Britain’s ‘worst’ mobile network with slowest download speed is revealed

THE best and worst of British mobile networks have officially been ranked.

Four major UK providers were judged based on their download and upload speeds.

Whether you’re streaming movies on the go, gaming online, or video calling friends, rapid download speeds are a huge draw when choosing a mobile network.

And latest tests from the team at Ookla have officially determined the best and worst providers for upload and download speeds.

Three Mobile beat its main rivals to the top spot, scoring high marks for both uploads and downloads.

The provider scored an average of 214Mbps for downloading files, over 80Mbps quicker than its closest rival.

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Meanwhile, O2 was at the bottom of the pack across all categories, with the slowest speeds overall.

The provider recorded a speed score result of 30.70, compared to Three’s 53.46.

Its average download speeds were logged as 78.92Mbps, while uploads were found to be 8.28Mbps.

“The Ookla Speedtest Award for Fastest Network is based on Speed Score and provides a measure of a network’s throughput and responsiveness,” Ookla explained.

The rest “combines download and upload speeds with latency metrics to give an overall view of speed performance”.

However, it is worth mentioning that scores may not accurately represent speeds across the entire county.

Team at ISPreview noted that it can be difficult to obtain an accurate assessment with users constantly moving and accessing networks indoors and outdoors, as well as changing environments.

An O2 spokesperson told The Sun: “As part of our Mobile Transformation Plan, we’re investing more than £2m every day into our mobile network to improve the services we provide our customers.

“This includes expanding our 4G and 5G coverage via our dedicated small calls rollout which will boost capacity in dense urban areas, as well as innovative solutions to address network pain points in traditionally hard to serve areas like airports and motorways.

“Through this investment, and through acquiring more spectrum, we’re delivering a better network experience for our customers.

“This was reflected in O2 being recognised as the most improved mobile network across Europe in Umlaut Connect’s Mobile Network Test, and being named Best Mobile Network Coverage in Uswitch’s 2025 Awards.”