Luna: Privacy and Period Tracking Done Right
*A story about privacy, frustration, and building something better for the people I care about.*
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Let me start with a confession: I never thought I'd build a period tracking app.
But here's what happened. A close friend showed me her period tracker one day—one of those popular apps with millions of downloads and glowing reviews. She was frustrated. Not because it didn't work, but because she'd just read an article about how these apps were selling user data to advertisers. *Her* data. The most intimate details of her body, packaged up and shipped off to the highest bidder.
"Why do they even need my data on their servers?" she asked.
And honestly? I didn't have a good answer. Because there isn't one.
The Problem No One Talks About
Here's a fun fact that isn't fun at all: most period tracking apps collect *way* more data than they need. We're talking about apps that know when you're ovulating, when you're intimate, your mood swings, your symptoms, your hopes of conceiving—and then turn around and share that information with "partners" for "better advertising experiences."
I'm sorry, but my friends and family deserve better than being a product.
So I did what any slightly obsessive developer would do: I built my own.
Enter Luna
Luna started as a weekend project. "How hard can it be?" I thought, naively. (Spoiler: it was harder than I expected, but also way more rewarding.)
The core principle was simple: **Your data stays on YOUR device.**
No servers. No accounts. No "anonymous" data collection that isn't really anonymous. No selling your cycle data to insurance companies or advertisers. Just you, your phone, and predictions that get smarter the more you use the app.
What Luna Actually Does
Let me walk you through what I built, because I'm genuinely proud of it.
Period Tracking That Actually Works
The basics had to be rock solid. Luna tracks your periods and predicts future cycles based on *your* actual data—not some generic 28-day assumption that works for approximately nobody. The more cycles you log, the smarter it gets.
BBT Tracking for the Data Nerds
Basal Body Temperature tracking is huge for understanding ovulation patterns. Luna lets you log your BBT daily and visualizes it in beautiful charts that would make any data scientist weep with joy. You can actually *see* your thermal shift.
Cervical Mucus & OPK Logging
For anyone trying to conceive (or trying *not* to), these details matter. Luna tracks it all without judgment and without sending that incredibly personal information to some server farm in who-knows-where.
Cycle Insights That Make Sense
This is where Luna really shines. Instead of drowning you in numbers, Luna shows you:
Symptom Tracking Across 12 Categories
Cramps? Mood swings? Skin changes? Energy levels? Luna tracks them all. But here's the cool part: over time, it helps you see patterns you might have missed. Maybe you always get fatigue during your luteal phase. Maybe your skin breaks out like clockwork on day 21. Luna helps connect the dots.
A Dashboard That Knows What Phase You're In
The home screen isn't static—it changes based on where you are in your cycle. During your period, you see different information than during your fertile window. It's like having a knowledgeable friend who always knows what's relevant *right now*.
Smart Notifications (That Stay On Your Device)
Period coming up? Luna can remind you. Fertile window approaching? Luna can let you know. But here's the difference: these notifications are scheduled and managed entirely on your device. No push notification servers tracking when you're ovulating.
Works Offline Because Privacy Means Privacy
Luna is a Progressive Web App that works completely offline. No internet connection required. Why? Because true privacy means your data never needs to leave your device—not even for a moment.
Your Data, Your Control
Want to export your data? Done. Want to delete everything? One tap. Want to create an encrypted backup that only you can access? Luna has you covered. You're never locked in, and you're always in control.
The Technical Stuff (For Fellow Nerds)
Luna is built as a PWA (Progressive Web App) using React and TypeScript. All your data lives in IndexedDB—that's local storage in your browser that websites can't access without your permission.
Backups are encrypted with a password only you know. I literally couldn't access your data even if I wanted to. (And I don't want to. It's *your* data.)
The app works on iOS, Android, and desktop. No app store involved, which means no arbitrary gatekeepers deciding what features I can or can't include.
Why Luna Is Different
I've looked at the major players in this space. Flo. Clue. Period Calendar. They're all fine apps with beautiful interfaces and millions of users. But they all have one thing in common: your data ends up on their servers.
Luna doesn't have servers. There's no backend collecting information. There's no "anonymous analytics" that might not be so anonymous. It's just an app that runs on your device and stays on your device.
Is this a harder way to build an app? Absolutely. I can't do fancy machine learning on aggregated data. I can't show you how your cycle compares to millions of other users. But honestly? I think that's a feature, not a bug.
Who Luna Is For
I built Luna for:
The Future
Luna isn't done. I keep adding features, squashing bugs, and making improvements. But the core promise will never change: your data stays yours.
If you've read this far, thank you. If you try Luna and like it, tell a friend. And if you have ideas for how to make it better, I'm all ears.
Because at the end of the day, we all deserve tools that work *for* us—not tools that turn us into the product.
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*Luna is free, open-source, and always will be. No subscriptions. No ads. No data collection. Just a period tracker that actually respects you.*
**Ready to try it?** Luna works on any device with a web browser. Just visit the app and start tracking—no account required.
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*Built with love, frustration at the status quo, and way too much coffee.*