Period trackers that don't share your data: how to choose a private one
The most private period trackers are built so the company never receives your cycle data: it stays on your phone, with no account. Apple's Cycle Tracking keeps Health data on device and encrypted in iCloud. Lulu has no account and no Lulu server holding cycle data. Mozilla's 2026 testing also praised Euki for keeping data on the device.
Why period app privacy matters
Cycle data is some of the most personal information you can put on a phone: when you bleed, when you have sex, whether you might be pregnant, how you feel. It's also valuable to advertisers. Several popular apps have been caught sharing more than users expected:
- Flo (2021): the US FTC finalized an order over allegations that Flo shared users' health data with marketing and analytics firms including Facebook and Google. In August 2025 a jury found Meta liable under California privacy law for collecting data from Flo users; Flo settled before the verdict.
- Maya (2019): Privacy International found Maya sent data to Facebook, including when the app was opened and details users logged. Its maker said it had stopped sharing personal data with Facebook.
- Stardust (2022 and 2026): TechCrunch found its 2022 encryption promise didn't hold up and that it shared phone numbers with an analytics firm. In July 2026 Mozilla research found it sending birthdate, birth control type, reproductive goals and symptoms to an analytics company, tied to an identifier. Stardust says the firm is contractually barred from selling or reusing it.
None of this means every app is dangerous. Many companies have improved. But it shows why the architecture of an app matters more than the promises on its home page.
Three privacy models
| Model | How it works | Examples | Trade-off |
|---|---|---|---|
| Company cloud with account | Your cycle data is stored on the company's servers | Flo, Clue, Stardust, Natural Cycles | Easy sync and backup; you rely on the company's policies and security |
| Platform-encrypted | Data on your phone, backed up to your own cloud with encryption the provider can't read | Apple Cycle Tracking (with two-factor authentication) | Strong privacy; fewer features |
| On-device, no account | Data stays on your phone; the app maker never receives it | Lulu, Euki | The company can't lose or share what it doesn't have; you rely on your phone backups |
How Lulu handles your data
- No account. No email, no password, no profile on our side.
- Cycle data stays on your iPhone. No Lulu server holds it. We never receive it, so we can't sell it, leak it or hand it over.
- Partner sync is optional and small. If you turn it on, only a small status (name, cycle day, phase and next period, plus today's mood, tomorrow's forecast and fertile window if you switch them on) is shared through Apple's iCloud with the one person you invite. Never symptoms, notes or history.
- No ads. Lulu is funded by Lulu Plus subscriptions (3-day free trial, then yearly).
The strongest privacy promise is not having the data at all. We'd rather say "we never receive your cycle data" than ask you to trust a policy.
How to check any period app in five minutes
- Read the App Store privacy label. Scroll to "App Privacy". Anything under "Data Used to Track You" may be linked to you across other companies' apps and websites.
- Check whether you need an account. No account usually means less data on someone else's server.
- Search the app's name with "FTC", "Mozilla" or "privacy". Independent reviews catch things marketing doesn't.
- Look for a data deletion option inside the app, and for an export so you can leave.
- Be wary of absolute promises. Stardust's 2022 encryption claim is a reminder that "fully private" needs proof.
What labels say today
From each app's US App Store page, October 2026, under "Data Used to Track You": Flo lists Purchases, Location, Identifiers and Usage Data; Clue lists Identifiers; Stardust lists Purchases, Identifiers and Usage Data; Natural Cycles lists Contact Info; Maya lists Usage Data. Labels are self-reported by developers and can change, so check the live page. For more on the risks, read do period apps share data? and is my period tracker private?
Frequently asked questions
What is the safest period tracker?
The safest are those where the company never receives your cycle data: no account, data on your phone. Apple's Cycle Tracking, Lulu and Euki work that way in different ways.
Can period tracker data be used against you?
Data stored on a company's servers can be requested by authorities with legal process. Data that never leaves your phone can't be requested from the company.
Does Apple share period tracking data?
Apple says Health data synced to iCloud is encrypted in a way Apple can't read when two-factor authentication is on.
Is Clue private?
Clue is a Berlin company under GDPR and says it never sells health data, but it is account-based and its App Store label lists Identifiers used for tracking.
Sources
- FTC: FTC Finalizes Order with Flo Health (June 2021)
- TechCrunch: Jury rules Meta violated California privacy laws by collecting menstrual health data from Flo (Aug 2025)
- Privacy International: How menstruation apps are sharing your data (2019)
- TechCrunch: Stardust shares users' health data with analytics firm, says Mozilla research (July 2026)
- Apple Support: Track your period with Cycle Tracking
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
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