In 2004 Valve released the Steam platform for Windows computers (later expanded to Mac OS and Linux) as a means to distribute Valve-developed video games. Steam has the speciality that customers don't buy games but instead get the right to use games, which might be revoked when a violation of the End-user license agreement is seen by Valve[14] or when a customer doesn't accept changes in the End-user license agreement.[15][16] Steam began later to sell titles from independent developers and major distributors and has since become the largest PC digital distributor.