Private period tracker apps compared
The most private period trackers keep your data only on your phone and collect nothing: Euki and drip are free, open source and need no account. Apple Health keeps cycle data on your device, with end-to-end encrypted iCloud sync. Cloud apps such as Clue, Flo, Lunation, Natural Cycles and Stardust back up your data and measure their own ads; their policies differ in the details below.
What makes a period tracker private?
No app is private in every way. These are the questions that separate them, and the ones the tables below answer:
- Where is the data stored? Only on your phone, or on the company’s servers so it can sync and be restored.
- Do you need an account? An email address or a Google or Apple sign-in ties your logs to your identity.
- Is it sold, or shared with advertisers? What the privacy policy says about selling data and about health data in advertising.
- Does the app measure or target ads? Many apps share identifiers with ad and measurement companies to see which ads work, even when no ads appear in the app.
- What does the App Store label say? The “Data Used to Track You” section lists what may be used to track you across other companies’ apps and websites.
- Can you delete everything? In the app, by email, and how long it takes.
Privacy at a glance
| App | Account required | Where your data is stored | Sold or shared for ads | Ads and ad measurement | App Store: data used to track you | Deleting your data |
|---|---|---|---|---|---|---|
| Apple Health Cycle Tracking | No separate sign-up; it is part of the Health app. | On your iPhone. Optional iCloud sync, where Health data is end-to-end encrypted. | You choose which third-party apps and people can read your Health data. | Not applicable: built into iOS, with no App Store listing. | No App Store label (built into iOS) | Review, edit and delete Health data in the Health app at any time. |
| Clue | Yes. Clue has asked new users to create an account since 2019. | On Clue’s servers in the European Union (Amazon Web Services data centres in the EU). | Clue says tracked health data is never shared with or sold to advertisers. With your consent, de-identified data can be shared with research partners; you can switch this off. | To measure its ads, Clue processes install and subscription events with your device ID and IP address, using Apple Search Ads, Google Ads and Adjust. | Identifiers | Delete your account in the app, or email Clue to have all data, including data sent to third-party services, deleted within one month. |
| drip | No. | Only on your device. Your phone’s own cloud backup may still include it. | drip says it does not collect, retain or share any usage data or personal information. | None: no ads and no tracking. | None (Data Not Collected) | Settings › Data › Delete app data, or uninstall the app. |
| Euki | No. No account, email or phone number. | Only on your device; no backup or sync to other devices. | Euki says it does not collect, retain or share personal information. | None in the app. Some educational pages open in an in-app browser that loads those websites’ own trackers. | None (Data Not Collected) | Delete data on the spot or schedule automatic deletion; PIN lock available. |
| Flo | Anonymous Mode lets you use Flo without linking your name, email address or technical identifiers to your data; some features are not available in it. | On Flo’s servers, in your Flo profile. | Flo says it never sells personal data, does not share health data with third parties for marketing, and does not use Apple Health data for advertising. | With your consent, Flo shares technical identifiers (and your advertising ID if you allow tracking) with AppsFlyer, Firebase and TikTok Ad Manager to measure and improve its ads; it says health data is not included. | Purchases, Location, Identifiers, Usage Data | Request deletion in the app’s settings or by email; Flo says full erasure from its backups can take up to 90 days. |
| Lunation | No. Guest mode works without an account; Apple or Google sign-in can be added later from Settings. | In your account on Google Firebase, so it can sync and be restored. In guest mode it is stored the same way under an anonymous ID. | Never sold, never shared with advertisers and never used for ads. | No ads in the app. It measures which of its own ads brought you in (install, trial and purchase events, no health data) and shows Apple’s tracking prompt; the advertising identifier is used only if you allow it. | Purchases, Identifiers, Usage Data | Delete your account and all of its data in the app (Settings › Account › Delete Account). |
| Natural Cycles | Yes; an account with a subscription. | On Natural Cycles’ servers; it says data may be processed outside the EU/EEA with safeguards. | Natural Cycles says it never sells personal data, and that sensitive (health) data is not used for its ad audiences. | It matches hashed contact details, IP and device data with social media platforms to build custom and lookalike ad audiences. | Contact Info | Request deletion at any time; an account you stop using without deleting is kept for three more years. |
| Stardust | Yes. Privacy International’s May 2025 test required signing up with a Google account. | On Stardust’s servers. It says health data is tied to a random account ID and contact details are stored separately with an authentication provider. | Stardust says it does not sell data and does not use or disclose health data to serve digital advertising. | With your consent in device settings, Stardust shares internet-activity data with AppsFlyer and its partners and with Firebase to promote the app and measure its ads. | Purchases, Identifiers, Usage Data | Delete your health data in the app (profile settings) or request deletion by email. |
Apps listed alphabetically. App Store labels are from the US App Store, written by each developer and not verified by Apple. Scroll sideways to see every column.
