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Three vs O2: comparing 4G/5G network coverage, speeds & benefits

Three vs O2

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Will you get a better 4G/5G signal on O2 or Three? Which has faster speeds? Who has the best roaming? Our comparison reveals the answers. SIM Sherpa is your trusty guide. Last updated: 21st April 2021

What we compare in this guide

Quick update on latest offers

Comparing O2 and Three's networks

Network coverage: do Three or O2 have better signal?

Comparing O2 and Three's 5G, 4G and 3G coverage across the UK

Mobile signal bars with O2 and Three logos

O2's have a better mix of coverage than Three

O2 best network for coverage banner

See network awards

(opens in new window)

Both Three and O2 are mobile networks in their own right, they don't use anyone else's to bring their customers signal. There are strengths and weaknesses to both.

For basic calls and texts, we'd say O2 have the advantage over Three. The amount of the country's physical geography covered is greater and their indoor signal for calls uses naturally better frequencies.

For 4G data (see 5G below) things are much more even. In large towns and cities, there's little to split them. O2 are still probably better in urban locations but Three may have a slight advantage in rural countryside.

A lot of it will come down to which is better in the places you'll use your phone, so make use of their coverage checkers below - and don't just look at home. Think about everywhere you're likely to go regularly.

Useful link: What Three say about their network

5G is live on both O2 and Three

Three's 5G locations map

See all 5G cities

(opens in new window)

If you have a 5G-ready phone, O2 and Three are both suitable choices to make use of it. They both include 5G at no extra cost but be sure to select that your phone is 5G ready with O2 to get the right SIM sent out.

5G coverage on both is still on a city-by-city basis. Rural 5G coverage is rare. And both networks have focused their rollouts on city centres only. So saying a place has 5G doesn't mean the whole place has it.

To compare at a top level, O2 have 5G in these 150+ locations, while on Three it's these 192. There's a bit of overlap between them but if you're desperate for 5G today, check yours is there.

With the rollouts moving so fast, it is difficult to get a guage on which of the two has better 5G coverage. And we'd also say, 4G and 3G are more important for the time being anyway, as you'll spend much more of your time on those than 5G with every network.

Useful link: Latest O2 5G rollout news

Use O2 and Three's coverage checkers

Check at home, your route to work/school and anywhere you'll use your phone

Three's coverage checker

Three coverage checker

Check Three signal

on their official map
(opens in new window)

O2's coverage checker

O2 coverage checker

Check O2 signal

on their official map
(opens in new window)

Our verdict on coverage:

O2 win

"Overall, we still think joining O2 is a better guarantee of having a good signal for calls and data as you travel around. But if you're mostly in big cities, there's little to split them."

Compare pricing and deals

Download speeds: are O2 or Three faster?

Which has faster 4G and 5G data?

O2 and Three logos with a speedometer icon

Three's 4G downloads around 20% faster than O2

Three best network for data banner

See Three's awards

(opens in new window)

While O2 beat Three for how much of the country they bring 4G to, they've achieved this at the expense of download speed. O2 are the slowest network in the UK.

Independent speed testers Opensignal and Speedtest by Ookla take millions of measurements on smartphones on each mobile network and they consistently put Three's 4G ahead of O2's.

O2's were clocked typically between 16.95 - 18.00 Mbps, while Three's averaged 21.60 Mbps. O2's is like copper phoneline based home broadband, while Three's is more like a low-range fibre connection.

The difference isn't huge. And basic users will probably be happy on either. For more demanding usage like HD videos, Three is more suitable and O2 could start to creak a little.

Useful link: Three carry more data than any other network

Three say their 5G will end up the UK's fastest

Three fastest 5G network banner

Read why

(opens in new window)

5G technology has two purposes. Give you more raw speed to do demanding things on your phone like HD video group calls. But it's also way better in busy places where there a lot of people trying to connect at once.

