Project Fi is a mobile virtual network operator by Google, providing phone, messaging and data services using both Wi-Fi and cellular networks belonging to Sprint, T-Mobile, U.S. Cellular, and Three (U.K.). The service was launched on April 22, 2015, for the Nexus 6 through invitations only. The invitation system was dropped in March 2016, and support for additional devices, including the Pixel and Pixel XL smartphones, was introduced in October 2016.