Valve’s canceled Portal prequel F-Stop leaks online, as gamers show off multiple playable levels

Most avid PC gamers probably know just how popular Valve’s two Portal puzzle games are, but only a small percentage may have heard about F-Stop – a prequel to the first Portal game that was reportedly in development around 2007, shortly after the first Portal was released as part of The Orange Box collection (and became an instant hit). However, it didn’t feature the iconic Portal gun.

F-Stop was developed during a company-wide game jam known as the Directed Design Experiments. Instead of using the Portal gun, players have access to an experimental Aperture Science camera, allowing them to photograph objects to freely move and resize to another location. “In Layman’s terms, this camera imprisons an object’s soul ’til you’re good and ready to free it,” says the game’s introduction voice-over, from a much younger Cave Johnson, the founder and CEO of Aperture Science.

The reconstruction of F-Stop is possible due to a few factors. First of all, a major leak in August 2026 saw around 12 TB of historical Steam depot data surface online, including original assets from the abandoned title. However, due to a lack of map files and source code, they remained just that. In late October, those missing parts of the puzzle made their way into the Valve Cut Content Discord server.

What was F-Stop abandoned?

Despite the neat photography theme, F-Stop was reportedly abandoned after playtesters were disappointed by the lack of a Portal gun. It was supposed to be set in the same universe, after all. The game was due to be set in the early years of Aperture Science, supposedly in the 1940s-1950s. Valve did end up exploring the company’s past in Portal 2 during underground sections, guided by Cave Johnson’s pre-recorded messages.

Of course, this project is long-abandoned and what remains are a few early prototypes. That being said, it’s nice to see it being showcased nearly 19 years later thanks to leaked game files, assets, and most importantly, the source code. The concept shares similarities with games such as Superliminal and Viewfinder, but it just goes to show that Valve was experimenting with these mechanics years before either was released. Some of F-Stop’s characters, dialogue, and ideas were eventually reused in Portal 2.

Written by

Jack Goodall

At PC Guide, Jack is mostly responsible for reporting on hardware deals. He also specializes in monitors, TVs, and headsets and can be found putting his findings together in a review or best-of guide.

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