Leaked F-Stop Prequel Becomes Playable
Valve's cancelled 2007 Portal prequel F-Stop has surfaced online and can now be played after community members combined three separate leaks.
Updated on Nov. 1, 2026 in eSports
F-Stop, a Portal prequel developed by Valve in 2007 and later scrapped, was leaked online and has been assembled into a playable version. The leak combined roughly 13 terabytes of Steam depot data with mapsrc data and source code shared via the Valve Cut Content Discord server.
Why it matters
The release gives players access to content Valve never shipped, and offers a rare look at development material behind Portal 2. Some of F-Stop's dialogue, characters and mechanics were reworked into that game.
The leak consists of roughly 13 terabytes of Steam depot data, with F-Stop assets contained in the Steam2 leak but its source code and mapsrc data arriving separately via Discord. The community's playable build is estimated at 99 percent complete, though the remaining gaps have not been detailed.
The players
Valve
Valve is the game developer behind Portal, Portal 2 and the cancelled F-Stop prequel, and operates the Steam platform.
The details
F-Stop was one of five experiments Valve pursued during three months of Directed Design Experiments in 2007. Its experimental Aperture Science camera manipulated perspectives to solve puzzles, and the project was scrapped before release.
Timeline
2007: Valve develops F-Stop during the Directed Design Experiments project.
Late August: Roughly 13 terabytes of Steam depot data leak as Steam2.
Past 48 hours: F-Stop mapsrc data and source code are leaked via the Valve Cut Content Discord server.
Development Archive
The leak reveals how the material cut from Portal 2 was reworked into the finished game, as seen in F-Stop's dialogue, characters and mechanics. It gives fans a rare look at an earlier stage of Valve's Portal development than the released titles show.
Players can now download and run a community-built version of F-Stop, a game that was never officially released. The build is described as roughly 99 percent complete, so access depends on the community's distribution of the leaked files.
The takeaway
Unreleased material from a game's development can resurface years later and change how fans understand the finished product. Readers following game preservation should note that leaks can preserve work that studios have set aside.
Further reading
Explore more eSports coverage for context on gaming communities and leaked game content.
