER.
- Browse INTERNET. Open the INTERNET public list. Use filters (name, empty/full, modded/vanilla, password, whitelist, different versions) to find a reachable host.
- Read the detail pane. Check Version, Players, Mods, and whitelist status before connecting. Prefer servers that list the same version you run.
- Set account fields. Enter Server Password if the host requires one. Choose an Account Username (seen by other players; also used in the save file name) and an Account Password that protects that username on the server — this is not your Steam password.
- JOIN SERVER. Wait for Workshop downloads if the host requires items. On first join you continue into character creation once the connection finishes.
Public list
INTERNET tab: good for discovering public worlds. Toggle filters for empty, full, modded, password-protected, and whitelist servers. Sorting by ping or player count helps, but a listed server can still be full, outdated, or offline by the time you click.
Account vs server password
Server Password is optional shared gate for everyone. Account Username / Account Password identify and protect your character slot on that server. Do not reuse real-world passwords.
Favorites & direct connect
Private hosts and friend-run dedicated servers often never appear on INTERNET. Use FAVORITES:
- Open FAVORITES → Add Server.
- Fill Favorite name (any label), IP/Domain, and Port.
- Default game ports on current servers are primary port 16261 (UDP) and secondary port 16262 (UDP). When the host only gives one number, they usually mean the primary port (16261 unless customized). If either value was changed, use the host’s exact pair — not a guessed range such as 16261–16271.
- Optional: Local IP for LAN entries when the host provides one.
- Save the favorite, select it, enter server/account credentials, set connection options, then JOIN SERVER.
Streamer / privacy note
The connect UI can show whether you are using a direct IP path or Steam Relay. Direct connection may expose your IP to the server administrator; Relay is intended to hide it. Use Streamer Mode if you need IPs hidden on screen while broadcasting.
Steam invite / HOST path
HOST (Steam co-op)
Main menu → HOST starts the in-game co-op host path. Create or load a server profile, set memory and options, then invite friends from the in-game INVITE FRIENDS screen once the host is running.
Accepting invites
Return to the main menu before accepting invites. Invites cannot be accepted while already in a game. The host must allow the join from the Invite Friends UI; a bare Steam friend request is not enough if the host never opened invite access.
- Everyone on the invite must share the same Steam branch and the same Unstable version.
- A non-Steam (
-nosteam) client cannot join a Steam server, and a Steam invite will not work the other way either. - For the MP test build, prefer whitelisted servers or Steam co-op over long open public seasons.
Version, branch, and mods must match
| Check | What “match” means | Typical symptom |
|---|---|---|
| Steam branch | Unstable vs none (stable/legacy) must be the same for the whole group | Hard refuse / version error before load |
| Build version | Same 42.x patch (for example all on 42.19 after the same update) | Server version (…) does not match the client (…) |
| Workshop items | Server Workshop list; clients subscribe/download the same items | Workshop version different / download errors |
| Mod enable list | Mod IDs and order expected by the host | Checksum / mod rejection after Workshop OK |
| Maps | Map packs listed by the server must be present for clients | Join stalls or world load failure |
When the join UI says the server requires Workshop items, allow the automatic download first. If an item fails, note the ID, open Steam Workshop, subscribe or re-subscribe to force an update, then retry. A server that was not restarted after a Workshop change can still reject clients with a version-mismatch style Workshop error until the host restarts.
Steam Relay vs direct UDP (16261 / 16262)
On the connect / Add Server UI, open Connection Options and locate Use Steam Relay:
- Direct path: client tries UDP to the host’s ports. Hosts (or their VPS firewall) need inbound UDP on the primary port (default 16261) and the secondary UDP port (default 16262). If either port was customized, forward those exact values.
- Steam Relay: useful when the host is behind strict NAT or did not port-forward. Try on, then off, keeping everything else identical so you know which path works.
- Older guides that mention
DisableSteamRelayor a fixedSteamPort=8766line are outdated for current builds. Use the in-game Relay toggle and the host’s published ports instead. - UPnP on the host may auto-map ports; if UPnP fails, the server falls back and players may need Relay or manual forwards. Details for hosts: server administrator tips and B42 hosting guide.
Stuck on “Getting Server Info…”?
That screen means the client is still querying mods, version, and network path. Do not delete your whole
Zomboid folder as a first step. Follow the log-driven flow in Getting Server Info troubleshooting.
Common join failures
| What you see | What to do first |
|---|---|
| Server version does not match the client | Align Steam branch and patch; host restarts after updating. B41 clients cannot join B42 hosts. |
| Workshop item version different / download error | Resubscribe the listed items; host restarts after Workshop updates; remove abandoned map/mod packs. |
| Connection failed / server failed to respond | Confirm the host is still online; toggle Use Steam Relay; check the two UDP ports or use Relay; check OS firewalls for Project Zomboid. |
| P2P session connect fail | Retry Relay on/off; host checks NAT/firewall; try a different network (mobile hotspot) once to isolate local UDP blocks. |
| Wrong server password / whitelist lockout | Confirm the shared server password; if the server is closed (not open to public accounts), an admin must create your account first — see whitelist guide. |
| Unknown account / username errors | Use the account username the server expects; do not confuse it with Steam display name. See unknown account guide. |
| Vague “code” popups | Read console.txt keywords instead of chasing unofficial error-code myths — multiplayer log guide. |
Client log location is typically under your user Zomboid folder (console.txt and Logs/). Redact passwords and tokens before sharing logs.
Build 41 as a legacy branch
Build 41 remains useful for long public servers, older mod catalogs, and groups that want fewer Unstable wipes. It is a legacy multiplayer ecosystem, not the only multiplayer option.
| Need | Prefer Build 41 | Prefer Build 42.19 Unstable MP test |
|---|---|---|
| Long public server, rare wipes | Yes | No — patches disrupt MP worlds |
| B42 systems (animals, crafting, combat, map changes) with friends | No | Yes |
| Largest older mod catalog | Usually | Only mods updated for current 42.x |
| Small friend group OK with resets | Optional | Best fit: Steam co-op or whitelist |
- To run legacy B41 again: Steam → Properties → Betas → opt out of Unstable / select the branch your B41 server documents, then wait for the redownload.
- Switching branches rewrites the install; back up single-player and hosted saves you care about before swapping.
- Dual folders or
-nosteamcopies are optional power-user setups, not required for normal play. A non-Steam client still cannot join Steam-authenticated servers. - Do not treat Remote Play Together / split-screen streaming as the primary multiplayer solution for B42 anymore — official MULTIPLAYER and HOST paths exist on 42.19.
Checklist
- Same Steam branch and same version on every client and the host.
- Main menu → MULTIPLAYER → INTERNET or FAVORITES (Add Server with correct IP + port).
- Set Server Password (if any) plus Account Username / Account Password.
- Match Workshop items and mod/map lists; let auto-download finish.
- If direct join fails, toggle Use Steam Relay; hosts open UDP 16261 and 16262 (or their custom pair).
- For friends only: HOST + in-game Invite Friends, or a whitelisted dedicated server.
- Treat Unstable multiplayer progress as expendable; back up before every game update.
Practical limits
Build 42 multiplayer is still an Unstable test path: expect desync, forced wipes, and patch churn. Back up worlds you care about. Live public-server population counts and third-party host panels are outside this page’s scope — use Steam and the in-game browser for current listings.
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