It's all part of the iPhone's extremely handy Control Centre.
First, you need to learn how to access the Control Centre – and you may already know how.
If you're using an iPhone X or later (so no Home button), simply swipe down from the top-right corner of your screen.
To close it, swipe up from the bottom of the screen.
Be careful not to swipe too close to the centre or you'll open notifications instead.
On an older iPhone model (like the iPhone SE or iPhone 8) with a Home button, swipe up from the bottom edge of any screen.
And then to close the Control Centre, tap the top of the screen or press the Home button.
There are lots of features already built into the Control Centre, including toggles for brightness and and media playback.
But Control Centre can do so much more, if you customise it in the right way.
Go into Settings > Control Centre – it's just below General.
For instance, this is how you can access the iPhone's built-in Screen Recording feature.
You can have a Magnifier function, or a quick-access Music Recognition tool.
There's a button to toggle Low Power Mode on.
And you can even quickly enable Guided Access so you can show a person something on your iPhone without them being able to access other content.
You can quickly make Voice Memos, enable the Stopwatch, or turn Dark Mode on and off.
There are dozens of options to choose from, giving you much greater control over your iPhone.
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