Sky Mobile vs O2:
key differences between the 4G/5G networks

✔ 4G, 3G and 2G is identical on Sky Mobile and O2

Sky Mobile are fairly obviously owned by Sky. While O2 are owned by a company called Telefonica. Sky Mobile have always used O2's network and have just signed a long-term deal to use them in future too.

Sky Mobile customers get full access to identical 4G, 3G and 2G coverage to being on O2 directly. So if you've been with O2 before, you shouldn't notice a diffference swapping to Sky Mobile.

If you've been with neither before, you can look forward to 98% 4G population coverage (signal in the places people live). And we estimate they've got the joint-second largest amount of the UK's landmass covered too.

But we still recommend using either networks' coverage checkers below to test signal away from where you live. Think about your route to work/school or places you regularly travel to away from large towns.

Useful link: Which network has the best indoor signal?

✔ Both providers now have 5G in the same locations

If you're an early adopter, the good news is that O2 and Sky Mobile now both have 5G switched on, ready to use. Like with 2G/3G/4G, Sky and O2 have 5G in the exact-same locations (23 and growing).

5G on all networks is still in the very early stages. When providers say they have 5G in a city, it still means select locations within that place (use their 5G coverage checkers for a street-by-street view).

O2 and Sky's best-value 5G SIMs

We'd say neither O2 or Sky are offering 5G on a totally free basis. On O2, it's only select tariffs that have 5G data. On Sky, you either pay for a 5G add-on or get it free by joining Sky VIP.

Useful link: News on Sky Mobile's 5G launch

✔ Get the same 4G speeds on Sky Mobile as O2

Independent mobile network testers Opensignal and Speedtest by Ookla put O2 as having the slowest typical 4G download speeds among the UK's four mobile networks at between 15.8 Mbps and 16.95 Mbps.

Although you probably wouldn't notice the difference between this and faster networks on everyday internet browsing, things like large downloads and ultra high definition streaming might be less seamless.

There's no speed cap on Sky Mobile vs being on O2 directly, so we're confident there's no speed differences between joining either network - so this needn't be something to use to decide between them.

4G speed is the only real weakness we'd point out in this entire section about what each provider's mobile network is capable of.

Useful link: More about O2's 4G

✔ O2 have WiFi calling, 4G calling and free hotspots

O2 (and therefore Sky) use some of the best frequency mobile signal for getting into buildings to make calls. But even so they still have a couple of backups too: WiFi calling and 4G calling.

WiFi calling lets your phone make/take calls over WiFi wherever there's no mobile signal. And 4G calling lets your phone use 4G for calls, instead of just 2G/3G, meaning better coverage and higher quality audio.

That's great if it all works but we don't rate O2's WiFi calling as highly as others, as it doesn't support SMS text messaging, you only get it on pay monthly and there are issues around whether O2 will support your phone.

One nice extra network feature on O2 is that you'll get free automatic access to O2 WiFi hotspots around the country. These save your mobile data allowance and might get you a faster connection than 3G/4G.

Useful link: O2's guide to all their network features

✔ Sky Mobile have WiFi calling and some free hotspots

Like O2, Sky Mobile also offer WiFi calling with their pay monthly plans. And like O2, there's quite a few compatibility issues with Android phones (iPhones should be ok).

If didn't buy your Android phone from Sky, with their software pre-installed, they don't guarantee it will work (our tests confirmed that WiFi calling did not work on an Android phone bought elsewhere).

We also couldn't get 4G Calling (VoLTE) to work on Sky Mobile on either an Android or iPhone model. So that's a difference between O2 and Sky.

Like O2, you'll get free access to Sky WiFi hotspots around the country (these are free to anyone already though). But you won't get free WiFi on London's TFL network like you do on O2.

Useful link: Full help guide on Sky's WiFi calling

✔ Sky Mobile customers get free data to stream Sky TV apps

For us, the very best benefit about joining Sky Mobile is that you'll get unlimited streaming data to watch Sky's TV apps with every single plan for free. Watch as much as you like, it won't come out of your mobile data.

Streaming just a one-hour long episode of a programme could use around 1GB data, so it's a really valuable benefit for anyone who's got a Sky TV package and want to watch it while you're out of the house.

It comes even on the very cheapest SIM only plans with only 1GB/2GB themselves (typically around £6 a month). So it's an incredibly generous offer from Sky.

It only works with Sky TV apps. No other services are included (see Three's Go Binge for free Netflix and Apple Music data). But if you have Sky TV, it's a strong incentive to join them for mobile.

Useful link: Sky's full guide to free streaming data

✔ O2 have unlimited data plans as an option

There's nothing similar to Sky's streaming benefit on O2 (see our guide to all other networks with free data for streaming or social media schemes here). But it is possible to buy unlimited data for any use.

