No network wins Northampton on coverage. All four are within 2 points of each other in Ofcom's measurements, across 1,121 addresses sampled in 45 postcodes. On a difference that small, EE, O2, Three and Vodafone will all work here — so choose on price, contract length and roaming, not on a coverage map. Coverage only becomes the deciding factor once you leave built-up areas, and it still varies street by street indoors: check your own postcode below to see the measurement for your address rather than for Northampton as a whole.
Ranked by Ofcom's overall score: EE 100, Three 100, O2 99, Vodafone 98. The spread between best and worst is 2 points, which is inside the margin where a coverage figure stops being a useful tiebreak. Ofcom's data describes outdoor signal across sampled addresses; it cannot tell you how any of them behave inside your own building.
These scores for Northampton are Ofcom's own measurements, taken from the Ofcom Mobile Coverage API (May 2025 data) across 1,121 addresses in 45 postcodes. They describe outdoor signal at sampled addresses across the whole of Northampton; signal inside a specific building, and on a specific street, can differ from the area figure.