Ultra Mobile runs over T-Mobile's network. Subscribers with Ultra Mobile have access to both 4G and 5G coverage from T-Mobile.
The map reflects predicted outdoor signal quality. Indoor signal, congestion, and roaming aren't mapped. Each can matter in practice.
Cell coverage data for Ultra Mobile comes primarily from the November 2025 release of the FCC's Broadband Data Collection program (representing networks as of June 2025), supplemented with real-world measurements from large crowdsourcing projects.