Three have managed to secure more radio spectrum in similar ranges that can be utilised to improve the speed of their 5G. And early testing in London, puts Three at the top of the pile for downloads.

While O2's 5G was measured on average at 130.04 Mbps (peaking at 289.65 Mbps), with Three's measuring at 191.50 Mbps on average (peaking at an eye-opening 362.46 Mbps).

Those are both home fibre optic broadband beating speeds. And the difference between is unlikely to be noticeable in reality, unless you're downloading massive files like Xbox games over a mobile connection.

Useful link: Why Three say theirs is fastest

Our verdict on data speeds:

A win for Three

"You're more likely to receive a faster general 4G service with Three, than O2, even if top speeds do vary place-to-place. And 5G is shaping up the same. If speed's something you care about, the choice is reasonably simple."

Compare pricing and deals

WiFi calling on Three and O2 compared

O2 and Three both offer WiFi calling. We look at which is best

WiFi calling symbol with O2 and Three logos

Three's WiFi calling works well on loads of phones

Three WiFi calling

See Three's scheme

(opens in new window)

The benefits of networks' WiFi calling schemes are that you can make calls (and send texts on some networks) in places where you've got no mobile signal but you do have WiFi.

Everybody on Three automatically gets access to their WiFi calling scheme called 'inTouch', whether you pay monthly or pay as you go, as long as your phone is one of the supported devices listed here.

Three are the most confident network about supporting WiFi calling on Android phones that weren't bought from them, which can be an issue with other providers. iPhones tend to be compatible across the board.

Where Three have the edge over O2 is that inTouch also supports SMS text messages, which is useful now that many services like banks send you confirmation codes via conventional SMS.

Useful link: See full details and supported devices

O2's WiFi calling scheme doesn't support texts

O2 WiFi calling

See O2's scheme

(opens in new window)

The main point of difference between O2's WiFi calling and Three's is that O2's does not support SMS text message over WiFi. O2's indoor signal is likely to be better than Three's though anyway.

You'll only get WiFi calling included if you join on a pay monthly plan. Pay as you go customers don't get the feature. And you have to manually turn it on in your account, which is a bit irritating.

O2 are a little more hesistant to say they'll support Android phones not bought from them - although our test with a manufacturer-bought Samsung did work (see full device list here).

If it works, the basic functionality of O2's WiFi calling is fine. And you can move from WiFi to a 4G calling without the call dropping, which is handy too.

Useful link: Read all benefits and restrictions at

Our verdict on WiFi calling:

Win for Three

"Not only do we think you've got a better chance of Three supporting your phone than O2 but you'll also get the useful advantage of SMS text messaging over WiFi."

Compare pricing and deals

Extra network features: WiFi hotspots on O2 and Three

Do you get more free WiFi access on Three or O2?

WiFi symbol with O2 and Three logos

O2 customers tap into 15,000 free WiFi hotspots across the UK

Free O2 WiFi hotspots

How to connect

(opens in new window)

It's good when a mobile network can give you free access to WiFi when you're out and about because it saves you using up your monthly allowance of mobile data and WiFi can offer a faster connection.

So one handy benefit for O2 customers is getting free access to 15,000 hotspots on the high street (find hotspots near you with O2's map here). You'll also get it on London's TFL network.

These are free for non-O2 customers anyway but the unique perk for O2 customers is that around 4000 of these can be automatically accessed without having to log in.

The hotspots recognise your O2 SIM and will connect you if they can offer a better speed than your current mobile data connection. We've tested it ourselves and it really does work.

Useful link: How free O2 WiFi works

Three's only free WiFi is on the London Underground

Free WiFi on the Underground

How it works

read Three's official guide
(opens in new window)

O2 WiFi hotspots are actually still a free service for anyone, whether you're on O2 or not. The only difference for non-O2 customers is you'll need to login each time you want to access a hotspot.

For that reason, it's difficult to say that O2 has a huge upper hand on Three for free WiFi.

