Fallout 4 multiplayer, built from the ground up.
Connect to a dedicated server and share the Commonwealth with other players. Version 1.1.0 adds invite-based internet hosting through Iroh, a full graphical host workflow, stronger controller support, and optional public server discovery alongside the existing player sync and shared world state.
Overview
Shared-world Fallout, one system at a time
Commonwealth Online is a multiplayer framework for Fallout 4, supporting both the Anniversary Edition and the original release. Multiple players connect to a dedicated server and share the Commonwealth while each client continues to run its own copy of the game. The framework synchronises movement, appearance, equipment, world time, weather and session data between those games.
The project has grown well beyond a prototype: dedicated servers, remote player replication, equipment sync, shared world state, private internet hosting, authenticated public listings, password protection and host moderation controls are all functional. Independent fan project. Not affiliated with Bethesda or Microsoft.
- GameFallout 4 (Anniversary Edition & original)
- ClientF4SE plugin (per-player simulation)
- ServerPython relay + graphical host + Iroh internet transport
- UIPrismaUI / HTML menus (PrismaUI installed separately)
- StatusActively developed, core multiplayer systems functional
Requirements
Anniversary Edition and the original release, both supported
Commonwealth Online runs on both Fallout 4 Anniversary Edition and the original release. You can join a server from either version of the game, alongside players using the other.
DLC, mods and Creation Club content are not required to join or play. You only need optional content when other players in the same session are using it. For example, so their apparel, weapons or world assets can resolve on your client.
Features
Current, active and planned systems
Current
- Dedicated Multiplayer Servers External dedicated server with multiple clients, world-state sync, JSON config and local or remote hosting.
- Visible Remote Players Runtime proxy actors with synchronised position, rotation, cell and worldspace transitions.
- Movement & Animation Idle and movement state, sprinting, sneaking, jumping, weapon-drawn state and teleports.
- Character Appearance Body morphs, tints, hair, head parts, facial sliders and versioned optional data.
- Clothing & Equipment Equipped apparel mirrored across tracked slots, including changes while standing still.
- Ranged Weapon Sync Right-hand weapons with local form resolution, proxy equipping and drawn/holstered state.
- Shared Time & Weather In-game time, days passed, exterior weather and corrections after menus and loading.
- Server Browser Public Browse, LAN discovery, favourites, recent servers, TCP Direct Connect, Iroh invite-code Direct Connect, password prompts and full controller navigation.
- Internet Hosting via Iroh Host from a home PC without router port forwarding or a public IPv4 address. Share an invite code privately or opt into the public server list.
- Graphical Host & Moderation World name, player limit, private/public visibility, invite code, password protection, connection-path status, connected-player list, kick, ban and unban controls.
- Custom Main Menu HTML menu via PrismaUI with multiplayer access, embedded browser, settings and input capture.
- Server-Based Characters Per-server saves, in-game character creation and profile binding on reconnect.
- Development & Hosting Tools End-user graphical host, CLI relay, graphical dev server, fake clients, weather controls, authenticated directory tooling and deployment scripts.
In active development
- Expanded Player Capacity Architecture targets ~16 players long-term with better proxy allocation and performance.
- Animation Refinement Armed locomotion, draw/holster transitions, firing, melee, strafing and jump recovery.
- Weapon & Combat Actions Firing, reloading, melee, grenades, aiming, hit reactions and death/revival events.
- Multiplayer Settings Profile, voice, map/social, network and keybind options with persistent configuration.
- Fallout 4 Settings Bridge Open original Scaleform settings over the Commonwealth Online UI.
- Custom Pause Menu & Map Zoom, pan, player markers and settings panels connected to live game data.
- Expanded Server Administration Build on the shipped kick, ban, unban, password and session controls with richer permissions, remote administration and operator tooling.
Planned
- Multiplayer Map & Markers Local and remote players, friends, locations, quests and custom markers.
- Player Profiles & Gamertags Display names, icons, per-server characters, friends and optional account links.
- Voice & Text Chat Proximity voice, party channels, server text chat, DMs and muting.
- Teams & Social Features Parties, shared markers, invitations and group voice/text channels.
- Interaction Sync Doors, containers, terminals, workbenches, pickups and dialogue with shared vs local rules.
- Enemy & NPC Sync Shared enemy positions, combat state, health, death, loot and basic AI coordination.
- Quest & World Progression Selected quest stages, discovery, cleared locations, workshops and world-state changes.
- Settlement Building Cooperative construction with shared objects, resources, ownership and persistence.
- Power Armour Enter/exit frames, equipped pieces, fusion cores, movement and repair sync.
- Trading & Inventory Player trading, transfers, dropped items, shared containers and validation.
- Mod Compatibility Load-order checks, version negotiation and missing-content warnings when peers use DLC, mods or Creation Club assets you do not have.
- Expanded Public Server Infrastructure Extend the working authenticated public directory with regions, richer filtering, moderation policy and larger-scale operational tooling.
Roadmap
Current progression
- Complete Foundation & world link
- Complete Identity, loadout & session sync
- Complete Terminal UI & hosting operations
- Active Combat & capacity
- Next Player control & server administration
- Future Social layer
- Future A living Commonwealth
Media
Gameplay and multiplayer in action
Community
Follow development and contribute feedback
Commonwealth Online is a working multiplayer framework: dedicated servers, remote player replication, appearance and equipment sync, shared world state, private Iroh hosting, public discovery and host moderation are all in place, and both the Anniversary Edition and the original release of Fallout 4 are supported. Combat, quests, NPCs, settlements, voice chat and large-server performance are actively in development. DLC, mods and Creation Club content are not required unless other players have them. Community feedback and testing interest help shape priorities as systems mature.