Doing this without anyone finding out
Everything here is general information, not a diagnosis and not medical advice. If something about your sleep, your mood or your thoughts is worrying you, that is a moment for a professional, not a website.
This deserves to be said plainly, because it is one of the main reasons people never start. If you live with family, share a device, or have a partner who might scroll through your phone, then anything that names the problem on your screen is itself a risk.
That is not paranoia. It is a reasonable read of a real situation, and it is worth planning for rather than hoping about.
What to check
The app's name and icon. Anything on your home screen that announces what it is for defeats everything else. Safi is called Safi, and its icon is a wave — a glance tells nobody anything. If you use something else, check what it looks like in the app switcher, not just on the home screen.
Notifications. This is the most common way people are discovered: not by someone searching, but by a message appearing on a lock screen on a table. Turn them off, or use something that sends notifications with no text. In Safi they are off by default and, if you switch them on, carry no words at all.
Your browser history and address bar. An address bar that completes a domain after two letters is a reminder every time anyone opens the browser, including someone borrowing your laptop. Clear it, and clear saved suggestions specifically — they survive a normal history clear on some browsers.
Accounts. An app with an email login sends recovery mail to an inbox someone else may see. An app with a phone login sends a code that lights up a lock screen. This is the specific reason Safi has neither.
Downloads. If you export anything — notes, a journal — the file lands in a Downloads folder with a filename. Think about where you put it.
Have a way out of the page
Whatever you use, know how to leave it in one motion. Safi has a quick-exit button on every screen that navigates away and removes the page from the back button, so pressing Back does not bring it up again.
That is worth practising once while nothing is happening, so your hand knows where it is.
If someone does find out
It is worth having thought about this in advance rather than in the moment.
You do not owe a full account to anyone who finds an app on your phone. "It is something I have been working on for myself" is true, complete, and enough. What you say next is your choice, not something the discovery decides for you.
Questions about this
Will anyone find out I am using Safi?
The app asks for no email, no phone number and no password, so there is no account anyone can look up and no recovery message that could arrive in a shared inbox. It is called Safi and its icon is a wave — nothing on screen says what it is for.
Notifications are off unless you turn them on, and if you do they carry no text at all. Every page has a quick-exit button that leaves and removes the page from the back button.