Mobile Wi-Fi, also known as MiFi, uses your smartphone's mobile data connection to establish a wireless signal that compatible devices can share to get online. It's particularly handy when you are travelling and not within range of a standard Wi-Fi connection, or as a failsafe for flaky or overloaded home broadband.
A mobile Wi-Fi connection can be created by the smartphone itself, using a process known as internet tethering, or by a portable device called a mobile router or a mobile hotspot, into which you insert a SIM card.
When used frequently, mobile Wi-Fi routers can be the preferred solution because they won't drain your smartphone's battery, there's no fiddling around with swapping SIM cards, and you won't need to leave your phone with whomever is sharing its internet connection. They can also be used with data-only SIMs (those that do not offer calls and texts), which can make it cheaper to get online.
The difference between a mobile Wi-Fi router and a mobile data dongle is that it does not physically connect to your device, and it can share a mobile data connection with more than one device. These days, USB dongles are really useful only for devices such as old laptops and PCs that do not support Wi-Fi connectivity.
You can connect multiple devices: Some MiFi devices let you connect 10 or more devices to a single hotspot, which will work out a lot cheaper than paying for a mobile data plan for each of those devices.
You can connect Wi-Fi-only devices to a mobile data connection: Tablets are great to use at home, but what about on the train, on the beach or by the pool? Wherever you can get a phone signal, you can use MiFi to create a wireless network and get online from any Wi-Fi device.
You can save money on your next tablet: Buying a tablet with a 4G or 5G data connection adds around £100 to the price, and that's before you consider the monthly fee for your data. Use some of that money to buy a MiFi router instead and you'll never need to buy a cellular tablet again.
You can reduce roaming charges: Most mobile operators offer free roaming in the EU, but fixed-fee roaming elsewhere, allowing you to take your home tariff with you for a set cost. Rather than paying this extra charge on all your devices, turn off data roaming on them and connect them all to a mobile hotspot. You'll pay this charge only once, but get all your devices online. Note that 5G roaming is not widespread, but it is currently offered by Vodafone and VOXI.
You can avoid using slow hotel Wi-Fi: When visiting hotels that still charge for Wi-Fi, you can get the kids online all day and at a lower cost than what the hotel would charge. Better still, you can avoid using the same network as all the other guests, which is usually slow and often has poor signal in your hotel room.
You can add 5G connectivity to a 4G device: Many of us have yet to jump on the 5G bandwagon, but where available it is seriously fast. A 5G mobile router will allow you to connect your 4G phone to the internet at 5G speeds.
You can get faster download speeds: Even if your device already supports 5G, you could potentially get faster download and upload speeds by switching to a MiFi that supports a faster connection. Just remember that 5G is not yet available everywhere, and purchasing a 5G hotspot will push up the price.
You can share storage across your own mobile network: If your MiFi supports a microSD card, you can share that storage across all your devices, which is especially handy if they don't support expandable storage themselves.
TP-Link M7350 - Best Overall Mobile Router
TP-Link's M7350 is a solid 4G mobile router that has the big benefit of being network-unlocked. That means although you'll pay in full upfront, you can choose any data deal from any UK network operator, and you aren't tied to a contract.
The TP-Link supports all three UK 4G LTE bands, with up to 150Mbps download speeds and 50Mbps uploads. It can create a wireless network for up to 10 devices, and supports a microSD card for shared storage and has an LCD that tells you the signal strength, how many devices are connected, how much data you have used of your total limit, plus the remaining battery capacity.
You can also use the LCD to cycle through a menu that caters to such options as toggling on or off data roaming, switching between 2.4- and 5GHz output, and choosing between 4G, 3G or a mixture of both.
A final option displays a QR code that takes you directly to Google Play or the App Store to download the tpMiFi app, which lets you manage users, alter the range, share files and read text messages.
The TP-Link's 2550mAh battery should be good for up to 10 hours of 4G connectivity, but lasts days on standby.
Skyroam Solis Lite - Best Travel Mobile Router
The Skyroam Solis Lite is a neat little Mi-Fi router that's interesting for two reasons (beyond that vibrant paint job): its cloud-SIM functionality and built-in power bank.
You can connect up to 10 devices at a time, and the Solis works in over 130 countries thanks to partnerships with more than 300 different carriers - so you can expect a solid 4G LTE connection just about anywhere you go. Because it uses a cloud-SIM, there's no need for a physical SIM card, and no need to sign up with a specific carrier.
The official accompanying app lets you check which devices are connected to your hotspot, keep an eye on your data usage, and buy more data as and when you need it. It's bright, clear, and easy to use, even for the non-technically minded.
