Sky Mobile and giffgaff both run on O2's network, so they get the same coverage wherever you are. Ofcom lists both among the brands that "use O2's network". They take very different routes to it, though. Sky Mobile is part of Sky and sells 12-month plans with data rollover. giffgaff is owned by Virgin Media O2 and sells rolling plans or 18-month contracts with a price lock. The right one depends on how you use data, how long you want to commit, and how you like to get help.
How do Sky Mobile and giffgaff compare at a glance?
The table pulls prices and price rises from our live deal feed, so it matches the deals on our comparison pages today. The roaming, eSIM and exit-fee rows come from each network's own pages.
| Feature |  Sky Mobile |  giffgaff |
|---|---|---|
| Owned by | Sky | Virgin Media O2 |
| Runs on | O2's network | O2's network |
| SIM only from | £4 a month | £6 a month |
| Cheapest unlimited data | £18 a month | £14 a month |
| Capped data plans | 3GB to 75GB, plus unlimited | 2GB to 200GB, plus unlimited |
| Contracts in our deals | 12 months | 30-day and 18 months |
| Scheduled price rises | None scheduled. Its terms say: "Price could change during your contract" | None scheduled on current deals |
| EU roaming | £2 a day. Roaming Passport Plus covers 120 destinations worldwide; 25GB fair use. | Included. Up to 5GB, with top-up add-ons after that. |
| eSIM | Yes. Chosen at order; replacing an active eSIM means calling Sky. | Yes. Activation is app-only; there are no QR codes. |
| Leaving early | A set amount per plan for the months left, from Sky's published table. | Monthly plans: nothing. 18-month plans: half the monthly price for each month left. |
| Deals | See Sky Mobile deals | See giffgaff deals |
Live rows show the deals in our feed at the last refresh, not every plan a network sells. EU roaming was checked against each network’s own pages on 28 August 2026, eSIM on 26 August 2026, and ownership and exit terms on 23 September 2026.
Which is cheaper, Sky Mobile or giffgaff?
It depends on the allowance, and the gap is often small. When we checked on 23 September 2026, both sold 40GB of data for £8 a month, Sky on a 12-month term and giffgaff on an 18-month one. For unlimited data, giffgaff was £14 a month on 18 months and Sky was £18 a month on 12 months.
The term lengths change the comparison. Sky's unlimited plan costs £216 over its 12 months, and giffgaff's costs £252 over 18. Per month giffgaff is cheaper, but you commit for half a year longer. giffgaff also sells rolling monthly plans with no commitment, at £20 a month for unlimited data when we checked. Sky doesn't sell a rolling SIM in our feed.
So if you know you'll stay for a year and a half, giffgaff's contract is the lower monthly price. If a year is your limit, Sky's term is shorter. Our data allowance guide helps you pick the right size before you compare.
Can either put the price up?
Neither has a scheduled rise in our feed, but they word their promises differently. giffgaff's deals page offers a "Price lock" with "no mid-contract price rises" on its 18-month contracts. Its general terms still keep the right to change prices with advance notice.
Sky's plans page says the "data plan price may change during the 12-month minimum term". Because no amount is agreed up front, a Sky rise comes with 30 days' notice and the right to leave without penalty, as our price rise guide explains.
giffgaff's promise is the stronger commitment on paper. Sky's shorter term and exit right limit how long any rise could affect you.
What happens to data you don't use?
Sky's plans page lets you "roll your spare data for up to a year". You can also spend spare data "on a range of rewards" instead. On a capped plan, that builds a buffer for months when you use more than usual.
giffgaff doesn't advertise rollover on its SIM plans. Its approach is flexibility instead: on an 18-month contract you can move up or down a plan each month without restarting the term. Sky lets you "change your data plan whenever you like" too, so both let you adjust as you go.
If your usage swings a lot, Sky's rollover smooths it out. If it's steady, the flexibility to change plan matters more than rollover.
Which is better for using your phone abroad?
For trips within the EU, giffgaff includes roaming up to 5GB a month and then charges 10p for each extra MB, according to its plan pages. Sky charges £2 a day through Roaming Passport Plus, which covers over 120 destinations worldwide.
For a week in Europe using under 5GB, giffgaff costs nothing extra and Sky costs £14. Further afield, Sky's pass covers destinations outside the EU at the same daily price. Our EU roaming guide compares every network's charges.
Will either run a credit check?
giffgaff doesn't for SIM plans, including its 18-month contracts. Its help pages say: "They'll only carry out a credit check if you buy a phone on a contract with a loan". Sky Mobile's plans are a 12-month contract, so check Sky's terms at sign-up if a credit check concerns you.
How does customer service compare?
The two work very differently. giffgaff has no phone line; help comes through its online help hub, an AI assistant that passes you to human agents, and its member community forum. Sky Mobile has phone support, and its shop page promises switching help run by real people, 24 hours a day.
On Ofcom's measures, giffgaff scores higher. Ofcom recorded 1 complaint per 100,000 giffgaff customers from January to March 2026, and 4 for Sky Mobile, against an industry average of 2. In Ofcom's 2024 customer service survey, 94% of giffgaff customers were satisfied overall, compared with 87% at Sky and an 88% average.
If you want to speak to someone, Sky offers that, and its average call wait in the survey was 1 minute 12 seconds. If you're happy online, giffgaff's scores show its model works well for most members.
What extras come with each?
giffgaff runs Payback, which pays members for recommending friends, answering community questions and suggesting ideas. Each point is worth 1p, paid out in June and December as PayPal cash, credit or a charity donation. It's also a certified B Corp.
Sky's extras connect to the wider Sky account. Customers can use Sky VIP, the loyalty scheme across Sky's TV, broadband and mobile. If you already pay Sky for TV or broadband, adding mobile keeps things with one provider.
Why you might choose Sky Mobile
- You want data rollover on a capped plan.
- You'd prefer a 12-month commitment to an 18-month one.
- You travel outside the EU and want one daily price in over 120 destinations.
- You want phone support, or you're already a Sky customer.
Why you might choose giffgaff
- You want the lowest monthly price for unlimited data and can commit for 18 months.
- You want a written price lock, or a rolling plan with no commitment.
- You travel in the EU and use under 5GB while away.
- You'd rather avoid a credit check, and you're happy to get help online.
How do you switch between Sky Mobile and giffgaff?
Your signal stays the same, since both use O2's masts. Text PAC to 65075 from your current phone and the code arrives within a minute. Give it to your new network and the switch completes within one working day, under Ofcom's rules. Our switching guide covers each step.
Leaving mid-term costs money on both. giffgaff charges half the monthly price for each month left on an 18-month plan. Sky uses a published table for each plan. Our guide to leaving early covers both formulas.
Sources and how we checked
Prices, contract lengths and scheduled rises come from our live deal feed and refresh whenever the site updates. We checked Sky's mobile plans page and giffgaff's SIM deals page, terms and conditions and credit check help on 23 September 2026. Service figures come from Ofcom's telecoms complaints data and Comparing Customer Service report.