According to OpenSignal’s September 2021 report, O2 is the slowest between the 4 major networks in the UK, with an average download speed of 17.1Mbps and average upload speed of 5.4Mbps.
However, O2 has the second fastest 5G speeds, with an average download speed of 91.2Mbps.
O2’s speed is within the same range as Three and Vodafone, with EE being twice as fast as the rest.