The original Left 4 Dead has three game modes. You pick the mode and the campaign on the deploy form, and the map pool changes to match the mode you chose. Every original campaign ships with the server, so nobody has to download anything to play. Here is what each mode is and which campaigns it runs.
Co-op
The core mode. Four survivors fight through a campaign against the AI-driven horde. Empty survivor slots are filled by AI teammates, so a smaller group can still play. Co-op runs on all six original campaigns.
- No Mercy: map id l4d_hospital01_apartment, the default campaign.
- Crash Course: map id l4d_garage01_alleys, the short bridge campaign.
- Death Toll: map id l4d_smalltown01_caves.
- Dead Air: map id l4d_airport01_greenhouse.
- Blood Harvest: map id l4d_farm01_hilltop.
- The Sacrifice: map id l4d_river01_docks.
Versus
4v4. One team plays the survivors while the other team plays the Special Infected, then you swap. Valve only shipped Versus maps for four campaigns, so Crash Course and The Sacrifice are Co-op only.
- No Mercy: map id l4d_vs_hospital01_apartment.
- Death Toll: map id l4d_vs_smalltown01_caves.
- Dead Air: map id l4d_vs_airport01_greenhouse.
- Blood Harvest: map id l4d_vs_farm01_hilltop.
Survival
Hold one spot against endless waves and see how long you last. The original Left 4 Dead ships one dedicated Survival map.
- Lighthouse: map id l4d_sv_lighthouse.
Player counts
The engine caps a server at 8 players. Co-op is four survivors. Versus is 4v4, which uses all eight slots. Pick a Small (4p) or Medium (8p) size on the deploy form to match the mode you want.
Deploy a Left 4 Dead server by the hour