Short answerO2 is part of Virgin Media O2. giffgaff, Tesco Mobile and Sky Mobile all run on the O2 network. O2 data SIMs for routers are available as business, IoT and fixed IP SIMs. O2 was the last UK network to switch off 3G, so make sure any older device on O2 supports 4G.
O2 combined with Virgin Media in 2021. It launched 4G in 2013, after the spectrum auction that also brought O2 its 800MHz coverage band.
O2 SIMs for routers
- Business data SIMs: for offices, shops, sites and backup broadband.
- Fixed IP O2 SIMs: for remote access to cameras and controllers. See O2 fixed IP SIMs and our fixed IP guide.
- IoT SIMs: pooled data and SIM management for estates of devices. See IoT and multi-network SIMs.
The end of O2 3G
O2 switched 3G off area by area through 2025, starting in Durham, with the last areas following into early 2026. Devices that rely on O2 3G for data, including some older alarm diallers, payment terminals and routers, need replacing with 4G kit. See our switch-off guide.
Bands
O2 uses several bands for 4G, including 800MHz for coverage and 2.3GHz (band 40) for capacity in busy areas. Make sure your router supports the UK bands in our bands guide.
Checking coverage before you commit
Use two sources and then test on site. Ofcom’s Map Your Mobile checker compares all four networks for a postcode. Each network also publishes its own map. Neither tells you what a router inside a cabinet will see, so put a SIM in a phone or router at the exact spot and read the values with our signal checker.
Frequently asked questions
Does giffgaff use O2 masts?
Yes. giffgaff, Tesco Mobile and Sky Mobile use the O2 network.
Can I use a giffgaff SIM in a router?
Check giffgaff’s current terms for router and tethering use. For business equipment, a business data SIM on O2 is usually the better choice.
Has O2 switched off 3G?
Yes, in stages through 2025, with a small number of sites lasting into early 2026.
NANick Appleby
Nick Appleby has worked in UK telecoms since 1998, starting at BT, and has spent most of that time on cellular routers, data SIMs and the antennas that connect them for business and industrial sites. He writes 4G SIM to explain how the networks and the kit actually behave, in plain English.