This is the most dangerous Pointers tutorial we have ever done. It's not like it will risk your life and limb, it's more that it will risk ours if you do this and it goes wrong. For this is how to connect your MacBook or your Wi-Fi-only iPad to your iPhone in order to use the latter"s cell signal -- and your service provider may not like you for that. Worse, they may like you for it a lot, and be rubbing their hands as you pile on the devices and add to your bill and their hopes of a yacht this month at your expense.
So while the following works, and we are doing it right now in order to write to you, regard tethering as being for emergencies, okay? Whatever your plan, with whatever your provider, tethering should be seen as an exception, and an add-on to your regular service. Check whether you're allowed it at all, then check again, because some companies thought you meant your iPad, and will balk at a full-blown Mac using it.
Then, even if you can do it, watch for the amount of data you use. The sensible first thing is to never stream video over a tethering connection, but if you are using this to get a Mac online, there can be myriad other things going on that eat away at your limit.
What do you think, have you been warned enough? We wouldn't be doing this if it weren't stupendously useful at times, so it's worth taking a moment to do it right. The following was tested on the current iOS 8.4, and on a 10.10.2 OS X Yosemite, but will work with older systems.
Go somewhere that has no Wi-Fi signal. Purely for the purposes of this article, go to somewhere exotic with sunshine, gorgeous scenery, and no Wi-Fi. You can't bill us for that, but you can send a postcard.
On your iPhone, go to Settings. You're looking for an option called Personal Hotspot, but where it is varies and actually changes, too. Depending on your carrier and also on your location, you will either find it as a top-level Settings item or buried a little under a general one called Mobile. The presence of this option is determined by your carrier, so it may not be there if your plan or carrier doesn't allow tethering. This is now fairly rare, but not too long ago it was quite common for certain types of plans, and certain tight-fisted carriers.
Whichever it is, find it and switch it to On. Your iPhone is now ready to take its own cellular data, and broadcast it as a short-range Wi-Fi network to your other devices. To stop the massed hoards on your train from trying to clamber on to your signal and your dime, there is a password. This has been much improved in iOS 8: it used to be a common word, followed by a few digits. Now it's a proper mixed-case, letters and numbers job but as it stands, your iPhone sets it for you. You can change it if you like, but it's secure enough now that we haven't bothered. Changing it to something simpler may allow clever people to figure it out and leech off your cellular, so keep it strong.
Go to your iPad
It's quickest to show you the iPad one first rather than the Mac, but the principle is the same. Where you usually select a Wi-Fi network, you instead have to ... select a Wi-Fi network. Same thing. Exactly the same thing in the same way, except that the Wi-Fi you're tuning in to is coming from your iPhone.
On your iPad, open Settings, switch on Wi-Fi if it's not already on, and choose your phone's network. It will be very clearly marked with your name and iPhone in the title, plus instead of a Wi-Fi icon you get a new symbol like chain links. It's saying the same thing, that you're on a Wi-Fi network, but it is constantly reminding you that this is via your iPhone. You don't want to forget and live off the tethered connection until your next bill comes in.
You will be prompted for the password the first time you connect, but after that, the iPad will automatically connect. After you've done this once, the whole process can become more automated. Apple makes it sound as if whenever you picked up your Wi-Fi-only iPad and needed a signal, it could spot your nearby iPhone and use that. It's true. It can. We just find that sometimes it automatically works, sometimes it doesn't.
You can say that for this whole process. Sometimes your iPad won't connect to your iPhone, and you can't see a reason why. Nobody's driven over your iPhone in the last few minutes, have they? The solution is to try connecting again. Sometimes a third time, occasionally a fourth. We've not found out if it ever takes a fifth, because by that time we give up.
One thing we have spotted that makes a difference is when your iPhone's cell signal is poor. It may be that below a certain signal strength, it knows not to bother allowing a tethering connection, but we've not been able to prove that. We have almost invariably managed to connect after a few goes, and most of the time it is just once.
On your Mac
Macs expect a full Wi-Fi connection, so they will do a lot in the background that you're not expecting: much software will check for updates, and you may have set some to automatically download gigabytes of things. For that reason, some service providers will actually say no at this point: you thought you checked about tethering, but still you get a web page saying "Are you using a computer?" followed by some apology about how nope, not a chance, you're not using our cell service for that. This is annoying, but it is saving you a potentially very large bill for data.
If that is going to happen, it will pop up after you've done the same connecting to a Wi-Fi signal. You get the same connection symbol that your iPad has, and that will replace the Wi-Fi logo in your Mac's menubar. You will also see your tethering connection, followed by an option saying something like "Disconnect from iPhone." Everything is there to make you remember what you're doing, and give you the option to quickly switch off.
Just so you don't forget
You think we're going on about this? Tether anything to your iPhone, and your iPhone will not let you forget. The moment anything connects, you get a big blue stripe across the top of your screen saying so. It stays there. No matter what application you're using, everything gets squished down enough to allow the banner to stay there.
It will typically also say "Personal Hotspot: 1 Connection," and it will throb that text constantly. To stop tethering, you can tap on that blue banner, and it will take you straight to the Personal Hotspot setting where you can just switch it to Off.
Three last things. Tethering will never be adequately quick: you're sharing a cell connection, you're routing everything through your iPhone, it'll be delayed at every step. It will also be hot: your iPhone will get hotter, because it is under constant use. That leads to the third thing: tethering will also eat away at your battery power, because your phone is being stress-tested all the time.
All of which sounds like it's too tedious to do, and too much trouble to bother with, but if you can do it, do. Sitting in a train station logged in to your email is often a lifesaver.
-- William Gallagher (@WGallagher