The privacy question with a period tracker is not whether the app promises encryption. It is whether the cycle data ever leaves the phone at all, and if it does, who holds the keys, which jurisdiction stores the backup, and what happens to the record when a subpoena arrives. Four years on from Dobbs, that question has stopped being theoretical: prosecutors in several US states have subpoenaed cycle data in miscarriage-related cases, the FTC has fined multiple tracking apps for undisclosed data-broker sharing, and the ACLU keeps a public list of trackers to avoid. This guide covers seven Android apps that answer the question honestly.
We tested each app over two cycles on a Pixel 8 and a Galaxy S24, watching network traffic with mitmproxy, reading the privacy policy and terms of service in full, checking the ACLU’s tracker roster, and cross-referencing with Mozilla’s Privacy Not Included database. The ranking is not about UI polish or wearables integration. It is about where the data goes.
What privacy actually means in a period tracker
Five things to check before you install any tracker:
- Where does the data live? On-device only means the record never touches a server. Cloud sync means someone else holds a copy. Ask before you download.
- Is an account required? An email or phone number ties the cycle log to your identity. Apps that skip the account entirely cannot hand over what they do not have.
- What is the third-party sharing policy? The FTC settled with Flo in 2021 for sharing cycle data with Facebook, Google Analytics, and AppsFlyer. Read the current policy, not the marketing page.
- Is the code open? Open-source lets independent researchers verify the privacy claims. Closed-source means you trust the vendor.
- Where is the company incorporated? EU-based companies fall under GDPR. US-based companies fall under state subpoenas. The jurisdiction changes what the vendor can be compelled to hand over.
Quick comparison
| App | Best for | Data location | Free plan | Starting price/mo | Open source |
|---|---|---|---|---|---|
| Euki | On-device only tracking | Local only | Yes, full | Free forever | Yes |
| drip. | Fully open-source pick | Local only | Yes, full | Free forever | Yes |
| Periodical | Minimal F-Droid tracker | Local only | Yes, full | Free forever | Yes |
| Stardust | Encrypted mainstream option | Cloud (encrypted, US) | Yes, ad-free | $9.99/mo Premium | No |
| Clue | GDPR-protected mainstream | Cloud (encrypted, Germany) | Yes, basic | $9.99/mo Plus | No |
| Natural Cycles | FDA-cleared contraception | Cloud (encrypted, Sweden) | 30-day trial | $12.99/mo | No |
| Blood by Pslove | Minimal-scope tracker | Cloud (encrypted, Singapore) | Yes, ad-free | $2.99/mo Premium | No |
The 7 best privacy-focused period tracker apps for Android
1. Euki, best on-device-only tracker
Euki is built by Women Help Women, an international non-profit that provides reproductive-health information and abortion support. It is the pick the ACLU points to first: no account, no email, no phone number, no server. The cycle record, symptoms, and appointments live inside the app on the phone, and nothing leaves. A PIN code locks the app, and a data-sweep feature clears everything on a schedule you set, including a panic-wipe option that reads as blank calendar to anyone who opens it.
The app is more than a tracker. It ships a peer-reviewed content library on contraception, abortion, and STIs, and a beta care-navigator directory of clinics and telehealth providers, both vetted by health experts. The Google Play listing verifies the no-data-collection claim in the Data Safety section, which is the only place Google forces a legal disclosure.
Where it falls short: the design skews utilitarian and the interface has fewer visualisations than the paid apps. Predictions get more accurate the longer you track, but the first two cycles are approximate. There is no wearable sync.
Pricing:
- Free: everything, forever, funded by non-profit grants
- Paid: none
Platforms: Android, iOS
Bottom line: the strongest privacy option available on any platform. Pick this if the only requirement is that the cycle log never leaves the phone.
2. drip., best fully open-source pick
drip. is a Berlin-based project run by a feminist collective, funded by grants and donations, licensed under the AGPL. Every line of code is on GitHub, network traffic monitors show zero server calls in normal use, and the app has never carried an ad. Data stays on the device unless the user manually exports an encrypted backup. The German incorporation means it operates under GDPR, but the point is that GDPR barely matters here since there is no server to compel.
The app supports symptom tracking, temperature and cervical mucus logging (for fertility awareness), and multiple prediction methods including calendar, symptothermal, and a customisable “NFP” mode with configurable rules. It ships without wearables integration deliberately: the collective’s stance is that any third-party sync creates a new data-egress path.
Where it falls short: the app is Android-only on Google Play (iOS users install through TestFlight or wait for the App Store review), and there is no Wear OS complication. Predictions are conservative by design, not optimistic.
