What We Know About Google Fi's Mystery Second 5G Partner

Google, based in Mountain View, California, in the United States, said this week that its Fi mobile service now connects to a second 5G network, ending a multiyear run as a single-carrier operation, according to Ars Technica. The company has not identified the new partner.

What is Google Fi's "super network"?

Google's blog post describes the upgrade as a "super network" that will let phones "hop between T-Mobile 5G and a different 5G network to provide the best possible connectivity," Ars Technica reported. The post, Ars Technica noted, does not name either carrier, stating only that Fi now supports "two of America's best 5G cellular networks." Google has operated Fi on a single network — T-Mobile — since T-Mobile absorbed Sprint, after launching in 2015 as Project Fi with both T-Mobile and Sprint service tied to Nexus handsets that switched between towers based on signal strength, the outlet said.

Which carriers power Google Fi now?

T-Mobile remains confirmed. The identity of the second carrier is not. Ars Technica's Ryan Whitwam wrote that the partner "must be either AT&T or Verizon," since those are the only other nationwide 5G networks in the United States. Examining Fi's published coverage map, Whitwam concluded that "the shape of unserved regions is a closer match" to Verizon than to AT&T, while cautioning that carriers "do tend to fudge the fine details of these maps." That assessment is an inference from public coverage data, not a confirmation from either company.

Why won't Google name the second network?

A Google spokesperson, asked directly by Ars Technica, declined to name the second network. The outlet called the refusal "odd," noting that Google was previously forthcoming about its T-Mobile relationship, including the fact that Fi subscribers receive top prioritization on T-Mobile towers — a detail that distinguishes Fi from most mobile virtual network operators, which typically get lower queuing priority than a carrier's own customers during congestion.

That openness has receded. Ars Technica reported that Google's own Fi FAQ page "no longer even confirms T-Mobile as a network partner," a shift the outlet linked to a broader pattern: carrier-identifying details in MVNO support pages and FAQs have become harder to find industrywide. Whitwam argued that network information "is really something consumers should have when shopping for plans," since coverage quality varies sharply by location and carrier.

Which phones support the new dual-network switching?

The feature is limited at launch. According to Ars Technica, automatic network switching currently works only on Google's own Pixel 9, Pixel 10, and Pixel 11 series. Owners of other phones will have to wait until 2027 for access, the outlet reported, without further detail on which additional devices are planned.

There is also a configuration requirement. Ars Technica reported that the super network will not work with conventional dual-SIM setups. Subscribers must run Fi as an eSIM with all other, non-Fi SIMs disabled for the network-hopping feature to function. Phones using a physical SIM alongside Fi, or a second active eSIM for another carrier, will not get the switching behavior.

What are the costs and plan requirements?

Google is rolling out the feature at no additional charge, according to Ars Technica, but only on two of Fi's tiers: Unlimited Premium and Flexible plans. The report did not specify whether Fi's other plan options will gain access later, nor did it give a timetable beyond the 2027 device-expansion window already noted for non-Pixel phones.

What to watch

• Whether Google or a carrier eventually confirms the second network's identity, resolving the Verizon-versus-AT&T question Ars Technica raised from coverage-map analysis alone.
• Whether Fi extends automatic network switching beyond the Pixel 9, 10, and 11 lines in 2027, and to which specific devices.
• Whether Fi broadens eligibility beyond Unlimited Premium and Flexible plans, or requires users on other tiers to upgrade for dual-network access.
• Whether other MVNOs follow Fi's lead in obscuring carrier partnerships in FAQs and marketing material, a trend Ars Technica says is already spreading across the industry.

For now, Fi subscribers meeting the eSIM and device requirements can switch on the feature, but they will be doing so without official word on exactly which second tower network their phone is reaching for.