Mozilla report finds privacy risks in popular period‑tracking apps

Mozilla, together with researchers from Harvard’s Berkman Klein Center and the University of Illinois, evaluated the privacy practices of six widely used period‑tracking applications – Stardust, Flo, Clue, Spot On, Period Calendar and Euki. The assessment graded each app on how it collects, stores and shares sensitive reproductive‑health data.

Stardust received the lowest score, sharing detailed cycle dates, symptoms and pregnancy status with the data‑management firm RudderStack – a partner not mentioned in its privacy policy. A spokesperson said the data are sent only to analysis tools and cannot identify users, but experts warn that each additional intermediary raises the risk of leaks or legal requisition, especially after the U.S. Supreme Court’s 2022 overturn of Roe v. Wade.

Euki earned a perfect rating, keeping all information locally on the device and requiring no user account. Flo scored moderately high, while Period Calendar was noted for sending device details to Google and InMobi. Spot On, developed by Planned Parenthood, was secure within the app but leaked data via its integrated web browser.

Mozilla’s report highlights growing concerns that reproductive‑health apps could provide evidence in legal actions against women seeking abortions, underscoring the need for clearer data‑privacy protections.