Source: Android Central
Best answer: Almost any unlocked phone will work on Fi, but phones that weren't specifically designed for Fi may miss out on certain features like Google's VPN and network switching.
- Unlocked with pure Android and full Fi compatibility: Google Pixel 3a ($350 at Amazon)
- Flexible plans on nearly any phone: Google Fi (From $20 per month at Google Fi)
What phones are designed for Fi?
Source: Android Central
When Google Fi initially launched under the name Project Fi back in 2015, it was only available for the Nexus 6. Google Fi has continued to add its own phones, including the Nexus 5X, 6P, and all Pixel devices. Even Google phones purchased from carriers are fully compatible with Google Fi. Of course, they will need to be unlocked.
These phones are all designed for Fi, which means they will work with Google Fi's VPN as well as automatic switching between Google Fi's three networks. These phones can also connect to over two million approved hotspots to save on data and improve speed. Designed for Fi phones can switch to the best available network without any extra input. Google Fi uses towers from Sprint, T-Mobile, and U.S. Cellular in the United States.
Many of Motorola's phones are designed for Fi as well, including the Moto G Stylus and Moto G Power. There are a few others included, such as the unlocked LG G7 ThinQ. To see if your phone is on the list, check Google Fi's compatibility checker. Look for three green checkmarks for full compatibility.
If you're on a Pixel 2 or newer Google phone, you also get the added benefit of an integrated eSIM that lets you use Fi without having to wait for a physical SIM to arrive in the mail. Uniquely, the Pixel 3a and Pixel 4 can use a physical Google Fi SIM alongside an eSIM to improve network switching performance.
What phones are compatible with Fi?
Source: Andrew Martonik / Android Central
Most unlocked phones will work on Google Fi to an extent but will not work with features such as network switching. These phones will use the T-Mobile network exclusively. Unlocked phones will be able to access T-Mobile's 5G network while connected to Google Fi.
Android phones need to support T-Mobile's GSM network, which is most of them, and they will also need to be running Android 7.0 or newer. Calls over Wi-Fi will work with most Android phones, and texting over Wi-Fi might work. Samsung devices will need to download the Messages app to text over Wi-Fi.
Apple iPhones newer than the 5S will work with Google Fi, and the XR, XS, and 11 series will even be able to use an eSIM. You will need to update your phone to at least iOS 11 to activate. iMessage will work right out of the box since it uses data for transmission, but texts to other brands, the green texts, will need a few additional settings to get working. Apple device ill get access to international data but won't be able to call or text over Wi-Fi. You also won't be able to use your hotspot outside the US on an iPhone.
Ultimately, Google Fi is a great prepaid network regardless of which phone you're using it on. While there are still advantages to using a phone specifically made for Fi, we're just happy that it's finally open to any device that supports its network partners.