How to tell if a calculator app is fake on iPhone and Android

Maybe you’ve spotted a second calculator on your child’s phone, or seen a news segment about vault apps, and now every calculator looks suspicious. That’s not paranoia: plenty of apps on both stores look and work like a calculator but open a hidden vault when someone types the right code.

We make one of them, Calculator Locker, so we know which details give these apps away. Below are the checks we’d run ourselves, with exact steps on iPhone and Android, followed by the part that matters more: what finding one does and doesn’t tell you.

The checks at a glance

Two calculators, or a name that doesn’t match

Most phones come with a calculator: Apple’s on iPhone, Google’s or Samsung’s on Android. A second one proves nothing, since plenty of students install a scientific calculator, but it’s the first thing to look at.

On iPhone

1. Swipe left past your last Home Screen page to open App Library.
2. Tap the search field at the top. You get every app on the phone in alphabetical order, except hidden ones.
3. Look under C, and scan the rest for calculator icons with other names.

iOS doesn’t let an app rename itself, so the label under an iPhone icon is the app’s own name. Watch for an icon that looks like a calculator but carries a different name, and for names like “Calculator#” or “Secret Calculator”. A home-screen icon can also be a Shortcuts bookmark that opens some other app; the real app still sits in App Library.

On Android

1. Open the app drawer and search for “calc”.
2. Open Settings → Apps → See all apps (on Samsung, Settings → Apps). This list shows each app’s name as Android knows it.
3. Tap anything calculator-like. Many phones show an App details link near the bottom of App info, which opens the app’s Google Play page and its full store name.

On Android an app can change the name under its icon, and many vault apps only change it on the home screen. In a 2022 study of 20 Android vault apps, 17 didn’t keep their disguise in the phone’s app list. A “Calculator” icon that turns into “Vault” or “Hide Photos” in Settings has answered your question.

Check storage and screen time

This is the hardest thing to disguise. A calculator needs almost no space, and nobody lives in one.

Storage

• iPhone: Settings → General → iPhone Storage. The list is sorted by size; tap an app for details.
• Android: Settings → Apps → See all apps → tap the app → Storage & cache (just Storage on Samsung).

For scale, the 2022 researchers measured a real calculator at 6.10 MB on an Android phone, while the smallest calculator-disguised vault they tested took 35.17 MB before any files were added, and grew quickly once files went in. Sizes vary between apps and versions, so treat the number as a clue, not a rule. But a calculator holding hundreds of megabytes or a few gigabytes is storing something other than sums.

Screen time

• iPhone: Settings → Screen Time → See All App & Website Activity (App & Website Activity needs to be on). Apple says hidden apps still show up here.
• Android: Settings → Digital Wellbeing & parental controls (just Digital Wellbeing on some phones). Tap the chart to see screen time and times opened for each app.

Twenty minutes in a calculator the night before a maths test is homework. Forty minutes every evening, opened dozens of times a day, is worth a gentle question.

Check the App Store and Google Play

An app can be hidden on the phone, but the store keeps its own record.

On iPhone

• Everything downloaded: App Store → tap your photo → Apps & Purchase History. Your Apps includes apps that are no longer on the phone.
• Hidden purchases: App Store → your photo → your name → Hidden Purchases. Apple says hiding a purchase only removes it from the purchase list; it still appears in the full purchase history.
• Family Sharing: if your child is 13 to 17 and in your family group, Apple says you can see when an app was downloaded and how much it’s been used, even if they’ve hidden it.

On Android

In the Play Store, tap your profile icon → Manage apps & device → Manage. That’s everything installed from Play, listed under its store name. Tap This device and switch to Not installed to see apps that have been removed. As NNEDV’s Safety Net project points out, deleting an app doesn’t erase that history.

Search the store and look for “Open”

Search either store for “calculator vault”, “calculator lock” or “secret calculator”. Apps already on the phone show Open (or Installed) instead of Get or Install. It’s a quick way to check the popular ones without scrolling through every app.

Look for hidden apps and private spaces

iPhone (iOS 18 and later)

Any app can now be hidden. It disappears from the Home Screen, App Library and search, and moves into a Hidden folder at the bottom of App Library that opens with Face ID, Touch ID or the passcode. The same list is in Settings → Apps → Hidden Apps, behind the same check. According to Apple’s personal safety guide, hidden apps’ names still appear in Screen Time, in Battery and in App Store purchase history. Children under 13 can’t hide apps at all.

Android

Android 15 added Private space, a separately locked area whose apps vanish from the app drawer, notifications and Settings when it’s locked. It lives in Settings → Security & privacy → Private space. Two things to know. Searching “private space” in the app drawer can show a “Private space: Tap to set up or open” entry even on a phone that has never set one up, so that entry proves nothing; Google designed it that way. And Google says the space’s existence can’t always be hidden, for instance from someone who connects the phone to a computer.