Skroam promises 18+ hours of battery. Even better, the 4,700mAh battery doubles as a power bank, so if you don't mind sacrificing a bit of Wi-Fi battery life you can keep your phone or another device topped up when you need it.
There's also a lot of flexibility in how you pay, with Skyroam offering the ability to rent or buy devices, depending on for how long you wish to use it.
Huawei Mobile WiFi 3s (E5576-320) - Best Value Mobile Router
Available on contract through Three, the Huawei E5576-320 offers such great value that you'd be crazy not to simply buy the network-unlocked version outright.
This is a 4G mobile router that lets you connect up to 16 devices, with its 1500mAh battery offering a standby time of up to 350 hours and working time of up to 6 hours.
It's small, compact and easily portable - but, more importantly, it's functional, with up to 150Mbps download speeds and 50Mbps uploads.
There are no fancy extra features, with this affordable mobile router from Huawei instead concentrating on one primary task: getting your mobile devices online wherever you are.
TP-Link M7450 - Best 4G Mobile Router
The TP-Link M7450 is a newer, more advanced version of the M7350, but it's also more expensive and we think the older model currently offers better value.
Like the M7350, it's sold unlocked and should work with any major network, either in the UK or abroad. It supports Cat6 LTE, with 300Mbps downloads (double the M7350) and 50Mbps downloads; you can pick between either the 2.4GHz or 5GHz Wi-Fi bands; and you can connect up to 32 devices simultaneously - way, way more than most people will ever need.
Menu navigation is simple, and the clean UI makes the most of the two buttons and small screen to give you the info you need. For more complex setup - including USSD support, useful for connecting to many foreign networks - you can use either the web portal or free smartphone app.
The 3000mAh battery should give you an impressive 15 hours of working battery time. You even get a microSD slot, which supports cards up to 32GB and can be used as a quick way to share files between devices.
Skyroam Solis X - Best Smart Mobile Router
Very similar to the Lite model, and still just as orange, the Solis X has a few extra features in return for a slightly higher price.
This is a combined mobile router and power bank that uses a virtual SIM to deliver 4G LTE in 130 countries, which you can then share to up to 10 devices with the help of a redesigned (and very easy-to-use) app.
The battery capacity matches the Lite model at 4700mAh, with a USB-C port for charging. Its slim, light and rounded design is comfortable to carry in your palm or in a pocket.
The extra features are interesting. There's an 8Mp camera which you can use to take photos or record video through the accompanying app, but you would need to have your phone open to do so - and the chances are your phone has a better camera.
More interesting is smart assistant integration. You'll need to use IFTTT to set things up, and can then get the Solis X up to automatically record your location, post to social media when you change countries, or get weather reports based on your location. It has its own microphone and basic speaker, too.
Huawei 5G Mobile Wi-Fi Pro E6878-370 - Best 5G Mobile Router
Compact mobile routers that support 5G are still relatively uncommon. They are significantly more expensive than 4G routers, and 5G connectivity is not yet available everywhere.
However, if you are routinely within reach of a 5G signal, a 5G mobile router could offer a cheaper way to access faster mobile data speeds on all your 4G mobile devices than having to upgrade each one.
Huawei's 5G Mobile Wi-Fi Pro is available network-unlocked or on contact through O2. Buying it SIM-free will allow you to choose your own data package, stopping you being tied into a contract for longer than you'd like.
This is rather a chunky router with an 8000mAh battery inside, but it can also act as a power bank and offers 40W SuperCharge and both reverse wired (22.5W) and wireless (15W) charging.
Also housing a Balong 5000 chip, Huawei claims theoretical download speeds of up to 1.65Gbps.
MyWebspot - Best Rental Mobile Router
Many of the options in this chart are suitable for those who will regularly need the use of a mobile Wi-Fi router, but MyWebspot is more appropriate for those who have a one-off requirement.
If you're going on holiday abroad (potentially outside the realms of free roaming in Europe) and have several devices to get online, the service allows you to hire a hotspot for use by up to five devices in more than 100 countries.
Daily charges are calculated based on where you are going and for how long. At first glance they might seem steep, but they are nothing compared to what your mobile operator will charge you once you overstep your data allowance. It can also be very expensive to connect to Wi-Fi provided by some holiday resorts, which is often slow and time-limited.
The data is technically unlimited, but once you exceed the fair usage (1GB/day in Europe, US and Canada; 2GB in Mexico; fully unlimited in South East Asia; and 512MB everywhere else) the speed drops to an almost unusable 256kbps.
Setup couldn't be simpler. The device can be delivered directly to your resort (or home if you prefer), then you turn it on, wait a moment for it to connect to a local 4G LTE network, and pick it up on your mobile device as you would any other Wi-Fi network using the SSID and password printed on the label on the back. On your way home you pop it in the post box using the prepaid envelope.
