What Was Found in the 12TB Steam Leak: Early Builds of GTA 3, Mafia 2, and Valve Games

When 12 terabytes of old files from Valve's systems spilled online in late August, the headlines instantly promised Half-Life 3, "a decade of cancelled games," and stolen source code. More than a week later, with enthusiasts having gone through the archive in detail, the picture turned out both smaller and more interesting. Here's what's really in this leak — far from just Valve's games — and what turned out to be wishful thinking.

Over the weekend of August 29, an archive of about 12 terabytes started making the rounds: old game builds and assets from Valve and its partners across a decade, from 2003 to 2013 (our first report on the leak). The community quickly dubbed it the "Steam2 Teraleak."

The key thing to grasp: this wasn't a cyberattack. According to data miner Gabe Follower, who reported on the archive, the data was sitting on an open server tied to the old Steam2 system — the one Steam used to deliver game content before moving to SteamPipe in 2013. He says the server could be reached without authentication. That also explains the cutoff: after the 2013 move to SteamPipe, nothing new was added to the old storage. Exactly when the archive was pulled, and whether it was assembled from a single source, isn't established — some researchers think it's a long-accumulated collection. The "this is Valve's own fault" line is, likewise, Gabe Follower's read, not the company's position.

There's some confusion about size: some say 12 TB, others 13. That's not a contradiction, just different units for the same amount. For the contents, the most reliable figure is the depot count — the verified public catalogue lists 10,876 Steam2 depots. Even that isn't the same as a game count, though: a single depot can bundle many entries — one of them, for instance, points to some 2,700 "games," mostly old trailers.

Here's the genuinely interesting part. Steam2 stored content not just from Valve but from every publisher that distributed games through it before the SteamPipe migration. So alongside Portal and Half-Life builds, the archive holds prototypes and early versions from entirely different studios.

Hidden Palace archivists have extracted the following builds, according to Ars Technica:

A word of caution about the long lists of "confirmed" games spreading across aggregators, though. Steam2 depots are chains of update files: to assemble a working version you need every link, and often some are missing. So an index entry, a handful of loose assets, and a runnable build are three very different things. Names like Alan Wake, Batman: Arkham Asylum, Dragon Age: Origins, Mirror's Edge and Fallout: New Vegas do appear in the depot listings, but there's no confirmed playable build for any of them so far — at best a few scattered files.

There's an uncomfortable side to these finds, easy to overlook amid the talk of "lost treasures." It's all someone else's intellectual property: raw, scrapped work that its creators buried years ago has become publicly available and can no longer be fully removed from the internet. And this isn't only about Valve — the archive holds material from Rockstar, 2K, Sega, Paradox and dozens of other studios that nobody ever meant to publish.

Data miner Tyler McVicker put it plainly: it's precisely the volume of third-party content that makes this more dangerous than if only Valve's own builds had leaked. Interests diverge here — archivists see lost gaming history being saved, while rights holders see their material distributed without consent. And with not one of the affected studios saying anything publicly, the question stays open.

Valve's own games are in the archive too, of course, and that's where the finds are richest. The most fleshed-out is an early version of Portal 2, down to traces of the cancelled prequel F-Stop. That's a whole story of its own: our deep dive into the early Portal 2 is a separate piece.

Beyond that, Valve's own builds include a working Left 4 Dead from 2008 and an early version of CS:GO — from the days when it was still essentially a Counter-Strike: Source mod.

The fans' biggest fixation was a 3D model of a weapon called the Weaponizer, long tied to the cancelled Half-Life 2: Episode 3. But that doesn't establish that an Episode 3 build exists anywhere: the model has been known since 2011 — from the "ep3" folder in the Dota 2 beta and Valve's Half-Life 2 20th-anniversary documentary — and it lingered in Portal 2's files as a placeholder.

A big chunk of the hype around this leak is about things that turned out not to be in it at all.

Half-Life 3. No confirmed Half-Life 3 material has turned up in the parsed archive. Every breathless "HL3 leak" headline is trading on the name alone.

A playable Half-Life 2: Episode 3. One weapon model was found, not a build. A model isn't a game.

Source code. The archive holds compiled builds, assets and 3D models — not the source code of the engine or the games. CS:GO and TF2 source code did leak, but that was a separate affair back in 2019, unrelated to this one.

User data. This is a leak of game content, not of Steam's servers. No accounts, no payment details, no purchase history are in the archive.

Previously unknown cancelled Valve games. From cancelled projects, the archive holds material from the already-known F-Stop; no previously unknown cancelled Valve projects have been confirmed. The loud "a decade of buried projects" headlines rest on that same F-Stop, while other legendary cancelled projects — Prospero, Stars of Blood — never surfaced in the leak: they're known from entirely different sources, and pinning them on this archive is simply wrong.

Strip away the hype and the Teraleak's value isn't "hidden masterpieces" — it's a rare look at the development process: games in the rough, with placeholders, abandoned ideas and dead ends. Former Valve developer Elan Ruskin put it more honestly than anyone: every good idea the team had made it into the shipped game, and whatever got left behind wasn't a good idea to begin with.

But it's the sheer scale that creates serious legal risks here. Old builds of Valve's own games are one thing; other studios' prototypes, which their authors never meant to show, are quite another. As of mid-September 2026, Valve has not publicly commented on the leak, and no reports of takedown demands have appeared; the public catalogue of finds keeps growing. How the industry squares preserving its own history against studios' right to their own secrets is a question this leak doesn't answer. This leak has only made that conflict harder to ignore.

It's a leak of roughly 12 TB of old builds and assets from Valve's Steam2 content-delivery system, spanning 2003–2013, which surfaced in late August 2026. According to data miner Gabe Follower, it wasn't a hack: the files were sitting on an open server with no protection.

Extractable builds are confirmed for GTA 3, Mafia 2, Spec Ops: The Line, Civilization 5, Crusader Kings 2, Duke Nukem Forever, Plants vs. Zombies and Sonic 4: Episode 2. A number of other games appear in the depot index, but there are no confirmed playable builds for them.

No. No confirmed Half-Life 3 material has turned up in the archive. Only a model of the Weaponizer weapon, tied to the cancelled Episode 3, was found — and there's no playable Episode 3 build in the archive either.

No. The archive holds compiled builds, assets and models, not source code. CS:GO and TF2 source code leaked separately in 2020 — a different event.

No. This is a leak of game content from old servers, not Steam data. Accounts, payment information and purchase history are unaffected.

As of mid-September 2026, Valve has not publicly commented on the leak, and no takedown demands have been reported. None of the affected third-party studios have spoken publicly either.