Journal app with password: what Face ID really protects, and what it doesn't

Your phone is on the table, screen up. Someone close to you picks it up to show a photo from the weekend and scrolls a little further than they meant to. That minute is why most people look for a journal app with a password, and a Face ID lock handles it well. The catch is that there are three ways into your entries, and Face ID shuts one of them. Below: what the lock actually does, where the real key to your entries sits, how to lock an app on iPhone with the tools that are already there, and what an app lock never touches.

Three ways into one journal

The first is an unlocked phone in someone else's hands. They borrowed it for photos, a kid is playing a game, a colleague is checking directions. This is what a lock on the app is for.

The second is a person who knows your passcode. A partner who watched you type it, or a relative you told "just in case". Face ID does almost nothing against them, and the next section shows why.

The third is not on the screen at all. It is the copy of your entries in the cloud, in a backup, or on a developer's server. An app lock does not reach it: it decides whether the app shows your entries, and leaves the stored data as it is.

Face ID checks your face. The key is your passcode

Apple's Platform Security guide is blunt about biometrics: Face ID and Touch ID make unlocking faster, and they do not replace the passcode.

Biometrics don't replace the device passcode. It is still required after startup and restart, and some actions, such as changing the passcode itself, always need it.

The passcode does more than open the screen. iPhone combines it with a key fused into that particular chip to derive the keys that encrypt data on the device. So guessing has to happen on the phone itself, and Apple makes every attempt deliberately slow, about 80 milliseconds. By Apple's estimate, trying every six-character passcode made of lowercase letters and numbers would take more than five and a half years. Wrong attempts also trigger growing delays, and with Erase Data turned on, ten failures in a row wipe the phone.

So entries in any journal on an iPhone are exactly as safe as the phone's passcode. If it is four digits half your household knows, a password inside the app won't fix that.

How to lock an app on iPhone

Since iOS 18 you can put a lock on any app, even one that has no lock of its own. Touch and hold the icon, then tap Require Face ID (or Touch ID, or Passcode). It also hides the app's content elsewhere. According to Apple, it stops showing up in notification previews, search, Siri suggestions and CarPlay.

Apple lists the limits too:

• The device passcode opens a locked app as well. Anyone who knows the code gets into the journal.
• The lock applies to that iPhone only and does not sync through iCloud.
• In a Family Sharing group, children under 13 can't lock or hide apps. Teens aged 13 to 17 can, but a parent can still see that the app was downloaded and how much time goes into it.

For a journal without its own lock, this is a good fix. If the app has one, the system lock sits on top without getting in the way.

Journal app with password vs Face ID: what a separate PIN buys you

Some apps offer a separate PIN or password that has nothing to do with the phone's passcode. This is what a password protected journal app adds on top of Face ID, and it is the only kind of lock that covers the second way in: someone who knows your iPhone code still can't read the entries.

It costs one thing, and it is a serious cost: you have to remember it. Type "diary app" into a search box and "forgot password" is one of the suggestions. Before the first entry, find out how the app lets you reset it. A reset by email means the app has an account, and some of your data or keys live with the developer. If there is no way to reset it at all, a forgotten password can cost you the whole journal.

Neither option is wrong. Pick by who you are keeping out. Face ID is enough for a passing glance. If the person you are worried about knows your phone's passcode, changing the passcode is simpler than carrying a second password in your head.

What the lock never touches: the copy in the cloud

If the journal syncs through iCloud, a copy of your entries sits in Apple's data centers, and the question becomes who holds the key to it.

By default iCloud uses standard data protection: your data is encrypted, and Apple keeps the keys for most categories so it can help you recover access. With Advanced Data Protection turned on, the keys for most of your data stay only on your trusted devices. For third-party apps, Apple adds a detail that is easy to skim past:

Third-party app data stored in iCloud is always encrypted in transit and on server. When you turn on Advanced Data Protection, third-party app data stored in iCloud Backup and CloudKit encrypted fields and assets are end-to-end encrypted.

Note the words "encrypted fields". End-to-end encryption covers only what the developer has marked as encrypted. Everything else stays under standard protection, Advanced Data Protection or not. So a line like "end-to-end encrypted with Advanced Data Protection" in an app's description doesn't tell you much yet. Ask what exactly is encrypted.

Here is Lanternly's answer. With Advanced Data Protection on, photos and voice recordings are end-to-end encrypted. The text of your entries is stored in iCloud under standard protection: encrypted, with the keys held by Apple. The app has no servers of its own, and the developer has no access to your iCloud.

A five-minute check

1. Phone passcode. Six digits or an alphanumeric code instead of four digits. If the journal is meant to stay closed to someone who knows the code, change it.
2. Journal lock. Turn it on in the app's settings, or by touching and holding the icon. Then send the app to the background and open it again: the lock should be there straight away.
3. Notifications and widgets. Look at your Lock Screen and Home Screen. A widget shows whatever was put into it, so check that it doesn't display the text of an entry.
4. The cloud. Decide whether you want Advanced Data Protection. Before turning it on, Apple asks you to set up a recovery contact or recovery key, because without them nobody can restore lost access, Apple included.
5. Everything else about the app. Where it stores entries, whether it needs an account, whether you can export it all: that is in the private journal app checklist.

If the journal belongs to a teenager, a few more questions come up, such as whether the family shares one Apple Account and who else picks up the phone. They're covered in our piece on a diary for teens.