Multiplayer & Servers
Scrap Mechanic supports online co-op multiplayer, letting you build, explore, and survive with friends. From casual 2-player sessions to dedicated servers with dozens of players, this guide covers connection methods, server setup, configuration, optimization, and troubleshooting.
Online Connection Methods Comparison
| Method | Players | Setup | Uptime | Best For |
|---|---|---|---|---|
| Host & Join (P2P) | 2-8 | Easy | Only when host is online | Casual play with friends |
| Dedicated Server | 8-32+ | Medium-Hard | 24/7 (if running) | Persistent worlds, communities |
| Community Server | Varies | None (just join) | 24/7 | Playing with strangers, modded servers |
| LAN | 2-8 | Easy | Only when host is online | Local network play |
Dedicated Server Setup
A dedicated server runs independently of any player's game, allowing 24/7 uptime and persistent worlds. Here's how to set one up.
System Requirements
- OS — Windows 10/11 or Linux (via Wine/Proton)
- CPU — Multi-core processor (more cores = more players supported)
- RAM — 8GB minimum (16GB+ recommended for 10+ players)
- Storage — SSD recommended (faster world loading, less lag)
- Network — Stable broadband with good upload speed (10+ Mbps upload for 10+ players)
- Steam — SteamCMD for server installation (no full Steam client needed)
Installation Steps (Windows)
- Install SteamCMD — Download from Valve's developer site, extract to a folder
- Download server files — Run SteamCMD with the Scrap Mechanic dedicated server app ID
- Open command prompt in the SteamCMD folder
- Run:
steamcmd +login anonymous +force_install_dir C:\SM_Server +app_update [APPID] validate +quit - Replace [APPID] with the Scrap Mechanic dedicated server app ID (check SteamDB for current ID)
- Configure server — Edit the server config file (see below)
- Port forwarding — Forward the game port (default 25000 UDP) on your router
- Start server — Run the server executable or batch file
- Test connection — Launch the game, connect to your server's IP or localhost
Installation Steps (Linux)
- Install SteamCMD via your package manager or manual download
- Use Wine or Proton to run the Windows server executable (native Linux server may not be available)
- Follow the same configuration and port forwarding steps as Windows
- Consider using a VPS (Virtual Private Server) for 24/7 uptime
Configuration Parameters Explained
Server settings are stored in a configuration file (usually JSON or XML format in the server directory).
| Parameter | Default | Description |
|---|---|---|
serverName | "Scrap Mechanic Server" | Server name shown in browser |
maxPlayers | 8 | Maximum concurrent players |
port | 25000 | UDP port for game traffic |
password | "" (none) | Server password (leave empty for public) |
gameMode | "survival" | Game mode (survival, creative, challenge) |
difficulty | "normal" | Difficulty level (easy, normal, hard) |
worldSeed | Random | World generation seed (for specific maps) |
enablePvP | false | Allow player vs player damage |
enableCheats | false | Allow console commands for all players |
autoSaveInterval | 300 (5 min) | Auto-save interval in seconds |
dayNightCycle | true | Enable day-night cycle |
raidEnabled | true | Enable farm raid events |
adminList | [] | List of admin player IDs/Steam IDs |
whitelist | [] | List of allowed players (empty = public) |
modList | [] | List of enabled mods (all players need same mods) |
Player Count Performance Optimization
More players = more strain on the server. Optimize for your player count with these tips:
Small Servers (2-8 players)
- Standard settings work fine
- Host & Join (P2P) is usually sufficient
- No special optimization needed
- Can use mods without major performance impact
Medium Servers (8-16 players)
- Use a dedicated server (P2P will lag)
- Reduce entity density — limit complex creations and automated systems
- Increase auto-save interval to reduce lag spikes
- Limit mod count to essential mods only
- Use SSD for server storage
- Ensure 16GB+ RAM
Large Servers (16-32+ players)
- Powerful dedicated hardware required (multi-core CPU, 32GB+ RAM)
- Strict limits on complex creations (vehicles, automated farms)
- Regular world cleanup to remove abandoned creations
- Minimal mods (visual mods only; avoid gameplay mods that add entities)
- Consider splitting into multiple smaller servers
- Use a VPS or dedicated server hosting service
- Network bandwidth: 50+ Mbps upload recommended
General Optimization Tips
- Limit physics objects — Too many moving parts (pistons, wheels, bearings) cause server lag
