How to play Doom co-op online in 2026
How to play Doom co-op online in 2026
Set up Doom co-op online in 15 minutes.
Doom co-op is alive and well in 2026. You won’t find it on Steam matchmaking — the classic Doom community lives in dedicated source ports and a small handful of server browsers. This guide gets you from “I own Doom on Steam” to “I am playing co-op with a friend on a custom megawad” without the trial and error.
Before you start
- A legal copy of Doom or Doom II (Steam, GOG, the KEX re-release, or original CDs).
- A friend who wants to play co-op (or willingness to join a public server).
- A reasonably stable internet connection — Doom is light, but lag still matters.
You will need
- Zandronum (recommended for online multiplayer).
- Doomseeker (the de-facto server browser for Zandronum).
Steps
Step 1 · Install Zandronum
Go to zandronum.com/download and grab the latest Windows/Mac/Linux build. Zandronum is the source port that owns the modern Doom multiplayer scene — better netcode than GZDoom for online play.
Step 2 · Drop your IWAD into Zandronum's folder
Copy
doom.wad,doom2.wad, orfreedoom2.wadinto the Zandronum install folder. Zandronum needs it there to launch.Step 3 · Install Doomseeker
Grab Doomseeker from doomseeker.drdteam.org. Point it at your Zandronum executable in Tools → Configuration → Engines.
Step 4 · Find a co-op server
Open Doomseeker, refresh the server list, filter by game mode = Cooperative. Sort by ping. Double-click a server you like — Doomseeker auto-launches Zandronum into it.
Step 5 · Host with a friend (instead)
If you want a private game: in Zandronum, choose Multiplayer → Host Game, pick the WAD you want to play, set game mode = Cooperative, set max players. Then port-forward UDP 10666 on your router (or use Hamachi/ZeroTier for a no-port-forward LAN). Share your public IP with your friend; they join via Doomseeker’s Custom Server menu.
Frequently asked questions
Why Zandronum and not GZDoom?
GZDoom has great single-player and modding support, but its netcode for online play is rough. Zandronum forked from GZDoom years ago to fix exactly this — it prioritises stable multiplayer and has the active server scene.
Can I play with someone on the KEX re-release of Doom?
Not directly. The KEX re-release uses its own matchmaking and is its own ecosystem. To play with the classic-Doom community you both need Zandronum (or Odamex/ZDaemon for deathmatch).
What's the difference between Zandronum, Odamex and ZDaemon?
All three are multiplayer-focused source ports. Zandronum is the most populated and has the best mod support. Odamex focuses on vanilla-accurate deathmatch. ZDaemon is older, still has competitive deathmatch leagues.