Millions of people use period tracking apps to understand their bodies, plan pregnancies and monitor their reproductive health. But a recent investigation has found that not all period trackers handle users’ personal information in the same way.
Researchers from the Mozilla Foundation, working with Harvard University’s Berkman Klein Center, examined six of the world’s most popular period tracking apps – Flo, Clue, Stardust, Spot On, Period Calendar and Euki.
Their findings highlight significant differences in how these apps collect, store and process some of the most sensitive information people will ever share.
Here are some of the report’s key findings:
Simply using a period tracker can reveal more than you think
The Mozilla report found significant differences in how apps handled users’ information:
- Many of the apps shared identifiers and technical information with analytics or advertising partners, including services operated by Google, Meta, Microsoft and TikTok
- Mozilla found that Stardust shared detailed reproductive health information, including pregnancy status, contraception, moods, alcohol consumption and symptoms, with a third-party data management company
- The Spot On app itself did not share health information with third parties. However, when users opened certain features that redirected them to the Planned Parenthood website, Mozilla found that the website shared information about the type of healthcare users were seeking with an analytics company
- Even where health information was not shared, simply using a period tracking app may allow advertising or analytics companies to identify that someone is using a reproductive health app.
Privacy protections vary dramatically between apps
One of the report’s biggest findings was just how differently period tracking apps approach privacy.
Some apps keep health information on users’ own devices or provide extensive privacy controls. Others rely more heavily on cloud storage, analytics companies or advertising services to operate and improve their apps.
The researchers concluded that choosing one period tracker over another can make a significant difference to how your personal information is handled.
Privacy claims don't always tell the whole story
The report also warned that privacy claims should be treated with care. Researchers found that some apps marketed themselves as privacy-focused while aspects of their privacy practices raised further questions during testing.
Their advice was simple: don’t rely on marketing claims alone. Check an app’s privacy controls, settings and privacy policy before deciding whether it’s right for you.
Want to know more?
We’ve published a detailed guide explaining:
- What period tracking apps collect
- What the Mozilla investigation found
- Why health data receives extra legal protection
- What the Flo allegations mean for UK users
- What to check before downloading a period tracker.
Read our new guide: Period and fertility tracker privacy
What about the Flo data privacy claim?
Many people never stop to think about what happens to the information they enter into a period tracking app. But this report, together with recent legal action involving the Flo period tracking app has prompted many users to ask important questions about how their health information is collected, used and shared.
If you used the Flo app between 30 June 2016 and 23 February 2019, it’s worth understanding what the allegations involve, what has happened so far and what a potential UK claim could mean for you.
Join the Claim connects consumers with SRA-regulated lawyers. Visit the claim page to check your eligibility if a claim is open with one of our trusted legal partners. If a group action has not yet been launched, you can register your interest and we’ll keep you informed if a partner firm decides to take a claim forward.
