Is Unlimited Data Really Unlimited?

Most unlimited data plans in the UK are genuinely unlimited in the sense that your data will not cut off or incur extra charges when you use a lot. However, networks can apply fair usage policies that allow them to reduce your speeds if your usage is considered excessive. This guide explains how fair usage policies work, which networks apply them, and what the limits are, and was last reviewed in June 2026.

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Reviewed by: Phil Brown, 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. About the author

Last reviewed: June 2026. Updated regularly to reflect current plan pricing, network changes, and roaming policies.

How we put this guide together

To put this guide together, we reviewed the unlimited data fair usage terms published by each major UK network and MVNO, checking the stated monthly thresholds, any speed restrictions, and tethering rules directly against each network's published terms. Where relevant, we have drawn on our own experience of running unlimited plans and using them to tether other devices. Average usage figures reference Ofcom data.

What is a fair usage policy?

A fair usage policy (FUP) sets a threshold for what a network considers reasonable monthly data consumption. If you exceed that threshold, the network may reduce your connection speeds for the rest of the billing period. Your data does not stop working, but it may become noticeably slower.

Fair usage policies are permitted under Ofcom rules, provided they are clearly stated in a network's terms and conditions and are reasonable in their application. They are primarily aimed at preventing a small number of users from consuming extremely large volumes of data in ways that affect network performance for everyone else. For the vast majority of users, fair usage thresholds are high enough that they will never come close to triggering them.

Which networks have fair usage policies on unlimited data?

The following networks apply a stated fair usage threshold on their unlimited data plans. Always check the current terms on the network's website before signing up, as these figures can change:

• EE: 600GB per month. Exceeding this twice within six months may result in speed restrictions or a transfer to a different plan.
• Giffgaff: 650GB per month. Exceeding this twice within six months may result in speed restrictions or additional charges.
• Honest Mobile: speeds reduced to 3G if you use over 750GB in a billing cycle.
• O2: 650GB per month. Exceeding this twice within six months may result in speed restrictions or a transfer to a different plan.
• Lycamobile: 450GB per month. Exceeding this twice within six months may result in speed restrictions.
• Vodafone: 600GB per month. Exceeding this twice within six months may result in investigation and possible transfer to a different plan. Vodafone also sells unlimited at three tiers, Unlimited Lite, Unlimited and Unlimited Max, where the Lite and standard tiers carry a built-in speed cap (2Mbps and 10Mbps respectively) regardless of how much data you use, while Max is uncapped.
• Tesco Mobile: no specific data cap stated, but excessive use that affects other customers may result in a warning, speed restrictions, or suspension.

The following networks do not currently state a specific fair usage threshold on their unlimited data plans:

• Asda Mobile
• iD Mobile
• Lebara
• Sky Mobile
• Smarty
• Spusu: no fair usage policy on its unlimited plans, provided the SIM is used for personal use within the UK.
• Talkmobile
• Three: no stated fair usage policy on unlimited data plans. Three continues to sell plans under its own brand following the completion of its merger with Vodafone in May 2025.
• Voxi

Several of the networks above run on the merged Vodafone and Three network, where post-merger terms are still being aligned. Check the current terms with each network directly before signing up. Note also that even networks without a stated threshold reserve the right to take action against usage they consider abusive or that negatively affects the network for other customers.

What counts as excessive data usage?

Fair usage policies are generally aimed at preventing a small minority of users from using a mobile unlimited plan as a home broadband substitute or running data-intensive servers. Streaming video, browsing, video calls, social media, and general everyday smartphone use will not come close to triggering fair usage thresholds on any UK network. The thresholds are set at hundreds of gigabytes per month precisely because they are not meant to affect normal usage.

Can I tether with an unlimited data SIM?

