URL: https://diarybff.app/diary-with-password/ Date: 2026-10-28 Author: Daniel Chen, founder of Diary BFF Published by Diary BFF

Diary with password: the honest version

If you’re searching for a diary with password protection, you want one thing: a diary that stays shut unless you open it. Here’s the honest version of how Diary BFF does that, including the part that might surprise you.

It’s a PIN, not a long password

Diary BFF locks with its own 4-digit PIN. Not a long password with symbols, and not your phone’s passcode.

That’s on purpose. Diary BFF is made for writing at night, often in the dark, often with one hand. A long password at midnight is the kind of thing that makes you not bother. Four digits you can type without thinking means you actually keep the lock on.

What makes a short code hold

A short code is only weak if it can be guessed over and over. So:

Wrong tries count down. Enter the wrong PIN and you’ll see how many tries are left.
Then it makes you wait. After too many wrong tries, the diary asks you to wait before trying again, and the wait gets longer.
There’s no Face ID shortcut. Diary BFF doesn’t offer Face ID or Touch ID unlock, by design. The PIN is the key.
It’s separate from your phone. Someone with your phone passcode can’t open your diary. Someone who picks up your phone while it’s unlocked can’t open it either.

If you forget it

If you forget your PIN, you can start a reset with your phone’s own device authentication. For your privacy, the new PIN only unlocks after a 10-day wait, so someone who knows your phone passcode can’t use it to open your diary today. Your entries stay intact.

Pick a PIN you’ll remember, and don’t reuse your phone’s passcode. That would undo the whole point.

What’s behind the PIN

A night diary. You write whatever your head is doing, and it stays on the page. When you ask, your diary BFF 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. It remembers what you wrote, with the date.

Notifications never show what you wrote.
Your entries are not used to train AI.

Who it’s for

People who want their diary locked separately from their phone.
People who share a phone passcode with a partner or family.
Anyone who tried a lock that was too much effort and turned it off.

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.