US Mobile piggybacks on Verizon and T-Mobile's networks. US Mobile brands its Verizon-based service as Warp 5G and it's T-Mobile-based service as GSM. You can check which service US Mobile recommends for you with the carrier's coverage tool.

Warp 5G vs. GSM

US Mobile usually tracks users onto its Warp 5G service. Warp is right network for most people thanks to Verizon's network. That said, US Mobile's GSM service can be a better choice for some subscribers. T-Mobile's network has an edge in certain areas, and sometimes devices have better compatibility with T-Mobile.

US Mobile 5G Coverage

The 5G in Warp's branding is a bit confusing. Warp 5G uses both Verizon's 5G and Verizon's 4G LTE services. In fact, Verizon covers significantly more area with 4G than 5G.

US Mobile's GSM service isn't limited to 4G—it uses T-Mobile's 5G network as well. While T-Mobile lags behind Verizon in overall coverage, T-Mobile offers more square miles of 5G coverage than Verizon. By default, the map shows both 4G and 5G coverage, but you can switch to the 5G-only map.

Roaming Partners

The coverage maps may not include all of Verizon and T-Mobile’s roaming partners. I expect that US Mobile customers generally don’t have access to coverage from these partners, but I have not confirmed with US Mobile.

Crowdsourced Coverage Maps

Coverage Critic offers crowdsourced maps of coverage for the networks underlying both the Warp and GSM services. You can toggle the crowdsourced map in the settings. The density of crowdsourced data is highest in urban areas.