Microsoft announced the Xbox Game Pass on February 28, 2017 and made a limited number of games available to select members of the Xbox Insider community for testing and feedback purposes.
The service launched June 1, 2017 whilst subscribers of Xbox Live Gold were allowed access on May, 24 2017.
An Xbox Live Gold subscription is not required for the Pass, but it is required for online multiplayer content in games.
Microsoft's E3 2017 press conference saw them introduce select Xbox titles would be available similar to Xbox 360 titles, it was later stated that some of those games could make it onto Game Pass.
First Party on Game Pass
January 23, 2018 saw Microsoft expand Game Pass by adding all future Microsoft first-party titles to the Game Pass day and date with the retail release. Sea of Thieves was the first new title to appear on Game Pass on March 20, 2018.