Three UK has quietly introduced speed caps across most of its new mobile and mobile broadband plans. The change took effect on 19 April 2026 and applies to new customers and those upgrading. Existing customers within their minimum term are not affected. The cap will be shown on the plan page when you click through to Three from any of the affected deals, so check the speed details (for example "up to 100Mbps" or "up to 25Mbps") before you commit to a contract.
About the author: Phil Brown is the founder of SIM Only Finder. Phil previously worked in UK mobile retail at Three UK, advising customers on SIM plans, contracts, and network choices. He has spent over a decade running consumer comparison platforms and reviews networks and SIM-only deals based on that hands-on industry background. More about Phil
Last reviewed: 27 April 2026.
What has changed
New Pay Monthly mobile and mobile broadband contracts on Three are now capped at 100Mbps. To get full network speeds, customers can pay an extra £4 a month as a "Full Speed Add-on". The add-on comes bundled in on Three's Lite+ plans and on some other tiers too, but the inclusion does not follow an obvious pattern, so always check the individual plan details before assuming you need to pay £4 extra for full speeds. The full terms are set out in Three's latest price guides, which were published on 19 April 2026.
Pay As You Go is hit harder, and there is no equivalent £4 add-on to lift the cap. New PAYG mobile customers are capped at 25Mbps as standard, or 50Mbps if they take an Auto Renew Data Pack. PAYG mobile broadband is capped at 50Mbps. Existing PAYG customers who already have an active Auto-renew Data Pack keep their original uncapped speeds, but only while that pack stays active.
The cap is a notable shift. Until last week, Three's marketing made a point of offering uncapped 5G as standard. According to Opensignal's January 2026 UK Mobile Network Experience report, the average 5G download speed on Three was 187Mbps, so the new cap roughly halves the speed most users were getting.
Why Three has done this
In a statement, a VodafoneThree spokesperson said the change is about giving customers more flexibility, describing the new structure as "speed tiers on Three's mobile network, which will enable new and upgrading customers to choose the data speeds which best match their needs." The company points out that 100Mbps is still faster than the UK mobile average, which it cites as 72Mbps based on the Ookla Speedtest Global Index for December 2025.
In practice, the move brings Three into line with Vodafone, which has had similar speed tiers in place for some time. Three and Vodafone merged in 2025, with Vodafone holding 51 per cent of the combined business. We covered the deal at the time in our explainer on the £16.5 billion VodafoneThree merger, which set out what the new joint venture meant for customers. The cap is the first significant consumer-facing change to come out of that merger.
What this means for SIM only buyers
If you are mid-contract on Three, nothing changes. The cap only applies when you upgrade, recontract, or take out a new plan. At that point, the £4 monthly add-on becomes the difference between Three's headline price and what most people would consider the same service Three was selling a fortnight ago. If the cap pushes you to switch network entirely, our guide on keeping your number when switching explains how the PAC code process works.
For anyone shopping for a new SIM only deal on Three's network, Smarty is currently the more interesting option. Smarty is owned by Three but operates on a separate wholesale agreement, and at the time of writing it is not subject to the new caps. That makes it the most direct route to Three's full network speeds without paying the £4 premium. The same applies to iD Mobile, which also runs on Three. Both could change at contract renewal, but for now neither has matched the cap.
Three itself describes 100Mbps as enough for 4K streaming, online gaming and high-quality video calls, while positioning Full Speed as the option for users who binge TV, game online or livestream. The overlap is obvious, and most users on a phone will not notice the difference between the two tiers. The exception is anyone using their phone as a personal hotspot to share data with a laptop or other devices. In that scenario, the cap is more likely to bite, and the £4 add-on starts to look less optional.
Editorial policy
This article is produced by the SIM Only Finder editorial team to help readers understand changes to UK network terms and pricing. Network terms, pricing, and plan availability are checked regularly and updated to reflect current offers. Always confirm current terms directly with the network before signing up.
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