AT&T, Verizon, Sprint and T-Mobile all have large networks with varying amounts of coverage. Visiting OpenSignal.com and entering a ZIP code can determine the best carrier for that location. Cellular phone reception depends upon the level of coverage a carrier has in the area where a phone is used.
Open Signal ranks cellular coverage in an area compared to other providers as well as to the U.S. average. Searches can be refined to specific addresses and technology types, such as only 3G if a phone does not have 4G capabilities. If a phone is used in multiple areas or must travel, zooming out from the map or searching multiple addresses can help to find a carrier that offers good coverage in all areas where the device is used.
While most cellular carriers brag about their coverage, the metrics they use can be very different or misleading. Some carriers offer the best coverage in areas of dense population, while others have better reception in rural areas. Additionally, phone call reception is not the same as data access speeds, and some provider networks may have good voice coverage but limited data coverage in a region. Some providers have better market capitalization in specific regions and have better coverage as a result.