Play Fallout with a friend. This is a fan-made two-player co-op mod for Fallout 1, built on Fallout Community Edition. Player 1 hosts the game; player 2 joins over a LAN, the internet, or on the same PC, with their own character.
Built with AI. The code, tests and docs were written by an AI coding assistant (Claude, by Anthropic). A person decided what to build, played it and set the priorities. How it was made explains the process.
You need your own copy of Fallout (GOG or Steam). No game files are included. Co-op is off by default: without it the game plays exactly like Fallout CE.
Co-op lives in Fallout's own main menu: MULTIPLAYER opens hosting, joining, one-PC play, updates and bug reports.
Download the package for your system under Releases, or build it yourself (see the end of this page).
Unpack it into a folder of its own (not into the Fallout folder) and run it:
- Windows:
fallout-ce.exe. It isn't code-signed, so SmartScreen may warn; choose More info → Run anyway. - Linux: needs SDL2 (
sudo apt install libsdl2-2.0-0), then./fallout-ce.
The first start shows a setup screen that finds your Fallout installation (GOG, Steam and others) and reads the game from there. Then pick MULTIPLAYER in the main menu. Without a co-op server (see docs/coop/SERVER.md) you play on a LAN, on one PC, or online by entering the host's address.
For more about the engine itself (other platforms, fallout.cfg,
f1_res.ini), see Fallout CE's README.
- COOP.md: how to play, the rules, and the settings
- docs/coop/ARCHITECTURE.md: how it works
- docs/coop/SERVER.md: running your own server (server list, relay for online play, updates, bug reports); the game works without one on a LAN or with a direct address
- docs/coop/TESTING.md: the automatic tests
- docs/coop/HOW-IT-WAS-MADE.md: how it was built, and why it works the way it does
- CONTRIBUTING.md
- ROADMAP.md: Fallout 1 now, then Fallout 2, then big Fallout 2 mods (Sonora, Nevada, Olympus 2077)
- Ideas: what could come next; comment or add a 👍 to the ones you want
Build with cmake -B build && cmake --build build (needs SDL2), or build
the Linux and Windows packages with tools/build-release.sh.
Unofficial. Not affiliated with or endorsed by Bethesda Softworks, ZeniMax, Microsoft or Interplay. Licensed like Fallout CE under the Sustainable Use License (free, non-commercial).