Clue

A period-tracking app made by a German team, with strict privacy specs and medically vetted content

Freemium DE

Clue is a period- and cycle-tracking app developed by Berlin company Biowink, with over 100 million downloads accumulated, covering 190+ countries, predicting cycles with algorithms and providing medically grounded educational content.

Features and application scenarios

Among a pile of period apps, Clue's recognizability comes from two things: content quality and its privacy stance. Its educational content is written and reviewed by a professional team and doesn't take the path of making physiological phenomena sound mysterious; and as a German company, it's subject to the EU's GDPR, the world's strictest personal-data norm, so for users who care whether "my period data will be sold or subpoenaed," this country of registration is itself a kind of protection — especially after many US states tightened reproductive rights, the data ownership of period apps has become a real privacy issue. Feature-wise, it covers the whole life cycle: basic period tracking, Clue Plus advanced insights, Clue Conceive conception mode, pregnancy mode, perimenopause tracking, and even supports the scenario of "no period but still needing to track the cycle." For prediction, it uses algorithms to analyze personal historical data, and starting November 2024 introduced a prediction feature strengthened with anonymized data. The basic version is free; advanced features use a subscription.

Suited to anyone needing to track their menstrual cycle, from menarche, conception, and pregnancy to perimenopause; especially suited to users who value data privacy and don't want to hand physiological data to an ad-model app.

Main features

Period and cycle tracking, basic features free
Ovulation and fertile-window prediction
Symptom and mood-pattern logging
Clue Plus subscription: advanced insights and analysis
Clue Conceive conception mode and pregnancy mode
Perimenopause tracking
Clue Connect: share data with a partner
Wearable integration and professionally reviewed educational content

Common uses

Daily tracking of period and symptom changes
Grasping the fertile window when trying to conceive
Recording symptoms for OB-GYN visit reference
Tracking body changes in perimenopause
Syncing cycle info with a partner

Key Features

Period and cycle tracking, basic features free
Ovulation and fertile-window prediction
Symptom and mood-pattern logging
Clue Plus subscription: advanced insights and analysis
Clue Conceive conception mode and pregnancy mode
Perimenopause tracking
Clue Connect: share data with a partner
Wearable integration and professionally reviewed educational content

Pros

A German company subject to GDPR, with strict privacy norms
Educational content is professionally vetted, not pseudoscience
Covers the complete life stages from menarche to perimenopause
Basic features are free to use; paying isn't necessary

Cons

Prediction is mainly algorithm-based, with a less prominent AI degree than AI-focused competitors
Advanced insights require a Clue Plus subscription
Cycle prediction has limited accuracy for those with very irregular cycles
Traditional-Chinese content richness isn't as good as the English version

Use Cases

Daily tracking of period and symptom changes
Grasping the fertile window when trying to conceive
Recording symptoms for OB-GYN visit reference
Tracking body changes in perimenopause
Syncing cycle info with a partner

Editor's Note

For the period-app category, I think the selection criterion should be reversed: not who has more features, but who least wants your data. Clue's German background and GDPR applicability is a real plus on this. As for how accurate the prediction is, frankly all such apps are the same — the body isn't a clock, and treating it as a recording tool is more useful than treating it as an oracle.

FAQ

Can Clue be used as a contraceptive method?

No. Clue's prediction is a reference range estimated from historical data and isn't a medical-device-certified contraceptive method. There are indeed apps FDA-certified for contraception (like Natural Cycles), but that's another level of product and regulation, and the two can't be conflated.

Is my period data safe?

Clue is a German company subject to GDPR, on the stricter end of privacy norms, which is also why many people choose it. But any cloud app has data risk, so if you're extremely concerned, you can evaluate whether to use a local-storage alternative.

Is it accurate for people with irregular cycles?

Accuracy drops noticeably — a common limit of all cycle-prediction apps, since the algorithm needs regular historical data to estimate. If the cycle is long-term disordered, the app's value mainly lies in 'fully recording symptoms for the doctor' rather than trusting its predicted dates.