Announcing Luma: simple cycle tracking for Android

We're building Luma, our third Android app. It's a clean, focused cycle tracker for anyone who wants to understand their menstrual cycle without the noise, the subscriptions, or the privacy compromises that come with most period apps.

The pattern behind Luma is the same one behind Vitals and Tiddle: we look at a category, find that what's available is either too complex, too invasive, or both, and build something focused and honest instead.

Period tracking apps are everywhere, but most of them have grown into something much bigger than a cycle tracker. They log symptoms, moods, sleep, and energy. They offer coaching, insights, and personalised content. They require accounts, sync to the cloud, and in several high-profile cases, have been found to share sensitive health data with third parties.

Menstrual data is among the most personal health data a person can have. We think it deserves to be treated accordingly.

What Luma does

Luma does one thing: helps you track your menstrual cycle clearly and simply. You log a period day by selecting a date and a flow level (spotting, light, medium, or heavy), with an optional note if you want to record anything else about that day.

From your history, Luma calculates your average cycle length and uses it to predict your next period and fertile window. These are shown on the home screen as a visual cycle wheel, along with your current cycle day, how many days until your next period, and which phase you're in (menstrual, follicular, ovulatory, or luteal). There's also a monthly calendar view that shows logged and predicted period days alongside your fertile window.

That's it. No symptom logging, no wellness scores, no coaching. Just a clear, honest view of your cycle.

Privacy, by design

Like all our apps, Luma stores data locally on your device using Android's standard app storage. It requires no internet connection and requests no network permissions. There are no accounts, no analytics, no advertising SDKs, and no cloud backup. Your cycle data never leaves your device unless you choose to share it.

We made this decision deliberately. The data Luma holds is sensitive. It can reveal things about your health, your body, and your life that you may not want shared. Building without cloud infrastructure is a stronger privacy guarantee than a privacy policy, because there is simply nothing to share.

Three apps, one approach

Vitals, Tiddle, and Luma are different tools built for different needs, but they share the same philosophy. Each is focused on a single job. Each is built without cloud infrastructure, accounts, or advertising. Each puts the user in full control of their own data.

We're not building a platform. We're building small, well-made tools that each do one thing well. Luma is the newest of them, but it was built with the same care and the same constraints as everything else we make.

Luma is currently in development. If you'd like to share thoughts on what you'd like to see, or be among the first to hear when it's ready, we'd love to hear from you.