Samsung phones have two more places to look. Any app can be taken off the Home and Apps screens (touch and hold the Home screen → Settings → Hide apps on Home and Apps screens), but Samsung says hidden apps still turn up when you type their name into the Apps screen search bar, so search for “calc” and “vault” there too. And Secure Folder, Samsung’s own locked area, can hide its icon. Our comparison of Android’s built-in hiding options covers what each one hides and from whom.

Check what the calculator is allowed to do

A calculator needs no permissions. Vault apps usually want some: the camera for break-in photos, access to photos to import pictures, sometimes more.

• iPhone: Settings → Privacy & Security → Camera, then Photos. Each lists the apps that asked. A calculator in either list deserves a second look.
• Android: Settings → Apps → the app → Permissions, or Settings → Security & privacy → Privacy → Permission manager to see every app with camera access. Also search Settings for “device admin”: some vault apps ask for device administrator rights, and an app with those can’t be uninstalled until they’re switched off.

What these checks show for our own app

Since we make one, here’s how ours fares against this list.

• The name. On iPhone (where the app is coming soon) it’s called “Calc” everywhere, because iOS doesn’t let apps rename themselves. On Android the home-screen name follows whichever of several calculator-style icons you pick, and the Settings app list calls it Calculator. Google Play’s list of installed apps still shows its store name, Calculator Locker: Photo Vault.
• The calculator. It really calculates: decimals, percentages, long chains of sums. Typing 2 + 2 tells you nothing.
• The way in. The vault opens when the owner types their code and presses =. There’s no button or menu to find.
• The extras. A decoy code opens a second, separate vault, and once camera access is allowed, three wrong codes trigger a break-in photo from the front camera.
• The giveaways. Its storage grows with what’s inside, like every vault, and it asks for the camera when break-in photos are switched on.

We don’t publish ways around it, for our app or anyone else’s. A bypass that works for a worried parent works just as well for a thief or a controlling partner.

What finding one means, and what it doesn’t

A vault app tells you someone wanted privacy. It doesn’t tell you what for. When researchers interviewed adults who use vault apps (SOUPS 2024), they were storing intimate photos, but also non-sexual photos of their own bodies, pictures from parties and scans of ID documents. Most wanted to stop someone glancing at their screen or scrolling too far through a borrowed phone, not to hide from a determined investigator.

Teenagers have the same mix, plus the particular embarrassments of being a teenager: photos they don’t want a sibling to see, a diary, screenshots of a group chat. Some of it may be something you’d want to know about, such as images they felt pressured to send or were sent by someone older. You can’t tell which from the icon, and how you find out often decides whether they’ll tell you.

How to talk to a teen about it

1. Start with the worry, not the app. “I found a vault on your phone” starts an argument about privacy. “I want to make sure nobody is pressuring you to send photos” starts a conversation about the thing you’re actually afraid of.
2. Be straight about how you found it. If you went looking, say so. Getting caught later costs more trust than owning it now.
3. Ask instead of demanding the code. With a decoy code, a code handed over under pressure may open a vault set up to look boring. Forcing it proves little and teaches them to hide better.
4. Agree what happens next. Phones out of bedrooms at night, which apps are fine, a regular check-in. Rules they helped write are easier to keep.
5. Use the official controls, openly. On iPhone, Screen Time with Family Sharing lets you set Content & Privacy Restrictions and Ask to Buy from your own phone, under Settings → Family → your child’s name. On Android, Google Family Link lets you approve downloads, block apps and see app activity. Both are built for this and visible to your child, which is the point.

What doesn’t work

Guessing the code

Many vault apps photograph whoever types wrong codes and show the owner the picture and the time, so the first thing your teen learns may be that you tried. And if a guess does work, it may be the decoy code, showing you a vault built to look dull and leaving you falsely reassured. Here’s more on break-in alerts and intruder photos, and on how decoy vaults work.

Monitoring apps that overreach

A lot of the parent advice about vault apps is published by companies that sell monitoring software. Some of those products go well beyond Screen Time or Family Link, reading messages or copying photos and sending them to the company’s servers. Then a third party holds the private pictures you were worried about, and if your teen finds the software, you’ve traded one secret for a bigger one. The same kind of hidden software, used on an adult’s phone, is what domestic violence advocates call stalkerware.

If you’re worried about a partner

Adults use these apps for the same ordinary reasons, and the checks above work on any phone. But going through a partner’s phone in secret rarely settles anything, and it can make things worse. If the real question is trust, it needs a conversation, or a counsellor, not a code.

If you feel controlled or unsafe, or think someone is checking or tracking your phone, talk to people who do this for a living rather than snooping back. NNEDV’s Safety Net project has practical guides to tech safety, and the National Domestic Violence Hotline is on 1-800-799-7233, or text START to 88788. Keep in mind that a hidden app can itself be found, as this whole page shows, and deleting it doesn’t erase its download history. A vault app is not a safety plan.