Steam

Steam is a digital distribution, digital rights management, multiplayer and communications platform developed by the Valve Corporation. It is used to distribute games and related media online, from small independent developers to larger software houses (including Valve themselves who also releases their games on Steam). Steam also has community features, automated game updates, and in-game voice and chat functionality.

Each Sonic the Hedgehog games can be used by the In-Game community feature, allowing the player to take screenshots and replays to be posted in the Community Hub.

Trivia

 * Sonic & SEGA All-Stars Racing is the Sonic game to be released on Steam.
 * All of the Sonic the Hedgehog games besides Sonic Spinball, Dr. Robotnik's Mean Bean Machine and Sonic 3D Blast Steam has put online are also all available on the Xbox 360 and PlayStation 3.
 * Sonic Heroes is the only major PC release of the Sonic series that was not released on Steam.
 * Sonic & All-Stars Racing: Transformed is the only Sonic game on Steam to feature online multiplayer.
 * Sonic & All-Stars Racing: Transformed, Sonic Generations and Sonic Adventure 2 are the only games on steam to feature individual downloadable content.
 * The SEGA War Bundle is the only item which was removed from the Steam store. It was removed on February 27th 2013.