If you’ve got a fast connection you want to use it – so why let a data cap hold you back? Today’s smartphones are built for streaming video and music, or even online games, but using these services can punch a big hole in your monthly data allowance, or even push you into expensive extra charges. Throw in new phones, 5G networks and new applications, like game streaming, and the problem will only get worse.

The answer is an unlimited data plan, giving you all the data you can use for a reasonable monthly fee. Not every mobile network offers them – and you’ll find some have their hidden gotchas – but if you want to use your phone or tablet with data-heavy streaming services, you’ll find them well worth looking out for.

What should you look for in an unlimited data plan?

Unlimited data is the obvious answer, but you can also expect unlimited calls and texts on top. Some services may also bundle additional features. For example, EE will sell you unlimited packages with up to two of its swappable benefits included, while Three throws in its Go Binge and Go Roam around the World features.

Is it really unlimited?

For most practical purposes, yes, but watch out for the terms and conditions. Both Three and EE, for example, insist that their unlimited tariff really is unlimited, with no restrictions bar the usual ones about illegal or commercial use.

However, EE has a fair usage policy where usage above 1,000GB per month is considered commercial use, while tethering 12 more devices is a no-no. O2 has a similar fair usage policy, under the terms of which it will monitor your use and, if you regularly tether 12 or more devices or use 650GB of data twice in a six month period, it may investigate whether this is outside permitted use.

Of course, you’d have to be going some to trigger these restrictions, but it’s worth bearing in mind if, say, you decided to pop an unlimited data SIM inside a 4G router.

Giffgaff’s Always On goodybag gives you unlimited data, but only the first 40GB per month at full 4G speeds. After that, you’re reduced to a rather miserable 384kbits/sec between 8am and midnight. That’s technically Always On, but not what you might call unlimited.

The other thing to watch out for is international roaming. With most suppliers you’ll find that unlimited only applies within the UK, and that you still have a data cap while abroad. With Three, for instance, this is 15GB within Europe and 12GB further afield, so you still have to be careful while you’re on your hols.

Read next: The best SIM-only deals

The best unlimited data plans

1. Three: The best value unlimited data plan

Price: From £20 a month | Buy now from Three

At just £20 a month, Three’s Unlimited 24-month advanced plan is fantastic value – and at the time of writing you can have it half-price for the first six months. It includes unlimited minutes, texts and the Personal Hotspot tethering feature, along with Go Roam Around the World, allowing you to use 15GB of your allowance within the EU and 12GB in a total of 71 destinations, including Hong Kong, Singapore, the US, Vietnam and Australia.

The inclusion of Go Binge – where data used with many streaming websites doesn’t make a dent on your monthly allowance – seems peculiar on an unlimited contract, but at least there are no hidden caps or restrictions inside the UK. What’s more, your plan is 5G ready once Three’s 5G services reach you and you buy a 5G phone. In fact, this might fix Three’s only problems; the most recent RootMetrics performance tests saw it languishing behind EE and Vodafone in terms of average connection speeds. If you can cope with this and the two-year commitment, you won’t find a better bargain in SIM-only plans – and you can cut that back to a year for just £2 a month extra.

Key specs - Network type: Primary network operator; Contract length: 12 months (£22), 24 months (£20); Additional features: Go Binge, Personal Hotspot, Go Roam Around the World.

Buy now from Three

2. EE: The best unlimited data plan for speed and sharing

Price: From £34 a month | Buy now from EE

EE’s Unlimited plans start at £34 for a 4G SIM with an additional £10 if you want to go 5G, so it’s not the cheapest option out there. It does, however, have a few points in its favour. First, you can use your full plan allowance of minutes, texts and data inside EE’s Europe Zone. For another, you can have multiple family members using different plans on one joint account, and gift them up to 120GB of your data allowance from your Unlimited plan; not bad if you’ve got a data-hungry household.

We’re not convinced that EE’s swappable benefits are worth the £5 extra you’ll pay over the basic plan, unless you want to travel in the countries listed for EE’s Roam Further Pass (including the USA, Australia, Canada and New Zealand) or fancy an Amazon Prime Video membership without an Amazon Prime subscription. But then the best reason to go for EE for unlimited data is that it’s comfortably the best network for speed and coverage, having dominated RootMetrics’ speed tests five years in a row. Want the fastest, unlimited mobile connection? EE is the network to choose.

