Period Tracker That Doesn’t Sell Data: 6 Apps Tested
An independent privacy team tested six trackers this summer. Here is what they found, app by app, and how to check any tracker yourself in five minutes.
A period tracker that doesn’t sell data does exist, and in July 2026 an independent privacy team put names and scores on the question: Mozilla Foundation tested six popular period trackers hands-on and found one that kept everything on the device, several that shared app or symptom data with third-party analytics and ad services, and a wide gap in how much control each app gives you. This guide lays out those results app by app, explains what “selling data” actually looks like in this category (it is usually sharing, not a sale), and gives you a five-minute check you can run on any tracker, including ours.
Is there a period tracker that doesn’t sell data?
Yes. Mozilla Foundation’s July 2026 investigation, run by privacy researcher Shoshana Wodinsky with manual testing and network analysis, found that Euki kept the health data entered during testing on the device, with no account required and no third-party data collection around its core tracking features. It scored 10 out of 10, the only perfect result in the set.
The more useful finding is what “doesn’t sell data” really means here. Mozilla did not describe any of the six apps as literally selling your cycle data. What it documented was sharing: app and device data sent to advertising and analytics partners, symptom data sent to third-party analytics services, and in one case data flowing out before the user had entered anything. If you are scanning best period tracker app privacy lists, that distinction is the one to hold onto: the question is where your data goes, who can see it, and whether you can stop it.
What Mozilla found, app by app
Six apps, one tester, the same method for each. Here are the scores and the finding that matters most from each review.
Two of these are worth reading in full before you choose: the Euki review, for what a genuinely local-first tracker looks like, and the Stardust review, for what data leaving a tracker actually looks like in a network trace.
Period tracker privacy: the four things Mozilla says to check
Mozilla’s roundup closes with four findings that apply to every tracker, including the ones not in its test. They are the basis of the checklist below.
How to check any period tracker in five minutes
You do not need a network analyzer to apply what Mozilla learned. Five checks at setup tell you most of what you need.
Where Otty stands
Otty was not in Mozilla’s test, so we will not give ourselves a score. Here is our design, stated as fact and checkable in our privacy policy: your cycle data is stored on your device by default, sign-in is optional and only needed for cloud backup and partner pairing, we do not sell your personal information to any third party, Apple Health access is read-only and limited to menstrual flow, and partner sharing is opt-in, item by item, and revocable from Settings. Our service providers are named in the policy rather than hidden behind “trusted partners.”
The honest limits: Otty does use analytics and crash-reporting providers to run the app, and if you choose to sign in, your data is backed up to cloud infrastructure. Neither is a secret, and both are in the policy. If you want a tracker where nothing ever leaves the phone under any setting, Euki is the app Mozilla points to. If you want a couples tracker whose default is on-device and whose sharing you control item by item, that is what we built, and the fuller comparison of the couples options, privacy scores included, is in our guide to the best period tracker for couples.
A good privacy policy names its providers and its limits. A marketing page names its adjectives.
Which private tracker fits which person
The right answer depends on what you are tracking for. For privacy above everything, on a single phone, Mozilla’s evidence points to Euki. For a clinically minded tracker with unusually granular sharing controls, Clue, with the caveat that its ad sharing is opt-out. If you are leaving Flo specifically, our lane-by-lane guide to alternatives to Flo takes each option on what it does better than Flo and where it falls short. For a couple who want one person’s cycle shared with a partner on purpose, the couples options trade a little isolation for a shared view; how Otty compares on that trade lives in Clue Connect vs Otty and Flo for Partners vs Otty, and the mechanics of sharing safely are on our share your cycle with your partner page.
Period tracker privacy FAQ
The takeaway on finding a period tracker that doesn’t sell data: trust the network trace over the marketing, look for on-device storage, optional accounts, and opt-in sharing you can revisit, and read the one page every app has to publish. Mozilla did the hard part in July 2026; the five-minute check above does the rest.