Price, platforms and features
| App | Price model | Platforms | Standout features | Best for |
|---|---|---|---|---|
| Apple Health Cycle Tracking | Free; built into the Health app on iPhone. | iPhone and Apple Watch. | Period and fertile window predictions, pregnancy logging, and retrospective ovulation estimates from wrist temperature on Apple Watch Series 8 or later and Apple Watch Ultra. | iPhone and Apple Watch users who want a basic tracker that stays on their own devices. |
| Clue | Free to download. Optional Clue Plus; the US App Store lists $9.99 a month or $39.99 a year. | iPhone and Android. | EU data storage under the GDPR; opt-in research partnerships; Clue Conceive, declared on its US App Store listing as a regulated medical-device feature that predicts fertile days to aid conception; period, trying-to-conceive, pregnancy and perimenopause modes; wearable connections. Mozilla Foundation scored its privacy 8/10 in July 2026. | People who want their data stored in the EU, want to contribute to research, or use Android. |
| drip | Free and non-commercial, with no in-app purchases. | iPhone and Android. | Open source; fertility awareness with the symptothermal method and transparent calculations; data import and export; designed with gender inclusivity in mind. | People who want an open-source, device-only tracker and like to see how their fertility signs are interpreted. |
| Euki | Free, with no in-app purchases. | iPhone and Android. | Open source; information on contraception, abortion and sexual health; a care navigator (beta). Mozilla Foundation scored its privacy 10/10 in July 2026. | People who put privacy first and accept that nothing is backed up. |
| Flo | Free to download. Optional Flo Premium subscription; the US App Store lists in-app purchases from $1.99 to $59.99. | iPhone, Apple Watch and Android. | A large feature set: more than 70 symptoms and moods, articles and expert-led videos, an AI health assistant, partner sharing, pregnancy and perimenopause tools, and an Apple Watch app. Mozilla Foundation scored its privacy 7/10 in July 2026. | People who want a wide range of content and features, or who use Android or switch between platforms. |
| Lunation | Free. Optional Lunation Plus subscription, monthly or yearly; the yearly plan has a free trial for eligible new subscribers. See the App Store for current prices. | iPhone only (iOS). | Predicts your next period and fertile window from the periods you log; trying-to-conceive and pregnancy modes; Lock Screen and Home Screen widgets; optional Apple Health sync; a daily AI-written briefing, labelled as AI-generated (Plus). | iPhone users who want predictions, widgets and cloud backup without having to create an account. |
| Natural Cycles | Subscription needed to unlock core features; the US App Store lists $21.99 a month or $149.00 a year. | iPhone, iPad, Apple Watch and Android. | Authorised by the US FDA as a contraceptive app (De Novo, 10 August 2018). Uses temperature from a thermometer or a compatible wearable. For adults 18 and over. | Adults who want a regulated, hormone-free birth control method and are willing to measure their temperature. |
| Stardust | Free to download. Optional subscription; the US App Store lists $6.99 a month and yearly plans from $24.99 to $39.99. | iPhone and Android. | Moon-phase and astrology content, cycle sharing with partners and friends, a pregnancy mode, and wearable temperature data (Apple Watch, Oura). Mozilla Foundation scored its privacy 2/10 in July 2026. | People who enjoy moon-phase and astrology content and want to share their cycle with friends. |
Prices are US App Store prices on 10 November 2026 and change often; check the store in your country.
The apps, one by one
Apple Health Cycle Tracking
Built into the Health app, Cycle Tracking predicts your period and fertile window, lets you log a pregnancy, and with an Apple Watch Series 8 or later or any Apple Watch Ultra, estimates after the fact when you likely ovulated from wrist temperature. Health data stays on your iPhone unless you turn on iCloud sync, where Apple says it is end-to-end encrypted. It is iPhone and Apple Watch only, and Apple says it should not be used as birth control.
