SMARTY's unlimited data SIM for £17: is it truly unlimited?

We don’t think there’s a more flexible unlimited data plan on the market than SMARTY’s. There’s no contract, just a rolling 1-month plan that you can cancel or change anytime.

You’re also free to use the SIM in phones, tablets or mobile broadband routers. As long as it’s for personal use, you’re not restricted by speed caps or usage limits.

And our exclusive hidden offer at £17 a month saves you £3 vs the full £20 price SMARTY advertise on the main part of their website:

Unlimited minutes + Unlimited texts + 0MB Unlimited data (5G) = £20 £17 a month (1‑month plan, no contract)
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🛈 Price stays £17 while you keep renewing

One of the things we rate most about SMARTY’s unlimited data SIM is how flexible it is compared to others. First, it’s a rolling monthly plan. That means there are no contracts, no notice periods and no commitment.

You pay up front each month and can stop it whenever you like. That’s perfect if you want to test out SMARTY or the Three network, without being locked in. Other contract-based 1-month SIMs require you to give notice to leave.

The data itself is truly unlimited for use in the UK. There are no speed caps, throttling, no data limits or hidden fair usage policies. You’re also free to tether as much as you want or use the SIM in tablets, dongles or mobile broadband devices.

Other 1-month unlimited data plans

Overall, we’d say there’s no other 1-month unlimited data SIM this flexible. And at just £17 a month, you’d be hard fought to beat it even on a longer contract.

SMARTY use Three’s network, so you get the same underlying 4G and 5G coverage. But there is now one important difference: SMARTY do not cap your speeds (Three limit their standard plans to 100 Mbps).

SMARTY estimate maximum 5G downloads of 597 Mbps. Independent network testers Opensignal measured average 5G downloads of 187 Mbps on Three’s network in their latest report.

That means SMARTY can let you go faster than Three’s own ordinary plans whenever the local network can deliver it. Three customers need a pay extra to upgrade to full speeds.

If you want to use unlimited data for large downloads or tethering other devices, getting the network’s full available speeds without paying for an add-on is a genuine advantage to SMARTY.

SMARTY’s unlimited data really is unlimited for personal use within the UK. There are no speed caps, and you’re free to tether or use the SIM in tablets or mobile broadband devices.

And you can only use the plan for personal, non-commercial purposes. So you cannot use it to provide a public WiFi service or run connectivity for a business.

In the background, we think there is a soft limit of 1000GB where SMARTY will investigate how you’re using your SIM. It’s not a cap, just a red flag to them that you may be using it for other purposes.

You can use the SIM in your phone, tether other devices or put it in a tablet, dongle or mobile broadband router.

Also, when you’re roaming within the EU there is a 12GB monthly fair use limit. That’s lower than it used to be but still enough for typical short trips. Once you hit that, you’ll need to buy a data add-on if you want to continue using mobile internet abroad.

SMARTY’s unlimited deal is almost always among the best priced on the market, particularly when you look at 1-month plans. Sometimes, longer contracts do minorly win out. Here’s the latest comparison: