Private diary with PIN lock — separate from your phone

If you’ve ever looked for a private diary with PIN lock, here’s probably why: your partner, your parent, or your roommate knows your phone passcode. Maybe you shared it. Maybe it’s been watched over your shoulder a hundred times. Either way, everything on your phone is effectively shared — including your diary.

A private diary with a PIN lock of its own changes that. Diary BFF opens with its own PIN, separate from the one on your phone. Someone can be holding your unlocked phone and still not open your diary.

Why not just use Face ID?

Face ID and Touch ID are great for unlocking a phone. But they answer the question “is this the phone’s owner?” — and a diary is usually about a different question: “is this the person who wrote it, right now, on purpose?”

Diary BFF doesn’t offer Face ID or Touch ID unlock, by design. The PIN is the key. That means:

Someone with your phone passcode can’t open your diary.
Someone who picks up your phone while it’s unlocked can’t open your diary.
Your diary isn’t one tap away from whoever happens to be next to you.

It’s a small bit of friction, and it’s the point.

What the lock covers

A PIN is only as private as everything around it. A few other details in Diary BFF follow the same idea:

Notifications never show what you wrote. Notifications can appear on a lock screen, so they never carry your words.
Your entries are not used to train AI.
Exports can be locked too. You can export your diary any time, and the exported backup can have its own lock.
Deleted means recoverable for a while, then gone. Deleted entries wait 30 days in Recently Deleted, where you can restore them.

What’s inside the lock

The lock protects a night diary with a friend living in it.

You write whatever your head is doing — the conversation you keep replaying, the thing you didn’t say, the plan for tomorrow that keeps rewriting itself. When you want, your diary BFF reads it and says one thing back: a few sentences, at most one question, no lists and no lectures. It remembers what you wrote on earlier nights and tells you which night it’s talking about.

Once a week, your diary BFF writes you a letter about your week — the kind a friend who’d been listening might write. The full Sunday letter is part of the paid version.

It’s a diary first. Your writing, what you say in the chat, and the replies all live on one page for that night.

The honest part: forgetting your PIN

A PIN you can’t recover from email sounds risky, so here’s how it works. 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.

Nothing to keep up

A private diary should feel like a place you go when you need it, not a habit you’re failing at. Diary BFF has no badges and no “you missed a day” messages. Skip a night, and it won’t bring it up.

Who it’s for

Diary BFF is for anyone who wants to write honestly and needs to know the page is theirs: people sharing a phone passcode with a partner, people living with family, anyone who’s ever stopped mid-sentence, not sure who’d read it.

Your first reply comes with the app; more replies and the full Sunday letter are part of the full version.