Most period tracking apps collect far more data than you’d expect, and only a handful handle that information safely. The Mozilla Foundation, which independently reviews consumer apps for privacy, found that the majority of popular period trackers failed to meet minimum security standards. Only two, Euki and Clue, passed. If you’re looking for a safe option, those are strong starting points, but the full picture involves understanding what makes an app risky and what you can do to protect yourself regardless of which app you choose.
Why Period Tracker Privacy Matters
Period tracking apps collect information on far more than your cycle dates. A University of Cambridge report described menstrual app data as a “gold mine” for consumer profiling, noting that these apps gather details on exercise, diet, medication, sexual preferences, hormone levels, and contraception use. All of that feeds into a profile that advertisers, data brokers, and potentially employers or insurers can access.
The financial incentive is real. According to Privacy International, a pregnant customer’s data is worth roughly $1.50 to advertisers, compared to $0.10 for a non-pregnant person. Apps also track mood data, which lets advertisers target users during vulnerable emotional states. Beyond advertising, there are legal concerns: in a post-Dobbs landscape, reproductive health data stored on company servers could theoretically be subpoenaed by law enforcement.
Apps With Strong Privacy Records
Mozilla’s “Privacy Not Included” guide is one of the most reliable independent assessments available. Of the period and ovulation trackers they reviewed, only Euki and Clue met their minimum security standards. Every other major app received a warning label.
Euki, developed by the reproductive health organization Ibis, stores data locally on your device rather than on a remote server. That means no company holds a copy of your cycle history. It also includes a fake “secondary screen” you can set up in case someone else accesses your phone.
Clue, based in Berlin and subject to European data protection law (GDPR), has a relatively strong track record. The company did previously send usage data to Facebook but publicly announced it would stop. Because Clue operates under European jurisdiction, it faces stricter legal requirements around data handling than most U.S.-based apps.
Two other apps frequently appear on privacy-focused recommendation lists: Drip, an open-source Android app where you can inspect the actual code, and Stardust, which announced itself as the first period tracker to offer end-to-end encryption for all users. End-to-end encryption means that even if the company receives a government subpoena, it cannot hand over your tracking data because the information is unreadable to anyone but you.
Apps That Failed Privacy Reviews
Mozilla flagged several widely used apps for poor data practices. The list includes Flo, Period Tracker by GP International, Ovia Fertility, Ovia Pregnancy, My Calendar Period Tracker, Pregnancy+ by Philips, WebMD Pregnancy, and Pregnancy & Due Date Tracker by Wachanga.
Flo is the most prominent name on that list, with over 100 million users. In 2021, the company settled with the U.S. Federal Trade Commission over allegations that it repeatedly shared users’ health information with third-party advertisers, including Facebook and Google, despite explicitly promising not to. Ovia had a different but equally troubling problem: in 2019, it was found to be marketing user data to employers and health insurers, letting companies see how many workers were using fertility functions and when new parents planned to return to work. That kind of corporate surveillance opens the door to workplace discrimination and changes in health coverage.
What Makes an App Safer
Three technical features separate privacy-respecting apps from the rest.
- Local-only storage: Apps that keep your data on your phone, not on company servers, eliminate the biggest risk. If a company doesn’t hold your data, it can’t sell it, lose it in a breach, or hand it over to law enforcement. The tradeoff is that if you lose your phone, your data is gone.
- End-to-end encryption: If an app does sync to the cloud, encryption that only you can unlock is the next best thing. Stardust’s implementation means even the company itself cannot view your cycle data.
- Open-source code: Apps like Drip publish their source code publicly, so independent developers and security researchers can verify that the app does what it claims. Closed-source apps require you to trust the company’s word.
No single feature guarantees safety, but an app that combines local storage or strong encryption with no third-party advertising trackers is a fundamentally different product from one that embeds Facebook’s tracking tools into its code.
How to Protect Yourself in Any App
If you already use Flo and don’t want to switch, the company developed an “Anonymous Mode” feature after the Dobbs decision. Activating it strips your name, email address, and technical identifiers from your account. If Flo receives an official request to identify you, anonymous mode prevents the company from connecting your data to your identity. The limitation is that you lose personalization features, and you won’t be able to recover your data if your phone is lost or replaced.
For any app, a few practical steps reduce your exposure:
- Use a burner email. Sign up with an email address that isn’t tied to your real name. This breaks the link between your identity and your cycle data even if the company’s privacy practices are weaker than advertised.
- Deny unnecessary permissions. Period trackers don’t need access to your location, contacts, or photos. If an app asks for those, decline.
- Delete your account when you’re done. Some apps, like Period Tracker by GP International, let you delete your account and all online backups immediately through the settings menu with no waiting period. Others may retain data for weeks or months. Check the app’s data deletion policy before assuming your information is gone.
- Turn off cloud backup. If you’re comfortable with the risk of losing data if your phone breaks, disabling cloud sync keeps your information off company servers entirely.
The Simplest Safe Option
If privacy is your top priority and you don’t need advanced features like fertility predictions or community forums, the safest approach is the lowest-tech one: a simple calendar app or paper journal. No data leaves your hands, no company can be compelled to share it, and no breach can expose it.
For those who want the convenience of a dedicated tracker, Euki offers the best combination of local-only storage and privacy-first design. Clue is a solid choice if you want cloud sync with European legal protections. And Stardust or Drip are worth considering if end-to-end encryption or open-source transparency matter most to you. The common thread among all of these is that they were built, or rebuilt, with the understanding that menstrual data is sensitive health information, not an advertising product.