Clue
Made in Berlin, Clue stores data on EU servers under the GDPR and asks new users to create an account. It says health data is never shared with or sold to advertisers, offers opt-in research sharing with de-identified data, and declares its Clue Conceive mode a regulated medical-device feature to aid conception. It measures its own ads with Apple Search Ads, Google Ads and Adjust. Mozilla Foundation scored it 8 out of 10 in July 2026.Lunation vs Clue.
drip
An open-source, non-commercial app from Heart of Code, a Berlin non-profit. Everything stays on your device and its App Store label says “Data Not Collected”. It supports fertility awareness with the symptothermal method and shows how it reaches its results. It runs on iPhone and Android.
Euki
A free, open-source app from a non-profit. It needs no account, keeps data only on your device, can lock behind a PIN and delete data on a schedule, and includes information on contraception, abortion and sexual health. Mozilla Foundation scored it 10 out of 10 in July 2026. Euki has no backup or sync of its own.
Flo
One of the most widely used trackers, with apps for iPhone, Apple Watch and Android, and a large set of articles, videos and tools. Flo says it never sells personal data and does not share health data for marketing; with consent it shares technical identifiers with AppsFlyer, Firebase and TikTok Ad Manager to measure its ads, and Anonymous Mode unlinks your identity from your data. Flo settled FTC allegations about sharing health data in 2021. Mozilla Foundation scored it 7 out of 10 in July 2026. Lunation vs Flo.
Lunation
Lunation is iPhone only. It predicts your next period and fertile window from the periods you log, has trying-to-conceive and pregnancy modes and Lock Screen and Home Screen widgets, and works without an account. Your logs are stored in your account on Google Firebase so they can sync; they are never sold, never shared with advertisers and never used for ads. The app shows no ads but measures which of its own ads brought you in (install, trial and purchase events, no health data) and shows Apple’s tracking prompt, which is why its App Store label lists data used to track you. It is made by Holdone Software SRL, a small independent company in Romania.
Natural Cycles
The only app here authorised by the US FDA as a contraceptive (De Novo, August 2018). It uses your temperature from a thermometer or a compatible wearable, needs a paid subscription for its core features, and is for adults 18 and over. Natural Cycles says it never sells personal data; it uses hashed contact, IP and device data to build ad audiences on social media platforms, without sensitive data.
Stardust
Stardust pairs cycle tracking with moon-phase and astrology content and lets you share your cycle with friends. It says it does not sell data and does not use health data for advertising, and that health data sits under a random account ID separate from your contact details. With consent it shares activity data with AppsFlyer and Firebase for its marketing. Mozilla Foundation scored it 2 out of 10 in July 2026, after seeing logged symptoms sent to an analytics data pipeline.
Where Lunation fits, honestly
If you want nothing to leave your phone, Euki and drip collect less than Lunation does: Lunation keeps your logs in the cloud, measures its own ads, and its App Store label lists data used to track you (Used to track you: Purchases, Identifiers, Usage Data. Linked to you: Health & Fitness, Purchases, Contact Info, User Content, Identifiers, Usage Data, Sensitive Info. Not linked to you: Purchases, Diagnostics.). What Lunation offers instead is cloud backup without an account, predictions from your own periods, trying-to-conceive and pregnancy modes, widgets, and a promise that your health data is never sold, shared with advertisers or used for ads. It is not available on Android, and it is not a contraceptive.
How we checked
On 10 November 2026 we read each app’s current privacy policy and US App Store listing (price, platforms and App Privacy label), its Google Play listing, regulator and court records, and the Mozilla Foundation’s July 2026 privacy reviews where one exists. Every statement links to a source below; anything we could not confirm was left out. We did not run our own network tests.
Frequently asked questions
What is the most private period tracker app?
The apps that collect the least are the ones that keep everything on your phone: Euki and drip need no account and their App Store labels say “Data Not Collected”, and Mozilla Foundation scored Euki 10 out of 10 in July 2026. Apple Health also keeps cycle data on your device, with end-to-end encrypted iCloud sync. The trade-off is that device-only apps have no backup or sync of their own.
Do period tracker apps sell your data?
Each cloud app compared here, Clue, Flo, Lunation, Natural Cycles and Stardust, says it does not sell your data. All five also share identifiers, usage or contact data with advertising and measurement partners for their own advertising, so check each app’s privacy policy and the “Data Used to Track You” part of its App Store label.
What does “Data Used to Track You” mean on the App Store?
It is the part of an app’s App Privacy label listing data that may be used to track you across apps and websites owned by other companies, usually for advertising or ad measurement. Developers write these labels themselves, and the App Store notes that Apple has not verified them.
