Oahu has strong 4G and 5G coverage from T-Mobile, AT&T, and Verizon. Honolulu's Waikiki Beach neighborhood has strong 4G and 5G coverage. The area from Ala Moana Center through Waikiki to Diamond Head Crater has consistent signal.
Downtown Honolulu, Chinatown, and the Ala Moana shopping district are fully covered. The H-1 Freeway corridor has 4G throughout. Pearl Harbor National Memorial has strong outdoor coverage. The North Shore towns of Haleiwa, Sunset Beach, and the Banzai Pipeline area have 4G.
Kailua, Kaneohe, and the Windward Coast have solid 4G along the main Kamehameha Highway. Mountain areas like the Manoa Valley trailheads and Nuuanu Pali Lookout have variable signal. The Waianae Coast on the west side has 4G in towns but weaker coverage on beaches north of Kaena Point.