Someone asks to borrow your phone. To make a call, to look something up, to see a photo you just mentioned. You hand it over unlocked, and for the next few minutes everything on the device is available to them, not because they intend anything but because that is what an unlocked phone is.
Guided Access solves this in about five seconds, and almost nobody uses it because it is filed under Accessibility.
What it does
Guided Access locks the phone into whichever app is currently open. The Home gesture stops working, app switching stops working, and leaving requires a passcode or a triple-click plus Face ID.
You can also disable parts of the screen. Draw a circle around a button or an area and it stops responding to touch, which is how you hand someone a photo without giving them the rest of the library, or a browser without the address bar.
It was built for a different purpose, keeping a child or a person with certain needs inside one app, and it happens to be exactly the right tool for lending a phone.
Turning it on
Settings, Accessibility, Guided Access. Switch it on, then set a passcode under Passcode Settings, and choose whether Face ID can end a session.
Use a different passcode from your unlock code. If they are the same and the person watched you unlock the phone, the lock means nothing.
To start a session, open the app you want them to use and triple-click the side button. Draw around anything you want disabled, then tap Start. To end it, triple-click again and authenticate.
The options worth setting once
Inside a Guided Access session, tapping Options before you start gives you switches that most people never see, and two of them change what the feature is good for.
Touch. Turns off all touch input. The screen still displays, nothing responds. Useful for showing something you want looked at but not interacted with.
Time Limit. Ends the session automatically after a set period. Good for a child with a game, because the phone enforces the limit rather than you having to.
Keyboards. Turns off the keyboard entirely, which prevents typing anywhere in the app. If you have handed over a browser, this stops the address bar being useful even if you did not circle it.
Volume Buttons and Motion. Disables the hardware buttons and rotation. Minor, but they are the two things a child finds first.
Whatever you set is remembered for the next session, so this is a one-time configuration rather than something to think about each time. Set Touch off and a time limit for the child case, leave them on for the lending case, and switch between them when it matters.
Where it is genuinely useful
Handing over a photo. Open Photos to that one image, circle the area that scrolls to other photos, start Guided Access. They see the picture and nothing else.
Lending the phone for a call. Open the keypad or the contact, start a session. The call works and the rest of the phone does not.
A child with a game. The most common use, and the one it was designed for. No accidental purchases, no wandering into Messages.
Passing your phone across a counter. For a form, a booking reference, a QR code. Anything where the phone leaves your hand for a moment.
The five-second version, if you remember nothing else
Open the app, triple-click the side button, tap Start. That is the whole thing. You do not need to circle areas, you do not need to configure options, and you can set it up once and use it for years without opening the settings again. The reason it is worth the five seconds is that the alternative is not risky in some abstract way, it is simply that an unlocked phone is your whole phone, and there is no version of handing it over that is only the one app unless you make it so.
What it does not cover
Guided Access confines someone to an app. It does not lock individual apps.
If you want a particular app to require authentication every time it opens, that is a separate feature: iOS lets you lock or hide specific apps behind Face ID. Touch and hold the app icon and look for the option to require Face ID. That is the right tool for an app you want protected all the time, rather than during a lending session.
It also does nothing about notifications, which will still arrive during a Guided Access session. If previews are set to show, they show. That setting is under Settings, Notifications, Show Previews, and When Unlocked is the sensible default.
Screen Time as the longer-term version
For a phone regularly used by a child, Guided Access is the wrong shape because it needs starting each time.
Screen Time under Settings gives you app limits, content restrictions and a separate passcode that persists. Set it once and it applies whenever the phone is used, without you having to remember anything.
Guided Access is for a moment. Screen Time is for an arrangement.
Quick answers
Does the person know Guided Access is on?
Yes, immediately, because the Home gesture stops working. It is not a covert feature and it is not meant to be.
What if the triple-click does not work?
Check that Guided Access is enabled in Accessibility, and check Accessibility Shortcut in the same menu, since several features share the triple-click and it may be assigned elsewhere.
Can I use it on an iPad?
Yes, identically, and it is arguably more useful there because iPads are lent more often.
Does it stop someone taking a screenshot?
No. It confines the session to one app, it does not disable system gestures like screenshots.
Where to get it
The settings do the protecting; the lock screen is where you say something. DON'T Touch Phone Wallpapers has warning designs and contact-line layouts in HD, previewed in a phone-shaped frame before you save.
Set the Guided Access passcode now, while you are thinking about it. It is the part people leave for later and then never do.