Multiplayer Guide: Host, Dedicated Server & Blueprints

Multiplayer in Factorio lets multiple people play the same factory world together, either on a local network or over the Internet. Proper multiplayer setup and coordination (mods, versions, blueprints, server visibility and networking) are essential for a smooth, stable experience.

Basic multiplayer modes

• Host (listen) game: a player starts a game from the main menu -> Multiplayer. That player becomes the host and others connect to their IP and port.
• Dedicated server: run a headless server build on a machine (recommended for persistent worlds and public servers). The headless build omits client assets and is suitable for hosting.
• Join methods: Internet lobby, LAN lobby, direct IP/port, or using Steam game invites. The Internet lobby will list servers set to be visible on the public list.

Versions, mods and compatibility

• All players and the server must run the exact same game version and have identical mod installations. Mismatches prevent connecting.
• Scenarios behave differently from standard saves: they do not require clients to install scenario scripts, allowing some server-side control without client mods.

Server visibility and connection details

• Default network port: UDP 34197. The server and clients use UDP only. Ensure that routers, firewalls, and antivirus allow UDP through this port (or change the port in server config).
• NAT/port forwarding: a server behind NAT needs port forwarding for other players to connect. If forwarding is not possible, use VPN/virtual LAN tools (e.g., Hamachi) or host on a machine with a public IP.
• The game implements its own reliable layer over UDP; routers that modify or randomize the source port can break connectivity. Avoid routers that apply static port randomization for UDP traffic to the server port.
• DNS SRV records: Factorio supports DNS SRV for the _factorio._udp service name so you can publish a hostname that directs clients to a specific port without requiring them to enter the port.

Practical server setup (headless server)

• Use the headless server build for dedicated servers where possible; it reduces unnecessary dependencies and resource use.
• Typical install pattern: extract the server into a chosen directory (e.g., /opt/factorio), create a dedicated system user to run the server, and start the binary with the --start-server or --create options to manage saves.
• Ensure correct file ownership and that the saves directory exists. If the server logs complaints about missing save files, the executable is likely installed correctly.

Player limits and performance

• The theoretical player limit is very large (reported limits far above typical use), but practical limits are much lower; servers commonly host dozens of players without issue, but performance depends on server hardware, world size, and UPS.
• Console versions (e.g., Nintendo Switch) support cross-platform multiplayer up to 64 players.

Game rules that affect multiplayer

• Research: by default, research is per force (team). If multiple forces exist, each force has an independent tech tree and research progress; within a force, only one technology can be actively researched at a time.
• Achievements: achievements are enabled only in freeplay; scenarios and custom save settings or use of cheats and console commands disable achievements. In multiplayer, a player must spend at least 50% of playtime in a save to earn achievements on that save.

Coordination tools for multiplayer play

• Shared blueprints: use the in-game Blueprint library’s left-hand "Shared blueprints" pane to place designs that all connected players can access. Drag blueprints or blueprint books from your personal library into Shared blueprints for easy team-wide use.
• Export/Import strings: use "Export to string" to produce a text string for a blueprint or blueprint book and send it to teammates outside the game (chat, Discord). Recipients use "Import string" to restore the blueprint into their library; this works across different saves and servers.
• Blueprint books: organize stations, defense layouts, starter bases, and train intersections into books. Shared blueprint books let the team pick and switch designs in-place (active blueprint switching can be done with Shift + mouse wheel).

Player identity and controls

• Player vs character: the term "player" refers to the controlling entity (including optional god mode) while the "character" is the in-world avatar. Players can customize character color for easier identification in multiplayer.
• Replays: multiplayer replays allow switching the camera focus between players during playback for reviewing events from different perspectives.

Tips and common pitfalls

• Always verify version and mod parity before joining to avoid failed connections.
• If players experience issues connecting from the Internet, check UDP port forwarding, firewall rules, and router behavior regarding UDP port randomization.
• Prefer a dedicated headless server for long-running, public, or large-player-count games to reduce client-host latency and improve stability.
• Use shared blueprints and exported blueprint strings to reduce confusion and ensure consistent station/defense/train designs across the team.
• When hosting on consumer routers, confirm that the router does not alter UDP source ports and that the server port is forwarded to the hosting machine’s correct local IP.

This covers the practical essentials for running, joining, and coordinating multiplayer games in Factorio.