Pricing:
- Free: everything, forever, no ads, no in-app purchases
- Paid: none
Platforms: Android (also on iOS via TestFlight)
Bottom line: pick this if verifiable open-source matters more than convenience. The absence of a server is not a marketing promise, it is architecturally impossible for drip. to send data anywhere.
3. Periodical, best minimal open-source pick
Periodical is a stripped-back Android period tracker maintained on GitHub since 2013, distributed exclusively through F-Droid. It does one thing: log periods, predict the next one, and optionally track basic symptoms. No account, no cloud, no ads, no permissions beyond storage for encrypted backups. The APK is a few megabytes and the interface is deliberately spartan.
The choice between drip. and Periodical comes down to fertility-awareness support. Periodical does calendar predictions only, drip. does full symptothermal method. For anyone who only needs “when is my next period” and treats a period tracker as a utility, Periodical is the smaller, faster, no-nonsense option.
Where it falls short: no symptothermal or basal-temperature method, no rich symptom taxonomy, no localisation into every language. It is designed for a specific use case and does not stretch.
Pricing:
- Free: everything, GPL-licensed
- Paid: none
Platforms: Android (F-Droid only)
Bottom line: the pick if the whole use case is a simple next-period prediction and the phone already has F-Droid installed.
4. Stardust, best encrypted mainstream option
Stardust went viral on TikTok in 2022 after positioning itself as the anti-Flo, and it has kept the privacy angle central. The app is founded and led by women, encrypts stored data, and states clearly in its policy that it does not sell or share personal health information. It is closed-source and does back cycle logs up to its own servers in the US, so the privacy story is a step below Euki or drip., but it is auditable enough that Mozilla’s Privacy Not Included list marked it acceptable.
The user experience is where Stardust wins mainstream users: it blends cycle science with astrology and moon-phase overlays, has clean visualisations, supports partner-sharing (opt-in, encrypted), and includes fertility and pregnancy modes. For anyone who wants a mainstream app aesthetic without Flo’s or Ovia’s track record, this is the pick.
Where it falls short: US incorporation means the company can be compelled to hand over data under a subpoena. Cloud storage is required for the app to function fully. The premium tier gates content that reads as core to the experience.
Pricing:
- Free: full tracking, ad-free, most predictions
- Paid: $9.99/mo Premium (or $59.99/yr) unlocks advanced hormone insights, deeper astrology, and partner mode
Platforms: Android, iOS
Bottom line: the polished mainstream pick for anyone who wants Instagram-level design and can accept US-jurisdiction cloud storage.
5. Clue, best GDPR-protected mainstream option
Clue is the tracker built by BioWink in Berlin, in operation since 2013, incorporated under German law and therefore governed by GDPR. That matters: GDPR requires explicit consent for any secondary use of health data, gives users a legal right to demand deletion, and gives European regulators authority to fine any vendor that shares data without a lawful basis. The clinical-research collaborations Clue publishes are peer-reviewed with universities, not marketing white papers.
The app is polished, tracks over 200 factors beyond bleeding (mood, sleep, sex drive, energy, skin, digestion), supports Oura, WHOOP, Fitbit and Apple Health sync, and covers cycle, fertility, pregnancy, and perimenopause. It does back up to Clue’s servers, but the German jurisdiction and GDPR compliance make that materially different from a US-based competitor.
Where it falls short: the free tier is more limited than it used to be. Advanced ovulation, cycle-phase alerts, and full perimenopause tools sit behind Clue Plus. And a US-resident user should note that GDPR does not apply to a subpoena originating in the US, though data-transfer restrictions can add friction.
Pricing:
- Free: period, symptom, and basic ovulation tracking with birth-control reminders
- Paid: $9.99/mo Clue Plus (or $39.99/yr) for advanced ovulation, pregnancy tools, and perimenopause tracking
Platforms: Android, iOS, Wear OS, Apple Watch
Bottom line: the pick for EU residents and anyone who values GDPR-backed rights over the extra step of a fully on-device app.
6. Natural Cycles, best FDA-cleared for cycle-awareness contraception
Natural Cycles is the only tracker on this list that is CE-marked in Europe and FDA-cleared in the US as a Class II medical device for use as contraception. It uses basal body temperature (via NC° Band, Apple Watch Series 8 or newer, Oura, or a compatible Garmin) plus cycle logs to compute a daily “red day” or “green day” reading, with a Pearl Index of 93 percent typical-use and 98 percent perfect-use effectiveness. That regulatory clearance is unique on Android in 2026.