- Use static blocks — Welded/bolted creations are less CPU-intensive than dynamic ones
- Reduce automation — Limit the number of active sensors, controllers, and vacuum pumps
- Regular restarts — Restart the server every 12-24 hours to clear memory leaks
- Backup regularly — Auto-backup the world file in case of corruption
- Monitor performance — Use server console or tools to track CPU, RAM, and tick rate
Collaboration Roles
In multiplayer, dividing roles makes the group more efficient. Here are common roles for a Survival team:
| Role | Responsibilities | Focus Skills |
|---|---|---|
| Builder / Engineer | Base construction, vehicle building, automation systems | Building, logic circuits, pistons |
| Farmer | Crop management, food production, packing for sale | Farming, irrigation, cooking |
| Miner / Gatherer | Resource gathering, mining, exploration | Mining, drilling, map knowledge |
| Fighter / Defender | Combat, base defense, Warehouse runs | Weapons, bot tactics, turret setup |
| Technician | Vehicle maintenance, fuel management, power systems | Engines, fuel, generators, repairs |
| Explorer / Scout | Map exploration, locating Warehouses, finding ruins | Navigation, vehicle operation, risk assessment |
Roles aren't rigid — players can switch or share responsibilities. The key is communication and coordination.
Permission Protection
Protect your world and creations with these permission and security settings:
- Admin system — Grant admin privileges to trusted players; admins can use commands, kick/ban, and modify settings
- Whitelist — Only allow specific players to join (ideal for private servers with friends)
- Password protection — Require a password to join (simple but effective)
- Build protection — Some server mods allow protecting specific areas from modification
- Rollback — Use server backups to roll back griefing or accidental destruction
- Logging — Enable server logging to track player actions (who built/destroyed what)
- Kick/Ban — Admins can kick disruptive players or ban them permanently
- PvP toggle — Disable PvP to prevent friendly fire and griefing via combat
Common Troubleshooting
| Problem | Cause | Solution |
|---|---|---|
| Can't connect to server | Wrong IP, port not forwarded, firewall blocking | Verify IP, forward port, check firewall/antivirus |
| Connection timeout | Server offline, network issue, too many players | Check server status, test connection, reduce player count |
| Version mismatch | Game or mod version differs from server | Update game, install same mods as server |
| High latency / lag | Slow network, server overloaded, too many entities | Use wired connection, optimize server, reduce creations |
| Rubber-banding | Server tick rate drops, network instability | Reduce server load, check network, restart server |
| Crashes on join | Mod conflict, corrupt world, missing assets | Verify mods match, restore world backup, validate files |
| Can't see server in browser | Server not registered, port issue, Steam down | Direct connect via IP, check port forwarding, check Steam status |
| Inventory/creation lost | Server crash during save, desync | Restore from backup, re-sync with server |
| Voice chat not working | Mic permissions, in-game settings, network | Check mic permissions, verify in-game audio settings, use external voice (Discord) |
Multiplayer Tips
- Communicate — Use in-game chat or voice (Discord recommended) to coordinate with your team
- Share resources — Pool materials in a shared storage for the team's benefit
- Coordinate building — Plan base layout together to avoid conflicting constructions
- Set spawn points — All players should set their spawn at the base bed
- Divide and conquer — Split tasks (one farms, one mines, one builds) for faster progression
- Backup the world — Server hosts should regularly back up the world file
- Use the same mods — Ensure all players have identical mod sets to avoid crashes
- Respect other players — Don't destroy others' creations, don't steal resources, play cooperatively
- Save before quitting — If you're the host, make sure the world saves before closing the game
- Have fun — Scrap Mechanic is best enjoyed with friends; experiment, build crazy things, and enjoy the chaos
Related Guides
- Mods Guide — Set up modded multiplayer servers
- Blueprints & Schematics — Share and use blueprints in multiplayer
- Console Commands & Dev Mode — Admin commands and server management
- Base Building Guide — Build a base for your whole team