Google Fi is a mobile virtual network provider (MVNO) that provides voice calling, texting, and mobile broadband services. Based in the United States, it works primarily with US-based mobile carriers, but you can use it for international calling and international data is also available. Coverage and service are comparable to those of major carriers, while prices are in line with lower-cost MVNOs. Google Fi works with most modern phones, including Android devices from most manufacturers, as well as the iPhone.

Google Fi originally launched as Project Fi on an invite-only basis in 2015, before opening to the public in 2016. When it launched, it was only compatible with the Nexus 6, with the public launch adding the Nexus 5x and the Pixel line. Compatibility has since expanded to most Android devices in addition to the iPhone, though Google only offers personalized customer support and troubleshooting for a fairly short list of devices.

As an MVNO, Google Fi manages to use other carriers’ mobile networks instead of building its own. In the United States, Fi has partnered with T-Mobile, Sprint, and US Cellular, allowing users to seamlessly switch between networks as they travel.

When you sign up for Google Fi, they are your mobile service provider. Your voice and data will be sent over the T-Mobile, Sprint, or US Cellular network, but Google will track your usage and Google will bill you.