A diary with a password on iPhone: four private options

A lock screen keeps out strangers, not the people who already know your passcode or pick up your unlocked phone. If you want a diary nobody else reads, you need a second lock on the diary itself, and you need to know where the words are stored. Here are four ways to do it, with what each one protects.

What a password actually protects

Before choosing, ask three questions. Who am I keeping out: a partner, a parent, a roommate, or anyone who borrows the phone? Where are the words stored: only on this phone, or also in a cloud account someone else might sign into? And what happens if I forget the password: is the diary gone, or can I recover it?

1. Apple Notes with a locked note

Notes can lock individual notes with your iPhone passcode, Face ID, or a separate Notes password. It is free and already on your phone. The catch: the note list still shows locked notes by title, notes sync to iCloud, and anyone who knows your iPhone passcode can open a note locked with it. Use a separate Notes password if the person you are hiding from knows your passcode.

2. Apple's Journal app with Lock Journal

Apple's Journal app can require Face ID or your passcode to open (Settings, Apps, Journal, Lock Journal). It is free and built for daily entries and prompts. The same passcode caveat applies: the lock uses your device passcode, so it keeps out someone holding your unlocked phone, not someone who knows the code.

3. A diary app with its own lock

The App Store's diary-with-password apps add a PIN or Face ID lock inside the app. Before you pick one, read its App Privacy label on the store page (look for "Data Not Collected"), check whether it asks you to create an account, and check where entries are backed up. A lock matters less if every entry is uploaded to a server you cannot see.

4. Paper with a lock

A lockable paper diary has no cloud and no account. It also has a key or code anyone can find, and it can be read if it is left out. Paper is best for the long, reflective entry; it is awkward for the quick thing you want to get off your chest at 1 a.m.

A checklist before you write anything private

Who am I keeping out? Does the lock use my phone passcode, or its own? Does the app need an account or sign-in? Where are entries stored or backed up? What does the App Privacy label say? Can I delete an entry for good?

When the diary is really messages you will not send

Many private entries are things you want to say to one person: an ex, a parent, a boss. Writing them as a diary entry often does not help, because the urge is to text them. Unsaid is a diary written as text threads: you write to someone in a thread, press send, and the message stays on your phone, marked kept. It has no account, no cloud and no analytics, and its App Privacy label is Data Not Collected. Unsaid Plus, a one-time purchase, adds an app lock with Face ID or passcode. You can also burn a thread for good. If what you need is prompts, see the unsent letter prompts.