For Londoners, you'll also get free WiFi on the London Underground as a Three customer. That gives you an internet connection at over 250 stations across the network.

You also get this on O2 so it's not unique to Three, meaning there's actually little to split the two networks when it comes to the free WiFi access you get included.

Useful link: How to get free WiFi on the Underground with Three

Our verdict on free WiFi:

Minor win for O2

"Connecting automatically to some O2 WiFi hotspots is a handy little benefit for O2 customers, although we'd probably not make it the crucial deciding factor between the two."

Compare pricing and deals

Comparing perks and benefits on O2 and Three

Inclusive roaming: O2 Travel vs Three Go Roam

Now every network has to offer free EU roaming, we see if inclusive roaming on O2 has caught up with Three

A globe with O2 and Three logos

Roam in 71 countries worldwide at no extra cost with Three

Three Feel At Home roaming

See all countries

(opens in new window)

Now that all networks must offer free EU roaming, the key difference between networks is where else in the world they let you use your minutes, texts and data. And how much that costs.

For us, Three have the better scheme. Better than O2, and better than all the other networks. It's all to do with the number of extra countries, and the amount of plans you get it included with:

Their Go Roam scheme lets you visit any of the 71 countries listed here without paying extra to use your regular UK minutes, texts and data - on every one of their pay monthly phone or SIM only deals.

There are some fair usage limits (read more about them here) mainly on high data usage and living abroad permanently. But for genuine holidays to normally pricey far flung destinations, it's an excellent money saver.

Useful link: See where you can go and full terms and conditions

O2's inclusive worldwide roaming is limited to more-expensive deals

Free O2 EU roaming

See costs per country

in O2's international guide
(opens in new window)

Like all networks, O2 now let you use your regular UK minutes, texts and data within the EU for no extra cost. Join on the right plan, and they offer something that gets close to Three's Go Roam too:

SIM only plans over £20 a month, and most smartphone plans over 4GB (O2 flag which ones), give you free access to O2 Travel Inclusive Zone, which gives you free roaming in these 27 extra non-EU destinations.

Instead of calls, texts and data coming out of your normal plan, O2 give you a daily batch of 120 minutes and 120 texts back to the UK, plus an undetermined amount of data (likely around 100MB or so before being slowed down).

It's less generous than Three's Go Roam and O2 are making you spend extra to get it. If your O2 plan doesn't include it, you can buy daily add-ons or pay as you go (see costs of each here).

Useful link: Learn about free EU roaming and other costs

Our verdict on inclusive roaming

A clear win for Three

"In terms of number of destinations you can visit without paying extra for roaming, Three not only beat O2 but all other mobile networks. Not bad when you consider Three are usually cheaper than other providers too."

Compare pricing and deals

Other added perks on Three vs O2

Some networks now offer free data for streaming, we compare Three and O2

Giftbox with Three and O2 logos

O2 Priority is still the UK's best rewards scheme for mobile customers

O2 Priority rewards scheme

See available deals

(opens in new window)

Their plans might not be the very cheapest around but O2 make up for that in part by giving all 22 million of their customers to the reward scheme O2 Priority. For us, there's no better scheme of this type.

It's basically a bit like a club where high street and online retailers post exclusive offers and discounts that only O2 customers benefit from. That can be on shopping, food, travel and more.

Priority members also get first dibs on tickets where O2 are the venue or event sponsor, plus special treatment while you're at the event itself (here's some examples of what to expect).

If you use Priority correctly for things you were going to pay for anyway, it makes a good way of clawing back some or all of the monthly cost of your phone or SIM deal.

Useful link: See everything you get with Priority in O2's full online guide

O2 offer time-limited free trials with Extras

Extras on O2

See all choices

(opens in new window)

There's no similar unlimited streaming data schemes to Go Binge on O2. But they have recently introduced a new benefit that does get you a free trial to a streaming app.

