T-Mobile, AT&T, and Verizon each provide 5G deployed across Downtown Boston, Back Bay, the Seaport Innovation District, Cambridge, and the main university corridor. Newbury Street, the Public Garden, and the Freedom Trail's main historic sites all have strong outdoor signal.
Harvard Square and MIT's campus in Cambridge are fully covered. The Seaport District, which houses many biotech and tech companies, has dense 5G. Boston's MBTA subway (the T) has partial coverage at stations, with older underground sections having limited platform coverage.
The Green Line underground stations have variable signal. Surface sections of the MBTA have consistent 4G. Boston Logan Airport has full 5G coverage across all terminals. The SL1 Silver Line bus connecting Logan to South Station is an above-ground route with reliable coverage.