Google Fi adds a second 5G network but will not name it

What Google announced

Google has announced what it calls a super network upgrade for its Fi mobile service, according to Ars Technica. The move makes Google Fi a dual-carrier service in the United States again, with phones able to move between T-Mobile 5G and a second 5G network to find the strongest connection.

The unusual part is that Google will not say which carrier the second network belongs to. Its announcement mentions only two of America's best 5G cellular networks, and a Google spokesperson declined to name the partner when asked.

The history behind the change

Google Fi launched in 2015 as Project Fi, a mobile virtual network operator, meaning a service that rents capacity from established carriers rather than running its own towers. At the start it worked on both T-Mobile and Sprint, and only on Google's Nexus phones, which switched between networks based on signal strength.

After T-Mobile absorbed Sprint, Fi became a single-network service in the US, though it still hopped between networks when travelling abroad. The new upgrade restores dual-carrier operation at home.

Who might the mystery partner be

Since one network is T-Mobile, the other must be either AT&T or Verizon. Ars Technica suggests the partner is more likely Verizon, because the shape of the unserved areas on the Fi coverage map looks closer to Verizon's footprint than AT&T's. That remains a guess, and carriers often draw their coverage maps in ways that hide fine detail.

Google has also become less open about its network partners in general. Its Fi FAQ no longer confirms T-Mobile as a partner, even though Google once highlighted that Fi received top prioritisation on T-Mobile's towers, something few other virtual operators could claim.

Limits of the rollout

There are several caveats. Network switching currently works only on the Pixel 9, Pixel 10 and Pixel 11 series, with other devices due to gain support in 2027.

Traditional dual-SIM use is also off the table for anyone who wants Fi to switch networks. The service must be set up as an eSIM, a digital SIM built into the phone, with every other SIM disabled.

What it means for customers

Eligible customers on Unlimited Premium or Flexible plans get the super network at no extra cost, and it is rolling out now.

For shoppers, the unnamed partner is a real problem. Most people know which carriers work well in the places they spend time, and that information matters when choosing a plan. Virtual operators have generally become less forthcoming about which networks they use, and Google's silence here fits that trend.