held conferences called Steam Dev Days from 2013 to 2014. In 2014, Ubisoft games started to require Uplay to run after launching the game from Steam. In 2019, Ubisoft announced that they would stop selling their future games on Steam starting with Tom Clancy's The Division 2 because Valve would not modify its revenue sharing model, with the company simultaneously announcing a deal with Epic Games to start selling their games on the recently launched Epic Games Store in addition to uPlay (which would later be rebranded to Ubisoft Connect). In May 2019, Microsoft distributed its games on Steam in addition to the Microsoft Store. In 2020, EA started to publish select games on Steam, and offering its rebranded subscription service EA Play on the platform. In 2022, Ubisoft announced that they would return to selling its recent games on Steam after leaving the storefront in 2019, starting with Assassin's Creed Valhalla, citing that they were "constantly evaluating how to bring our games to different audiences wherever they are". By 2014, total annual game sales on Steam were estimated at around $1.5 billion. By 2018, the service had over 90 million monthly active users. In 2018, its network delivered 15 billion gigabytes of data, compared to less than 4 billion in 2014. Features and functionality Software delivery and maintenance Steam's primary service is to allow its users to purchase games and other software, adding them to a virtual library from which they may be downloaded and installed an unlimited number of times. Initially, Valve was required to be the publisher for these games since they had sole access to the Steam's database and engine, but with the introduction of the Steamworks software development kit (SDK) in May 2008, anyone could integrate Steam into their game without Valve's direct involvement. Valve intended to "make DRM obsolete" as games released on Steam had traditional anti-piracy measures, including the assignment and distribution of product keys and support for digital rights management software tools such as SecuROM or non-malicious rootkits. With an update to the Steamworks SDK in March 2009, Valve added its "Custom Executable Generation" (CEG) approach into the Steamworks SDK. The CEG technology creates a unique, encrypted copy of the game's executable files for the given user, which allows them to install it multiple times and on multiple devices, and make backup copies of their software. Once the software is downloaded and