Google Fi, formerly known as Project Fi, is an American MVNO (Mobile Virtual Network Operator) telecommunications service by Google. It provides telephone calls, SMS, and mobile broadband using cellular networks and Wi-Fi. Google Fi uses the T-Mobile network and is available only to US residents. It was initially launched for the Nexus 6, by invitation only, on April 22, 2015, and was opened to the public on March 7, 2016. The service has since been expanded to work with additional device models, including the Pixel and Pixel XL smartphones, and partially with iPhones. In 2023, it was renamed Google Fi Wireless.

Google Fi offers fixed prices that dont unexpectedly change, unlimited data and texts in the US and over 200 countries or regions, and free calls from the US to over 50 countries, regions, and territories. It also provides up to 50 GB of free, unmetered data, with data speed slowing to 256 kbps after 50 GB of use per person. Additionally, it offers full-speed hotspot tethering at no additional cost and 100 GB of Google One storage per person at no additional cost.

Google Fi allows users to claim up to four data-only SIMs for their account and use them in any devices they want. It is known for its flexibility and can be a cost-effective option for certain styles of smartphone usage. However, it may not make sense for everyone, so potential users should consider their specific needs and usage patterns before deciding if Google Fi is right for them.

In summary, Google Fi is a wireless phone plan service that offers flexibility, international roaming, and fixed prices, making it a potentially attractive option for certain users in the US.