A journal app with password protection, and what it means day to day

If you’re looking for a journal app with password protection, you’ve probably already noticed the catch: most journal apps “lock” with the same thing that unlocks your phone. Anyone you’ve handed your unlocked phone to is already past it.

Diary BFF has a password of its own. It’s a 4-digit PIN, separate from your phone’s passcode, and there’s no Face ID shortcut around it. This page isn’t about why that matters (we’ve written about that elsewhere). It’s about the practical side: what it’s like to set one, change one, and forget one.

Setting it

You set the PIN the first time you open the app. There’s no sign-up before that, and no profile to fill in. Four digits, typed twice, and you’re on tonight’s page.

Pick something you’ll remember at the end of a long day, with the lights low. Don’t reuse your phone’s passcode. The point is that the two are different.

Using it

The diary asks for the PIN when you open it. Your phone can be unlocked, the app can be in your recent apps, and it still asks. Notifications never show what you wrote, because they can appear on a lock screen, so there’s nothing to read around the lock either.

Changing it

You can change the PIN in Settings. You’ll be asked for your current PIN first. That step matters: someone holding your unlocked phone shouldn’t be able to set a new PIN and lock you out of your own journal.

Forgetting it

This is the part most journal apps with a password don’t explain, so here it is plainly.

If you forget your PIN, tap Forgot PIN on the lock screen and ask for a reset. Your entries are not lost; they stay locked. The diary stays locked for 10 days, and then you can set a new PIN.

If you remember the PIN during the wait, entering it cancels the request.

Why the wait? Because the person who taps Forgot PIN isn’t always the owner. Ten days is long enough that someone borrowing your phone can’t use it to get in, and short enough that you get your journal back.

What sits behind the password

A page that writes back, when you ask. Your diary BFF reads what you wrote and answers in a few sentences, with at most one question. The replies aren’t written by a person; your diary BFF is an AI that lives in your diary.
A memory with dates. Your diary BFF remembers what you wrote, with the date.
A letter on Sundays about your week.
Your entries are not used to train AI.

Who it’s for

People who share a phone, a couch, or a household, and want one thing that’s theirs.
People who’ve tried a “locked” journal and found that the lock was really just their phone.
Anyone who wants a password they can actually forget without losing everything they wrote.

Try it tonight

Download Diary BFF, set a PIN, and write one entry tonight. Your first reply comes with the app; more replies and the full Sunday letter are part of the full version.