iPhone hacks: 10 hidden Apple iOS features you need to know

The iPhone is now 10 years old. As it enters double figures, we might think we know it well – but there's a lot still hidden.

Apple started selling the phone exactly 10 years ago, beginning a revolution that would see smartphones redefine many of the most fundamental parts of our lives.

But for all that, the iOS software that powers iPhones is still something of a mystery. The handsets in our pockets include some of the most sophisticated software ever made – so it's no surprise that some of it is still undiscovered.

Here's a rundown of all the hidden tricks that you might not have stumbled across while using your phone.

Secret gestures

Apple makes most of the obvious ways to interact with your iPhone as clear as they can be. But it also hides a lot of extra gestures – ones that you might not even realise you need.

If you press the green call button in the Phone app, for instance, you'll be able to redial the last number you called. And if you're in something like the App Store, you can press 10 times on any of the menu buttons at the bottom to reset the cache, if something is playing up.

Within specific apps, there's even more options. Safari has a range of useful little secrets: open up the tab menu by pressing the button in the bottom right corner and then press and hold the "+" to be given the option to open up recently closed tabs. And – this one is incredibly useful, and relatively new – press and hold the "Done" button in the same view to get the option to close all of your Safari tabs at once.

Some gestures don't even need the screen. If you hold down the power button like you're going to turn the phone off, for instance, but when the slide to power off option appears hold down the menu button, your phone will reset itself and flush out the RAM, potentially getting rid of any apps hogging up space and slowing everything down.

This is even more true of the iPad, which uses its extra screen size to offer new ways of interacting with it. You can close an entire app just by swiping all your fingers in together, for instance, and can switch between them by putting all of your hand on the screen and moving it across.

Extra camera tricks

In its 10 years on the Earth, the iPhone has become the most popular camera in the world and brought with it a revolution in how we take and share pictures. Much of that has been driven by apps like Instagram – but the built-in camera app has hidden and useful features, too.

For instance, when you're recording a video, you can press the other little round button that appears in the corner of the screen to take a still picture as well.

And if you hold down the photo button while taking a picture, the camera will switch to burst mode and take a lot of pictures – perfect when you're trying to photograph a moment of action.

Improve your reach

Apple has been expanding the size of iPhones in the last 10 years, meaning the original one looks tiny compared with current models. But that original phone was also easy to hold in the palm of your hand – not something that can be said of the gargantuan Plus-sized models.

To allow you to cope with that, Apple added a feature called Reachability, though it doesn't talk about it much. It's activated by just tapping – not pressing down – on the home button twice.

When you do that, the entire top of the iPhone screen will be moved down, putting the parts of the screen that you can't normally get to within easy reach. That's perfect for small-handed people using the huge-bodied iPhone 6 Plus, or for anyone trying to use the bigger phones with one hand.

Hidden spirits

The compass app seems like a strange addition – unless you're particularly given to mountaineering or are leading a Scout troop, you've probably never had call to use it. But that might have kept you from finding the part of the app that's actually useful.

Open up the app and flick to the right and you'll be given access to a spirit level, which uses the phone's sensors to find out how flat it is. That can be perfect for a range of things – measuring whether pictures or floors are straight, for instance.

Access accessibility

Apple works hard on accessibility, something that it doesn't always show off about. That means there's a range of features built into iPhones to make them easier to use – some of which might go entirely unknown.

Head to the Accessibility pane in the Settings app, and you'll find the place to turn all of those on. They include features like the ability to turn on a magnifying glass, to see smaller bits of the phone's display, or to reduce the motion that can lead some people to feel traffic sick while navigating around the phone.

You can also turn on a setting so the iPhone's torch flashes when you get a notification, for instance, if you have trouble hearing it. It's worth having a look through all of this part of the Settings and seeing what you can find.

Take a shortcut

Autocorrect might be responsible for a lot of embarrassing situations where it picks the wrong word. But you can use it to save an awful lot of time.

By using the Text Replacement options in the Keyboard settings, you can add things you often type. The default example that Apple enables is "omw", which can autocorrect to "on my way", but you can add whatever words you want.

If you find yourself typing out an address a lot, for instance, then add that address to the substitutions and give it a shortcut like "addy". Then whenever you type that little word, the phone will give you the entire address and you can let the phone do the work.

Use the remote

The little remote built into your iPhone earphones is useful for the obvious: playing and pausing, and moving the volume up and down. But it does a lot more, too.

Perhaps the most significant of them is that you can use the volume up button as a way of triggering the camera, just like you can with the corresponding button on the side of the phone.

Check what's hogging your battery

The iPhone has a lot of features built to name and shame the apps that are using up your valuable resources. And perhaps the most valuable resource on the iPhone is battery – without which nothing else works.

Head to your phone's settings and search out the Battery option. Inside there, you'll get a list of the apps that have used the most battery over the last 24 hours and seven days. See if you can see anything that's running in the background when it shouldn't be – Facebook is a repeat offender in this respect, and you can save a lot of battery by deleting that from your phone – though it's likely you won't be surprised by the things that are at the top, since they're probably the ones you use the most.

It's also from this page that you can turn on power saving mode, which toggles a load of switches in the phone to make the battery last longer if you're worried about running out. It can be found quickly if you have an iPhone 6s or 7 – 3D touch on the Settings app and you'll see a shortcut to get straight there.

And check your storage

Probably the second most important resource on your phone is storage – again, once it's full, you can't do anything else with your phone. So if you head to the usage settings but click storage instead, the phone will bring up a big, sorted list of all the apps that are taking up space inside your handset.

There, you can look for the apps that seem to be hogging up a lot of storage, and particularly keep an eye out for ones that you haven't used for a while. Some common offenders like Facebook and Twitter might be taking up a lot more space than you expect – you can clear some of that out by deleting the apps and reinstalling them, which will have the effect of getting rid of some of the crud.

Turn everything yellow

Apple quietly introduced a new feature to everyone's iPhone this year, with a relatively low-profile software update. It's called Night Shift, and it's intended to make you sleep better, by turning the screen yellow.

Apple – and others – claim that taking away the blue from the screen and upping the yellow stops the phone's screen from being so harsh, and keeps the brain from being tricked into thinking that it's still daytime and so making it harder to sleep. The scientific evidence for that isn't so clear, but turning on the feature certainly does make everything a little less glaring.

You can activate it by opening settings and searching for Night Shift at the top of the screen. From that options page you can schedule it to come on at night and go off at sunrise – or any other time – as well as turning it on manually and deciding just how yellow it should be.