It's called Extras. And you get it included on selected O2 Refresh phone tariffs or SIM only plans, basically the more-expensive ones (so O2 are using them to persuade you onto higher tariffs).

When you take one of those plans, you can choose to add a free trial lasting up to 6 months of Disney+, Amazon Music, Prime Video or Audible, or any of these other apps.

We'd stress that the services become payable after the free trial, so this isn't O2 being particularly generous. But if you remember to cancel or don't mind paying, it's still a freebie you wouldn't otherwise get.

Useful link: Full O2 Extras FAQs

Three have been stripping out a lot of benefits

Expired stampThree Go Binge streaming

Read more

(opens in new window)

Even though their physical mobile network was the smallest, Three always made up for it with a big package of value-added benefits. Combined with decent prices, we used to give Three our highest review ratings.

But in the last few years, they've retired their O2 Priority rival rewards app Wuntu, removed a free easyJet upgrade perk for their customers and got rid of unlimited streaming data on Netflix.

So now, apart from extra worldwide roaming, the cupboard's looking a bit bare. There are fewer reasons not just to join their low-cost sub-brand SMARTY if you just want a low-frills cheap SIM (apart from they don't have 4G).

Useful link: Read our SMARTY vs Three guide

Our verdict on extra perks

Win for O2

"If you'd asked us two years ago, it'd be a slam dunk for Three. But now they've removed loads of benefits, it's O2 that come out on top in this category."

Compare pricing and deals

Comparing pricing and deals on O2 and Three

SIM only plans: how prices compare on O2 and Three

Are Three's SIMs always cheaper than O2's?

O2 and Three logos with a SIM card



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Added features

SIM only plan prices

A win for Three

"Use the deal finder above and you'll notice Three's SIMs are usually cheaper for the same minutes, texts and data. Keep an eye out for special offers that can even out the playing field from time to time."

Compare pricing and deals

Special offers available on O2 and Three

Here's what promotions Three and O2 have running this month

O2 and Three logos with a special offer ribbon

Phone contracts compared on Three and O2

Are O2 or Three cheaper for taking a pay monthly smartphone deal?

O2 and Three logos with smartphone icon

O2's smartphone contracts are a lot more flexible than Three's

O2 custom plans

See custom plans

(opens in new window)

If you've not heard about them, O2's custom plans are worth a look. These let you pick your own contract length anywhere between 3 and 36 months, plus how much you're willing to pay up front.

The benefit of this is you can pick a deal that matches your monthly budget. If you can afford it, you can choose a shorter term and pay more per month. Or if you want a lower monthly payment, choose a longer contract.

This all works because O2 split their phone contracts into two parts: a loan for the cost of your phone, and a plan for your mins, texts and data.

Changing the contract length keeps the total cost of the phone the same, it's just spread over a different number of months.

The other advantage of having a phone on a credit agreement is that you can upgrade early or leave by paying it all off at once whenever you like. The downside is you're need a good credit rating to be accepted on O2.

Useful link: Use our phone contract comparison tool

Three's phone contracts are generally cheaper than O2 and simpler

Compare phone contract prices

Use phone deal finder

(opens in new window)

With Three, there's not as much flexibility as on O2 with your phone contract. They offer what we'd call regular 24-month mobile contracts, where the cost of the phone, your minutes, texts and data, are all bundled into one single payment.

This means it's a lot simpler to compare prices and choose the right deal. It could also mean it's easier to get accepted for a deal with Three, because there's no finance involved (note: we have no specific info on Three or O2's credit policy).

Generally, we'd say Three will work out cheaper than O2 but it will all come down to what deals are live at the time that you buy. Use our comparison tool to compare.

Useful link: Use our phone contract comparison tool

Our verdict on phone contract prices:

Three marginally cheaper

"We can say Three are cheaper on average than O2 but the smart thing to do is use our comparison tool to look at precise costs for the mins, texs and data you want."

Compare phone prices

More guides about Three

Other O2 guides