You can get it on select O2 top-end model phone contracts. Or on SIM only there's a couple of unlimited data plans:

Sky don't currently do anything similar, although all these networks do offer unlimited data too.

Useful link: O2's guide to their unlimited data tariffs

✔ O2 offer some worldwide inclusive roaming

As a minimum on O2, every pay monthly phone or SIM only contract includes inclusive EU roaming, where you can use your plan's minutes, texts and data in these countries for no extra cost.

But there are also options to get inclusive roaming in worldwide destinations outside of Europe. Either choose a plan with that includes the O2 Travel Inclusive Zone or buy a daily pass while you're abroad (see latest costs here).

Then when you're in one of the 27 extra worldwide countries included in O2 Travel, you'll get a daily allowance of 120 minutes and 120 texts back to the UK and a lean 150MB of data at full speed - after which O2 slow you right down to constrain your usage.

We think that should cover most people's basics while they're away on a temporary trip, although it doesn't go as far as the winners of our best mobile network for roaming rankings.

Useful link: All other roaming costs on O2

✔ Sky only really offer inclusive EU roaming

If you're going abroad to any EU country, you'll be able to use your plan's regular minutes, texts and data at no extra cost - you can use your entire data allowance there. That's all pretty standard.

Sky Mobile don't really have any other form of inclusive worldwide roaming included as part of their plans. If you want to go elsewhere, you're looking at paying extra.

That will either be via Sky's Roaming Passport Plus, which lets you use your plan's minutes, texts and data for a fixed daily cost in certain countries including the USA (see latest costs and destinations here). Or you can pay as you go anywhere else in the world.

Either option can quite quickly add up to large extra bills, so if you're a regular traveller outside the EU, take a look at the networks in our best free roaming guide here to save on costs.

Useful link: Sky's full guide to roaming on their network

✔ Sky Mobile let you keep data longer than anyone else

Whether you take a phone contract or a SIM only plan from Sky Mobile, you'll get their Roll benefit included as standard. This lets you keep data you don't get through for up to 3 years - to use later or share with others.

Each month, they'll total up what you've not used and move it to your Piggybank (like a savings account for data). Then if you ever run out one month, you just take data out again 1GB at a time.

There are also two added benefits. If you've got multiple Sky Mobile deals on your same account for friends and family, you can transfer data over to them. You can also exchange it for discounts off phones and tablets.

Out of all the data rollover schemes in the UK, we rate Sky's as the best one where you keep your data, simply because they let you keep it the longest. We do like SMARTY's system of paying you back the cost of the data in pounds and pence more though.

Useful link: Sky's help article about data rollover

✔ O2 only really offer data rollover on Pay As You Go

You can't get a pay monthly plan with data rollover on O2. But if you ever have to buy more data because you run out, they will let you keep anything from that extra block for later.

The only plans O2 sell with data rollover as standard are their Pay As You Go Big Bundles. These are bundles of minutes, texts and data you buy out of credit you've topped up with.

Generally speaking, these bundles are worse value per minute, text and data than O2's pay monthly plans. But they do have more flexibility, as you've got no contract and you change, stop or pause bundles as you please.

Useful link: See latest O2 Big Bundle prices

✔ O2's phone contracts are among the most flexible

When you take out a phone contract on O2 directly, most models are offered on their Refresh tariffs, which split your deal into a credit agreement (loan) for the cost of the phone, and a monthly usage tariff for your minutes, texts and data.

This gives you the benefit of being able to upgrade early by paying off whatever's left of the cost of your phone (the balance of your loan), without having to pay any other fees for the minutes, texts and data.

O2 have now added more flexibility too through their Custom Plans. These let you choose a contract length anywhere between 3 and 36 months and how much you're willing to pay up front - all without changing the total you pay for the phone.

The benefit of that is you can play with the amounts to get a monthly and upfront payment you're happy with. The downside is, there's now thousands of combinations to choose from.

Useful link: Read O2's guide to their Custom Plans

✔ Sky's phone contracts are based on finance too

Sky also split your phone contract into two parts: a finance agreement for the phone, and a usage plan for your minutes, texts and data. You can choose two contract lengths: 24 months and 36 months.

24-month contracts spread the cost of the phone over a shorter time, so cost more per month but less overall. 36-month ones cost less per month but more overall.

Sky are keen to push their Swap benefit on phones. It's a scheme that lets you "upgrade for free" after 12 months on Swap12 (24-month contract) or 24 months on Swap24 (36-month contract).

We'd recommend not bothering with the early upgrade element of the contracts, because it involves giving Sky back the phone you've been paying off for up to 24 months - it's like selling your phone below its value.

Useful link: Full ins and outs of Sky's Swap