Clue

Is Clue safe?

Clue is one of the safer period trackers you can pick, mainly because of where it keeps your data and what it promises not to do with it. BioWink, the Berlin company behind the app, stores data on Amazon servers in the EU, says it never shares or sells health data to advertisers, and in June 2024 pledged that it "will never disclose your data to any authority, under any circumstances." We found no privacy fine or order against it. The weak spots are ordinary ones: the app tracks you with device identifiers for advertising, there is no two-step login, and Clue pays nothing for security reports.

We score Clue 68/100, level with Natural Cycles (68) and ahead of Flo (66). Clue says it has 10 million monthly users and passed 1 million paying subscribers in May 2025.

What Clue collects and who sees it

Apple's privacy label for Clue lists health and fitness data, location, contact details, user content, identifiers, usage data and "sensitive info" as linked to you. One item, identifiers, may be used to track you across other companies' apps. On Google Play, Clue says it shares your email address and device IDs with other companies, partly for advertising or marketing, and shares health information for app functionality and personalisation.

The privacy policy, last updated on 29 September 2026, draws the line at health data. It says tracked health data "is never shared with or sold to advertisers, or any partners whose services we may recommend in Clue." What does go to ad firms is the usual measurement data: device IDs, IP addresses, and install and subscription events. Adjust passes standard app events to ad networks such as Meta and TikTok, and Clue buys ads through Apple Search Ads and Google Ads. Social logins with Facebook, Google or Apple exchange no health data, the policy says.

De-identified health data goes to research partners only if you opt in. AI insights run on Amazon Bedrock, and Clue says no data goes to the model's maker.

Does Clue protect your data after Roe v. Wade?

This is where Clue differs most from US-based trackers. Days after the Supreme Court overturned Roe v. Wade in June 2022, Clue said GDPRGDPRThe EU's General Data Protection Regulation, which sets rules on how organisations collect and use personal data and allows large fines.More in the glossary obliges it to protect the tracked data of all users wherever they live, that the data is stored in the EU, and that it had never received a disclosure request from US authorities. It said it would resist one "by all means necessary" and claimed its user data "cannot be subpoenaed from the US." Its 2024 statement went further, with the promise never to disclose data to any authority.

Two cautions. First, the promise is a policy, not something you can check: Clue publishes no transparency report and its privacy policy has no section on legal requests. Second, Clue has no anonymous mode like Flo and Natural Cycles offer, so the data it holds is tied to your account. If your cycle data could be used against you, log only what you need and avoid notes on pregnancy tests or missed periods you would not want read aloud.

How secure is Clue?

Clue says data in transit uses HTTPS, all data stored on AWS is encrypted by Clue, passwords are salted and hashed, and health data is kept separately from profile data. We found no reported breach and no CVE for BioWink in the US vulnerability database.

The gaps are in account protection. We found no two-step login option in Clue's help centre; the closest feature is an app lock that uses your phone's biometrics, which protects the phone, not the account. Clue's security.txt file invites reports to [email protected] but says plainly: "No bug bounty. No payment or reward is offered for any report." Natural Cycles and Flo both pay researchers.

Is Clue a medical device?

Not as you can download it today. The FDA cleared "Clue Birth Control," a contraception mode, through 510(k) K193330 in February 2021, under the product code for contraceptive software apps. But Clue's help centre, updated in September 2026, lists five modes (Period Tracking, Conceive, Tracking, Pregnancy and Perimenopause) and no birth control mode. Clue says it is a registered medical device maker and builds all modes to medical-device standards, but its fertility mode, Clue Conceive, is not FDA cleared and must not be used to prevent pregnancy. The standard period predictions are estimates, not contraception.

How to use Clue more safely

1. Refuse the tracking prompt on iPhone, and turn off ad optimisation and research sharing in Clue's privacy settings.
2. Use a strong, unique password, since there is no second login step. If you signed in with Google, Facebook or Apple, secure that account with two-step login instead.
3. Turn on the app lock, and on a shared phone change the app icon or hide the app.
4. Do not rely on period predictions or Clue Conceive to avoid pregnancy; talk to a doctor or pharmacist about contraception.
5. Before you delete your account, email [email protected] for a copy of your data. Deletion is permanent.

How we scored it

The regulatory record (88) is Clue's strongest factor: no fine or order, though no regulator has reviewed a feature the app offers today. Privacy (62) and security (62) are its weakest, held down by ad tracking through identifiers, no two-step login and no bug bounty, against the credit of EU storage and a firm line on health data. Scams and harmful content (78) is high because there is little contact with strangers.