MyWebspot claims download speeds up to 100Mbps, and uploads of up to 40Mbps. In our testing in Lake Garda, Italy, we recorded an average download speed of 33.5Mbps, and upload speed of 26.8Mbps. Naturally these speeds will decrease as you add multiple devices.
You'll get about eight hours battery life from the Mi-Fi router, which is supplied with the appropriate local charger for your holiday destination.
There's no companion app, which means even technophobes will get along with MyWebspot, though it would be handy to have some way of monitoring usage across multiple devices given that there's no LCD screen.
Huawei E5573 - Best Value Contract Mobile Router
Prices start from £9 per month with 2GB of data on a two-year plan, or you can get up to 40GB for £18 per month on a two-year plan.
A huge benefit of buying from Three is that if you're going abroad Three's Feel At Home policy lets you connect to the web with no roaming charges in several foreign destinations.
Can I use any SIM in a mobile hotspot?
Technically, yes. If you have a significant or unlimited data allowance with your mobile tariff you could simply take the SIM out your smartphone and insert it into a mobile router.
However, not all mobile operators support unlimited tethering (check your contract), various phone functions are not going to be available on your smartphone while it's missing its SIM, and you might regret the decision if you are overly generous with that shared mobile Wi-Fi connection and run out of data some time before the allowance renews.
You can now purchase data SIMs or SIM-only plans with big data allowances on PAYG or contract from all the UK's major mobile operators. Which option you choose is largely going to be based on how much data you need to use, and how frequently you need to use it.
If you want something only for when you go on holiday, choose a PAYG plan and pay for data only when you need it. If you want something to get around a flaky home broadband connection or for use on your daily commute, choose either a rolling one-month contract option or save a bit of money with a 12- or 24-month plan.
What are the best data SIM deals?
We'd advise looking for a deal from a well-known mobile operator that has reliable coverage in your area (or your holiday destination), with a big data allowance, no restrictions on tethering, free or cheap roaming, and a low monthly or PAYG cost.
You can check network coverage in your area for 2G, 3G, 4G and 5G on the mobile operator's website. Use the following links to jump straight to a mobile operator's coverage checker: Vodafone, EE, O2, Three, GiffGaff, Smarty, VOXI, iD Mobile, Virgin Mobile, TalkMobile.
There are many more companies offering data SIMs than we have listed here, but all are what are known as MVNOs, or mobile virtual network operators. This means they piggyback on another mobile network (Vodafone, EE, O2 or Three) for connectivity. As long as you have coverage with the big four, all the MVNOs should be covered in your area.
The best data SIM deals are always changing. We've collated more in-depth advice in our frequently updated guide to the best SIM-only deals, but our preference currently falls to Three. All its SIMs support 5G.
At Three you'll find a range of SIM options including unlimited data from £22 per month, or you can choose one of four PAYG packages that are valid for up to 12 months. For the latter, 24GB of data costs £60; 12GB of data costs £40; 3GB costs £16; and 1GB costs £10.
Smarty, which also runs on Three's network, currently has a great deal on 100GB of data for £15 on a one-month rolling plan. Tethering is unlimited in the UK.
How do I choose a mobile router?
There are three options when purchasing a mobile Wi-Fi router:
- Buy a device and data SIM bundle direct from a mobile operator in return for a fixed monthly subscription
- Buy a network-unlocked MiFi router and add your own data SIM
- Hire a mobile router to cover only the period you need (see MyWebspot or Skyroam Solis, both reviewed below)
Many people will automatically go to their mobile operator for a MiFi device, since it's an easy solution and you don't need to pay anything up front. But this isn't always the best idea.
If you buy a MiFi router from a mobile operator it will be locked to that network, preventing you from shopping around for the best data deal. You will also most likely pay over the odds if you choose to pay nothing up front but tie yourself into a two-year contract.
However, buy a network-unlocked router and shop around for a great-value data SIM plan and you will save money in the long run.
Note that the mobile hotspots offered by UK mobile operators are typically made by Huawei, but also Netgear, HTC and TP-Link. If you know the model you can usually find these devices available network-unlocked through retailers such as Amazon.
For example, Three's Huawei 4G Plus MiFi is in fact a Huawei Mobile WiFi 3s (E5576-320), while its Huawei HomeFi is actually a Huawei B311. O2's Huawei 5G Pocket Hotspot Pro is actually a Huawei 5G Mobile Wi-Fi Pro (E6878-370), and its Pocket Hostpot Pro Netgear M1 is a Netgear Nighthawk MR1100. Meanwhile, EE is stocking the HTC 5G Hub, while Three, Vodafone and O2 all list the otherwise currently unavailable Huawei E5573.