QR code app blockers: how they work and how to set one up
Most app blockers put the off switch in the one place you shouldn't have it: on the phone, one tap away. A QR code app blocker moves it. The session that blocks your apps can only be ended by scanning a code printed on paper, and you decide where that paper lives. On your desk, it's a formality. In the hallway, it's a short walk. On another floor, it's a real decision.
This guide explains how it works on iPhone, how to set it up in about five minutes, and the few mistakes that quietly undo it.
How it works
Since iOS 16, Apple lets apps block other apps on your own iPhone through its Screen Time system (developers know it as Family Controls). You choose apps, categories and websites in Apple's own picker. When a session starts, iOS itself shows a shield screen instead of the blocked app. The blocker app doesn't hide or delete anything, and with Apple's system it never even learns the names of the apps you picked.
A QR code blocker adds one rule on top: the session only ends when you scan a specific code. The code is just a random piece of text, for example tenki-focus- followed by ten random characters. When you link it to a profile, the app remembers it. When you try to end the session, the camera opens and the app compares what it sees with what it stored. Any other code does nothing. No internet connection is involved, and the code is never sent anywhere.
Why a walk works better than willpower
Economists call this a commitment device: a choice you make now that makes a future choice harder to undo. A review by Bryan, Karlan and Nelson (2010) found that people who know they struggle with self-control often want such devices, and that firmer commitments tend to hold better for the people who choose them.
The walk to the code does two things. It adds delay, which gives the impulse time to fade. And it turns ending the session into a visible act: you have to stand up, leave the desk and go to the paper. Most of the time, somewhere between the chair and the hallway, you notice you don't actually want to stop. You walk back.
Set it up in five minutes
- Create a code. Use our free QR code generator. Each code is random and made in your browser; nothing is sent or stored. Any QR code works in principle, but a random one is better than, say, the code on a cereal box, which you could find again anywhere.
- Print it. Six to eight centimetres wide is plenty. Plain paper is fine; tape or a sleeve keeps it clean.
- Link it. In your blocker app, create a profile, choose the apps and websites to block, pick the QR code as the way to end, and scan the printed code once to link it.
- Place it wherever works for you (some ideas below).
- Start a session and test it once: try to end it without the code, then with it.
Where to keep the code
There is no single right place. It depends on your home, your day and how hard the evening is going to be. Some options, and what ending the session takes with each:
| Place | What ending takes | Notes |
|---|---|---|
| On your desk | A scan | No walk, but ending is still something you do on purpose, not a tap. |
| Hallway, kitchen, a bookshelf in another room | A few steps | Far enough that you stand up, close enough to reach easily. |
| Another floor, the basement, inside a cupboard | The stairs | Some people like that for evenings they know will be hard. |
| At work, in the car | A trip | The session ends when you get there. Good for a whole evening at home. |
| With a flatmate, partner or friend | Asking | Only if they're around when you need to end the session. Agree on that first. |
| Wallet, phone case, a photo on your laptop | Almost nothing | The code travels with you, so ending takes a second. |
What can go wrong
A photo of the code works as well as the paper
This is the most common way the setup quietly breaks. A QR code on a screen scans just as well as one on paper, so a photo on your laptop, or the PNG file in your downloads folder, is a second copy of the code. After printing, delete the file. If a copy already exists somewhere, create a new code, link it, and remove the old one from your profile.
You lose the paper, or you're not at home
If the only code is at home and you're at the library, you can't end that session early. That's the point, but plan for it. On days away, use a timer session that ends by itself, or a mode where a scan gives you a timed pause rather than ending everything. Keep a spare print somewhere hard to reach, like a sealed envelope in a drawer, not in your bag. Good blockers also keep a small number of emergency unblocks for real emergencies.
You delete the blocker app
Deleting the app that holds the block usually removes the block. Look for a strict mode that stops apps being deleted while a session runs, and turn it on only when you mean it.
The scan fails
Dim light and glossy paper are the usual reasons. Print in black on white, keep the code flat, and give the camera a second. A code with a small logo in the middle still scans, because QR codes carry built-in error correction.
QR code or NFC tag?
| Printed QR code | NFC tag | |
|---|---|---|
| Cost | Free | A few euros for a pack of stickers |
| Scanning | Camera, needs some light | Tap the top of the iPhone to it, works in the dark |
| Copying | A photo is enough | Not by accident; a photo does nothing |
| Placing | Paper, tape | Sticker, key fob or card, sticks almost anywhere |
If you want to try the idea tonight, print a QR code. If it works for you and you want something sturdier, an NFC sticker is the upgrade. We cover that in DIY Brick: an NFC tag as an app blocker.
How it works in Tenki
In Tenki, a QR code is one of three ways to end a session, next to ending it in the app and scanning an NFC tag. You link the code to a profile once. Then it works with the session modes you choose: Until you end it keeps the apps blocked until you scan; Pause by scan gives you a timed pause when you scan, and a second scan during the pause ends the session. Strict mode keeps you from deleting the app mid-session, and a limited emergency unblock is there for real emergencies. The QR generator is free, whether you use Tenki or not.
If the evening is the hard part rather than the tool, start with how to stop using your phone while studying. The code is one step in that setup, not the whole of it.