Yes. Tethering, which means using your phone as a mobile hotspot to share your data connection with a laptop, tablet, or other device, is permitted across all the major UK networks covered in this guide, including EE, O2, Vodafone, Three, iD Mobile, Smarty, Voxi, Giffgaff, Tesco Mobile, Sky Mobile, Lycamobile, Lebara, Talkmobile, Spusu, and Asda Mobile. There are no longer separate tethering charges or additional allowances required. Data used while tethering comes from the same pool as everything else on your plan.

That said, tethering is the activity most likely to push your usage toward a fair usage threshold. Streaming video, downloading large files, or running video calls through a tethered laptop will consume significantly more data than typical smartphone use. Networks that publish a specific threshold, such as EE at 600GB per month or Giffgaff at 650GB per month, apply those limits to all data use including tethering. Networks without a published threshold still reserve the right to act on usage they consider excessive or that negatively affects other customers.

All plans are for personal use only. Using a SIM as a permanent fixed broadband substitute, particularly in a router that runs continuously, sits in a grey area on most networks and is worth checking against your specific network's terms before doing so.

Does unlimited data include roaming?

Not in full. Your unlimited allowance applies to UK use, but most plans still let you use a capped portion of your data when you travel abroad, rather than the full unlimited amount. That roaming allowance and its fair use limit are set separately from your domestic plan.

Most UK networks include EU roaming on their plans, but cap how much data you can use abroad each month. This cap is separate from your domestic unlimited allowance, and the amount varies by network, commonly somewhere between around 12GB and 25GB a month. Always check the specific terms of the plan you are considering before travelling. For more detail on how roaming works, see our guide to EU roaming fees.

Do I need unlimited data?

According to Ofcom's Communications Market Report 2025, the average UK mobile user got through around 10.6GB of data a month in 2024. If your usage is around this level or below, an unlimited plan is unlikely to represent the best value. A capped plan at a lower monthly cost will often work out cheaper overall, and a smaller plan is also less exposed to mid-contract price rises where the increase is applied as a percentage.

Unlimited data makes sense if you regularly stream video on mobile, use your phone as a hotspot for other devices, or work remotely without consistent Wi-Fi access. If you are not sure how much you will use, a 30 day rolling unlimited deal lets you try one for a month without committing. You can compare current unlimited data SIM only deals on our deals page, where results are sorted by monthly cost.

How to check how much data you use

Before deciding whether you need unlimited, check your recent usage so the choice is based on your own numbers rather than a guess. Your network's app or online account will show your monthly data use, usually broken down by billing period. On an iPhone, you can also see a running total under Settings, then Mobile Data. On an Android phone, it is under Settings, then Network and internet, then the data usage menu. Look at two or three recent months rather than one, as a single heavy month is not a reliable guide. If your typical use sits comfortably below a large capped allowance, you are unlikely to need unlimited.

FAQs

Will my data actually stop if I exceed the fair usage limit?

No. Exceeding a fair usage threshold typically results in reduced speeds for the remainder of your billing period, not a complete cut-off. Your data continues to work, but may feel noticeably slower for heavy tasks like video streaming.

Are fair usage limits applied automatically?

Yes. Speed reductions are applied automatically by the network once the threshold is crossed. You do not usually receive a warning in advance, though your network may contact you if you exceed the limit repeatedly.

Where can I compare unlimited data deals?

You can compare all current unlimited data SIM only deals on our deals page, sorted by monthly cost and filterable by network.

Conclusion

For almost everyone, unlimited data in the UK is unlimited in every way that matters: your data will not be cut off and you will not face surprise charges. Fair usage thresholds exist, but they are set so high that only a very small number of heavy users, usually those tethering constantly, will ever reach them. Decide based on your own typical usage, and if a large capped plan covers it for less, that is often the better buy. When you are ready, compare current unlimited data SIM only deals sorted by monthly cost.

Editorial policy

Fair usage policy figures in this guide are based on published network terms and are reviewed regularly. Network policies can change, so always check the current terms directly with your chosen network before signing up.