Which period trackers work without an account?
Euki, drip and Apple Health need no separate account. Lunation has a guest mode with no sign-in, although your logs are still stored in the cloud under an anonymous ID, and Flo’s Anonymous Mode unlinks your name, email address and identifiers from your data. Clue, Natural Cycles and Stardust use accounts.
Is any period tracker approved as birth control?
Natural Cycles was authorised by the US FDA as a contraceptive app in August 2018 and uses your temperature. Clue, Flo, Stardust, Apple Health Cycle Tracking and Lunation say they should not be used as birth control.
What do I give up with an app that stores data only on my phone?
Mainly backup and sync. If you lose or replace your phone, a device-only app such as Euki may not have a copy of your history, although drip notes that your phone’s own cloud backup can include its data. Cloud apps restore your history on a new phone, but your data then lives on the company’s servers.
Sources
- Log menstrual cycle information in Health on iPhone. Apple Support.
- View menstrual cycle predictions and history in Health on iPhone. Apple Support.
- Log a pregnancy in Health on iPhone. Apple Support.
- Receive retrospective ovulation estimates on Apple Watch. Apple Support.
- Health App & Privacy. Apple.
- iCloud data security overview. Apple Support.
- Clue Period & Cycle Tracker on the App Store (US): price, App Privacy label and medical device statement. Apple App Store.
- Clue: Period & Cycle Tracker on Google Play. Google Play.
- Clue Privacy Policy (last updated 29 September 2026). BioWink GmbH.
- Why do I need an account to use the newest version of Clue?. Clue.
- Privacy Review: Clue (16 July 2026). Mozilla Foundation.
- drip period & cycle tracker on the App Store (US): App Privacy label and description. Apple App Store.
- drip period & cycle tracker on Google Play. Google Play.
- drip: secure and open-source menstrual cycle tracking. Heart of Code e.V..
- drip Privacy Policy. Heart of Code e.V..
- Euki on the App Store (US): App Privacy label and description. Apple App Store.
- Euki on Google Play. Google Play.
- Euki Privacy Policy & Terms of Service (effective June 2024). Euki, Inc..
- Privacy Review: Euki (16 July 2026). Mozilla Foundation.
- Flo Cycle & Period Tracker on the App Store (US): price, compatibility and App Privacy label. Apple App Store.
- Flo Ovulation & Period Tracker on Google Play. Google Play.
- Flo Privacy Policy (effective 31 August 2026). Flo Health.
- Privacy Review: Flo (16 July 2026). Mozilla Foundation.
- Lunation on the App Store (US): price, compatibility and App Privacy label. Apple App Store.
- Lunation Privacy Policy. Holdone Software SRL.
- Natural Cycles: Fertility App on the App Store (US): price, compatibility and App Privacy label. Apple App Store.
- Natural Cycles - Birth Control on Google Play. Google Play.
- Natural Cycles Privacy Policy (last updated 7 August 2025). NaturalCycles Nordic AB.
- De Novo classification DEN170052: Natural Cycles, contraceptive software application (granted 10 August 2018). US Food and Drug Administration.
- Stardust Period Tracker on the App Store (US): price and App Privacy label. Apple App Store.
- Stardust Period Tracker on Google Play. Google Play.
- Stardust Privacy Policy (last updated 28 October 2026). Stardust.
- Your data is private. Period.. Stardust.
- Stardust: research findings (6 May 2025). Privacy International.
- Privacy Review: Stardust Period Tracker (16 July 2026). Mozilla Foundation.
- Developer of popular women’s fertility-tracking app settles FTC allegations that it misled consumers about the disclosure of their health data (13 January 2021). US Federal Trade Commission.
- Jury ‘sends a message’ on app privacy in ruling against Meta (August 2025). The Record by Recorded Future News.
Last checked: . Prices and App Store privacy labels are from the US App Store on that date. Written by the Lunation editorial team.
Medical disclaimer. Lunation is made by Holdone Software SRL, which also publishes this page. Facts about other apps come from their own privacy policies and app store listings, regulators, courts and independent reviewers, listed under Sources, and were checked on the date shown. Apps change often, so check the current listing before you decide. Flo, Clue and the other names here are trademarks of their owners, who have not reviewed or endorsed this page. None of these apps replaces advice from a doctor or midwife, and Lunation is not a method of contraception.