Steam experiences a massive data breach, potentially the largest in gaming history.

A leak from a multi-billion dollar company like Valve is a significant event, but what transpired on August 29 was more than just a typical leak; it was a major information breach impacting nearly all prominent video game companies that released titles on the Steam platform during a specific period.

Here’s what we’ve gathered so far.

Reports indicate that the leak consists of a staggering 12 terabyte file containing internal builds of every game uploaded to Steam between 2003 and 2013. This breach encompasses Valve’s own franchises, such as Portal and Half-Life, along with beta versions of games from various publishers, both large and small. Enthusiasts have already uncovered early builds or files related to franchises like Call of Duty, Resident Evil, Sonic the Hedgehog, Mirror’s Edge, Batman: Arkham Asylum, Dragon Age: Origins, Spore, and many others.

The sheer volume of information in this leak is enormous, making it difficult to ascertain the total number of prototypes and pre-release materials included. So far, the most documented findings relate to Valve’s titles. Fans have discovered unused maps, early weapon concepts, character designs that never made it to the final game, and previously unseen gameplay footage. Notably, there’s footage of a Portal 2 build featuring a “bullet time” mechanic that slowed down time during puzzle-solving. Additionally, the discovery of cut dialogue for Cave Johnson’s Companion Cube from Portal 2 has surprised fans, as it supports long-held theories about the Companion Cubes’ role in the series.

Valve has yet to comment on the situation, but users exploring the files on social media assert that this incident did not involve hacking or theft. The files were reportedly accessed through a publicly available website that previously served as Valve’s storage solution before the company transitioned to a more secure system.

Among the findings is a build for a game called F-Stop, which seems to be set in the Portal universe. Early models and concepts suggest it was a version of Portal 2 focused on camera mechanics. While dedicated Valve fans have known about F-Stop for some time, the lack of detailed information surrounding it made it a greater mystery than the elusive Half-Life 3.

As for Half-Life 2: Episode 3, yes, there is content in the leak related to this long-awaited conclusion to the iconic FPS series. HL2E3 was announced by Valve in 2006 but was ultimately canceled a few years later due to creative challenges. The game was intended to take place in the Arctic and was rumored to feature ice-related mechanics. Fans have already found data strings and media in the leak referencing items like an ice gun and a “Weaponizer” gun, which were mentioned in the Half-Life 2 20th anniversary documentary. Given the leak’s vastness, more discoveries are likely to emerge in the coming days.

The extent of the material uploaded to Steam between 2003 and 2013 will determine what fans can find. For some titles, early builds closely resemble the final versions, while others may contain only minimal assets that don’t reveal much. In certain cases, fans have successfully run unreleased beta builds of games like Sonic the Hedgehog.

Soul’s Remnant is an MMORPG developed by two individuals that is making waves on Steam.