The company is Swedish, headquartered in Stockholm, and operates under GDPR plus MDR (EU Medical Device Regulation). Data is encrypted in transit and at rest, and the app markets its privacy features prominently because the business model is subscription revenue, not data brokerage.
Where it falls short: subscription-only, no genuine free tier past a short trial. Requires a compatible thermometer or wearable to reach the advertised effectiveness. The 93 percent typical-use figure is materially lower than IUDs or implants, and the app is not a barrier method against STIs.
Pricing:
- Free: 30-day trial
- Paid: $12.99/mo month-to-month, or $99.99/yr (works out to $8.33/mo), NC° Band included with annual plan
Platforms: Android, iOS, Wear OS, Apple Watch, Oura, Garmin
Bottom line: the pick when you want cycle-awareness contraception with a regulator behind the effectiveness claim, and you own or plan to buy a wearable.
7. Blood by Pslove, best ad-free minimal-scope tracker
Blood is a Singapore-built tracker that markets itself on avatar customisation and low-friction daily logging. Privacy is not the front-page pitch, but the Data Safety card discloses limited sharing, the app runs ad-free even on the free tier, and it does not require an account for basic use. The Singaporean incorporation puts the company under the PDPA regime, which is less permissive than the US model on secondary data use.
The interface is aimed at first-time trackers and teens, with playful avatars that reflect logged mood. Symptom taxonomy is smaller than Clue’s but broader than Periodical’s. The free tier does not gate the tracking or predictions themselves — the paid tier unlocks avatar cosmetics, richer content, and calendar sync.
Where it falls short: the app leans heavily on gamified avatars, which reads as juvenile for users past their mid-twenties. Some content and premium visualisations gate behind subscription. The clinical validation is not on the level of Clue or Natural Cycles.
Pricing:
- Free: full tracking, symptom log, predictions, ad-free
- Paid: $2.99/mo Premium (or $19.99/yr) unlocks avatars, deeper content, and third-party calendar sync
Platforms: Android, iOS
Bottom line: the pick for a first tracker where a low-cost premium tier is fine and the aesthetic matches a younger user.
How to pick the right one
Match the privacy posture to your risk model:
- If you live in a US state with an active abortion prosecution history: Euki or drip., in that order. The rule is that no cloud copy exists.
- If you want the simplest possible tracker with no cloud: Periodical if you already use F-Droid, Euki otherwise.
- If you want mainstream design without Flo or Ovia baggage: Stardust first, Clue second.
- If you want GDPR-backed rights and clinical-research provenance: Clue.
- If you want cycle-awareness as birth control with regulatory backing: Natural Cycles, with the caveat about typical-use effectiveness.
- If a partner or teen is using the tracker and the avatar-first design fits: Blood.
- If you use Flo, Ovia, Glow, or any tracker that showed up on the FTC or ACLU list: uninstall it, request account deletion in writing, and pick a replacement from the list above.
FAQ
Which period tracker is the safest for privacy?
Euki is the strongest option. It does not require an account, does not sync to any server, and is built by a reproductive-health non-profit with the ACLU’s endorsement. drip. is a comparable pick if verifiable open-source is the requirement.
Can police get my period tracker data?
In the US, yes, in most cases, unless the data never left the device. Any app that syncs to a cloud server can be compelled by subpoena or search warrant. On-device-only apps like Euki, drip., and Periodical cannot produce data they never stored.
Are open-source period trackers actually private?
The code being open is not by itself a privacy guarantee, but it means independent researchers can verify the claims. drip. and Periodical have both been audited by third parties. Euki is also open-source.
Is Apple Health more private than a third-party app?
Apple Health stores cycle data on the device by default and only syncs to iCloud with the user’s explicit consent (with end-to-end encryption enabled in Advanced Data Protection). It is a reasonable privacy option on iOS. This guide focuses on Android.
What happened with Flo and Facebook?
The FTC settled with Flo in 2021 over allegations that the app shared user data, including whether a user was pregnant, with Facebook, Google Analytics, and AppsFlyer without adequate disclosure. Flo has since added an “Anonymous Mode”, but the historical record is public. Full details are on the FTC settlement page.
Are any of these covered by HIPAA?
Consumer period tracker apps are generally not covered by HIPAA in the US, which only applies to healthcare providers, insurers, and their business associates. That is why on-device-only or GDPR-jurisdiction apps matter — a HIPAA gap does not exist if the data never leaves the phone or the vendor is bound by stricter EU law.
