A private journal app that keeps your writing yours
When you keep a journal, you write things you would not post anywhere. A private journal app has to earn that. Purple Diary does it two ways at once: the app locks behind a PIN and your device's biometrics, and the company behind it never sells your data or reads what you write. It is free, has no ads, and works on every device you own.
What "private" actually means in a journal app
The word private gets used loosely. Plenty of apps call themselves private because they add a passcode, then quietly run on ads, study what you type, or hand your data to other companies. That is not privacy. It is a locked door with the windows wide open.
A private journal app has to be private on two levels. The first is access: who can open the app and see your pages. The second, and the one people forget to ask about, is what the company does with your words once they exist. A diary holds the thoughts you are still figuring out and the moments you want to keep exactly as they were. If you suspect any of that is being read, scored, or sold, you start writing a tidier, safer version of your life, and the honesty that makes journaling worth doing disappears.
Locked at the door: PIN and biometrics
Access is the part you can see, so Purple Diary starts there. Set a PIN code when you begin, and on devices that support it, turn on biometric unlock with Face ID, Touch ID, or a fingerprint. From then on the app protects itself: it re-locks the moment you leave it, so a borrowed or already-unlocked phone still cannot reach your entries. You never have to remember to sign out. Close the app, hand the phone over, and your journal is sealed. The mechanics of the lock are covered in more detail on the diary app with a lock page.
No ads, and your data is never sold
The harder kind of privacy is the part you cannot see, so it comes down to trust and what the company actually does. Purple Diary shows no ads. There is no advertising business quietly shaping the app around what holds your attention, and no advertiser deciding what you should notice next. Just as important, your data is never sold. Your entries are not a product packaged up and passed to anyone else.
Purple Diary also does not read or reuse the content of your entries. The app runs so you can write, search, tag, and sync your own pages, and that is the only reason your words are touched at all. They are not mined for advertising, and they are not fuel for some other product. To set expectations honestly: this is about real data practices, not a cryptographic guarantee. Purple Diary does not claim end-to-end encryption or zero-knowledge storage. What it does promise is a clear, narrow use of your writing, which is exactly the question most "private" apps avoid.
You stay in control of your own writing
Privacy is really about control. Your journal belongs to you, and the app is built to keep it that way. You decide what to write, how to organize it with tags, what to attach, and which devices to keep in sync. Nothing about your entries is shared or surfaced for purposes you did not choose. The point of a private journal app is that the only audience is you, today and the version of you who reads it back later.
That control extends to the everyday experience. Purple Diary gives you a comfortable rich text editor, photo attachments and voice notes, mood tracking so you can look back over time, and a tagging system that makes any old entry easy to find. You can set the mood with ten light and dark theme colors, adjustable fonts and text sizes, and feed display options for how past entries appear. It is rated about 4.5 stars by more than 500 people, and runs on iPhone, iPad, Apple Watch, Mac, Android, Wear OS, Windows, and the web, syncing across all of them. Because the core journaling and the lock are free, privacy is not a feature you have to pay extra to keep. You can read what else is included on the free diary app page.
Who this matters for
Anyone can use a private journal, but the privacy matters most when the writing is honest. If you are working through anxiety, processing a hard season, or noting things you are not ready to say out loud, you need to know the page will not betray you. The same is true if you share a home or a device, travel often, or simply do not want your inner life turned into someone else's data. For all of them, a private journal app is not a nice extra. It is the whole point.
Frequently asked questions
What makes Purple Diary a private journal app?
Privacy is built into how the app works and how the company behaves. You can lock the app with a PIN and unlock it with Face ID, Touch ID, or a fingerprint on supported devices. Beyond the lock, Purple Diary shows no ads, does not sell your data, and does not read or reuse the content of your entries for anything other than running the app for you.
Does Purple Diary read or sell my entries?
No. Your entries are written for you, not for us. Purple Diary does not sell your data and does not use the content of what you write for advertising, training, or any purpose beyond letting you write, search, and sync your own journal.
How do I lock my private journal?
Set a PIN code when you start, and on devices that support it turn on biometric unlock with Face ID, Touch ID, or a fingerprint. The app re-locks when you leave it, so your journal is sealed again the moment you switch away or hand your phone to someone else.
Is the private journal app free?
Yes. Purple Diary is free to download and use with no ads. An optional subscription and a one-time lifetime purchase add extra features, but the app lock, biometric unlock, and core journaling are all free.