NFC app blocker: lock your phone with a $1 sticker

Updated 2026-09-24

An NFC app blocker ties your locked apps to a physical object. To end a lock early, you have to walk to that object and touch your phone to it. That short walk is the whole idea: the urge to check one more thing rarely survives a trip to the kitchen.

Why a physical key works

Most attempts to use the phone less fail in the same place: late, tired, one tap from the app. Reminders ask for permission at that exact moment, and the answer is usually yes. A physical key changes the question. Instead of “do you want to keep going?”, it’s “do you want to get up and walk to the fridge?” Much more often, the answer is no — and the evening goes differently.

The key doesn’t make leaving impossible, and it shouldn’t. It makes the impulsive exit slower than the impulse.

How NFC works on iPhone

NFC is the same short-range radio your iPhone uses for Apple Pay. It works over a few centimetres. An NFC tag is a small sticker with a chip and an antenna; it needs no battery and draws power from the phone when you hold them together.

A tag stores a few hundred bytes. For an app blocker that’s plenty: Hasp writes a single link that tells the app “this is your key”. Nothing personal is stored on the sticker.

To read a tag, hold the top edge of your iPhone close to it — that’s where the antenna sits.

Background reading

iPhone XS and later read NFC tags in the background, without opening an app. Touch the sticker and a notification appears; tap it and Hasp opens with your lock ended. Older models (iPhone 7 to iPhone X) can read tags too, from a Scan button inside the app.

Background reading needs the screen to be on. It pauses while Apple Pay or the camera is in use, in Airplane Mode, and right after a restart until you unlock the phone once.

Which NFC tags to buy

• NTAG213 — the most common and cheapest. 144 bytes, enough for a link. A good default.
• NTAG215 — more memory (504 bytes). Works just as well; you don’t need the extra space.
• NTAG216 — even more memory; also fine, usually a little pricier.

Things to check before you buy:

• The tags must be writable — not locked by the seller. Blank tags are.
• For metal surfaces like a fridge door, get anti-metal tags. Plain tags often won’t read on metal. The side panel of a fridge made of plastic, a wooden shelf or a door frame work with any tag.
• Stickers, key fobs and cards all work. Stickers are the easiest to hide in plain sight.

Setting up a sticker as your key

1. In Hasp, open your lock and choose how it opens: a sticker I write.
2. Hold the top of your iPhone to the blank sticker. Hasp writes its link and pairs the sticker with this lock.
3. Stick it where it belongs — see below — and test it once.

With Hasp Lifetime, each lock can have its own key: one for work hours on the desk in the office, another for evenings on the fridge.

Where to put it

The rule is simple: somewhere you have to get up and go.

• The fridge or a kitchen cupboard — the classic. Out of the bedroom, part of the house you visit anyway.
• The hallway or front door — good if evenings are the problem.
• Another floor — maximum friction for a late-night habit.
• The bottom of your gym bag — the phone unlocks at the gym, not before.

Not on the bedside table and not on your phone case. Then it’s just a button with extra steps.

No sticker? Two other keys

• A card you already carry with a contactless chip can serve as a key. Hasp remembers the card itself, not anything on it.
• A printed QR code works on any iPhone with a camera. Print it, stick it inside a cupboard, scan it to end a lock.

What if you lose the key

You’re not stuck. A lock still ends when its timer runs out, and the emergency exit is free and always there: ask for it in Hasp, wait 10 minutes, and the lock opens. Then set up a new key.

When a tag won’t read

• Hold the top edge, not the back. The NFC antenna sits near the top of the iPhone. Touch the top edge to the sticker and hold for a second.
• Take off thick or metal cases. A wallet case with cards or a metal plate can block the signal.
• Metal behind the tag. A plain sticker on a metal door often won’t read. Move it to wood or plastic, or use an anti-metal tag.
• Screen off. Background reading needs the screen on. Wake the phone first.
• Tag locked by the seller. If writing fails, the tag may be read-only. Use a blank, writable one.
• Older iPhone. On iPhone 7 to iPhone X, open Hasp and use the Scan button instead.

Is it secure?

The sticker holds a link, not a password. It only ends a Hasp lock on the phone it was paired with, and it can’t unlock the iPhone itself, open other apps or read anything from the phone. If someone copies it, the worst they can do is end your lock early — which you could do yourself with the emergency exit.

The honest limit

iOS lets the owner of a phone switch off Screen Time access in Settings, and every lock lifts when they do. An NFC key doesn’t change that, and no app can on an adult’s own device. What it changes is the easy path: instead of a tap in bed, ending early takes a walk.