Key specs - Network type: Primary network operator; Contract length: 12 months (£34 to £44); Additional features: 120GB data sharing on joint accounts, Swappable benefits on premium 12-month SIMs.

Buy now from EE

3. iD Mobile: the best unlimited data plan for short-term contracts

Price: From £23 a month | Buy now from iD

What if you want unlimited data without the commitment of a lengthy annual contract? That’s where iD Mobile’s Unlimited Data plan comes in. For £25 a month you can have unlimited minutes, texts and data, but on a 30 day rolling plan. Need unlimited data in the summer but not in the winter when you’re stuck indoors? You can flex the plan up and down. This makes iD an attractive option if you don’t need unlimited data month in, month out.

iD Mobile has a fair usage policy with regards to roaming, which kicks in if you spend more time abroad than at home, but it doesn’t have one as far as data usage goes. This means you won’t have to watch your use in fear of triggering speed restrictions, as you will with iD’s arch-rival Giffgaff and its equivalent Always On data plan.

iD is a virtual network operator running on top of Three’s network, so the same concerns about speed apply. In practice, you’re unlikely to find connections slow, but if you want the fastest possible connection, then look to Vodafone or EE. Otherwise, while Three is cheaper on its two-year contract, iD is better if you don’t like to be tied down.

Key specs - Network type: Virtual network operator; Contract length: 30 days; Additional features: None.

Buy now from iD

4. Vodafone: the best unlimited data plan for video streaming

Price: From £36 a month | Buy now from Vodafone

Vodafone has some superb 4G and 5G unlimited plans, but you have to be wary of a few potential gotchas. It’s cheapest unlimited package, Unlimited Lite, costs £23 but has a 2Mbits/sec maximum download speed – which kind of misses the whole point of unlimited and/or 5G. The £26 straight Unlimited plan isn’t much better, with a 10Mbits/sec speed restriction. It’s only when you get to the £30 a month Unlimited Max packages that you get maximum speed and unlimited data.

In most respects, it’s still a bit middle-of-the-road; more expensive than Three and ID’s unlimited options but without the high performance of EE, though you can have Unlimited Max on a more flexible 30-day contract. However, Vodafone has pushed ahead of Three on average speeds to come into second place behind EE for performance, according to the latest RootMetrics survey. What’s more, Vodafone has some tempting entertainment options. Get Unlimited Max with Entertainment and you can have a choice of streaming services over the 12-month contract period, including Amazon Prime Video, Spotify, NowTV’s Entertainment pass and Sky Sports Mobile. In a way, you’re getting all the data you need for streaming plus something worth using it for in one handy bundle.

Key specs - Network type: Primary network operator; Contract length: 30 days to 18 months; Additional features: 77 roam-free destinations, three-month trial of Secure Net, choice of entertainment on Unlimited with Entertainment plans.

Buy now from Vodafone

5. O2: the best unlimited data plan for offers

Price: From £33 a month | Buy now from O2

O2 has a choice of 4G or 5G data plans at £33 a month on an 18-month contract, making it slightly more expensive than Vodafone but a little cheaper than EE. As with Vodafone, it’s the features that make the plans interesting, with six months of Amazon Prime Video, Amazon Music Unlimited or Audible currently being thrown in, plus O2’s usual free Wi-Fi, Travel Inclusive Zone and Priority offers. These give you money-off deals on restaurants, early booking for O2 venues and the ability to use your monthly allowances in some key destinations outside the EU, including the US, Canada, Australia and a sizable portion of Central and South America.

For some, this could make up for the fact that O2 isn’t particularly fast. In the last RootMetrics tests the network was still trailing EE, Vodafone and Three for average speeds and coverage, though it has seen improvements in the last two years. The situation might change as 5G rolls out to more areas, but right now you come to O2 for the extras, rather than world-beating performance or low prices.

Key specs - Network type: Primary network operator; Contract length: 30 days to 18 months; Additional features: Daily offers with Priority, free O2 Wi-FI, O2 Travel Inclusive Zone.

Buy now from O2