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Looking for something other than Flo or Clue?

People leave for four reasons: privacy, subscription fatigue, feature bloat, or no measurement — the first three have plenty of answers, the fourth barely any. A fair word on the two you're leaving: far more people are testing them than anything below, and Clue's 8/10 is the highest Mozilla privacy score of any mainstream app in the review. If you want prediction tuned on an enormous number of cycles, or pregnancy coverage in the same app, staying put is a defensible answer.

Worried your period data isn't safe?

That worry has a specific case behind it, and it is worth knowing exactly what it did and didn't decide. In Frasco v. Flo Health, Inc., No. 21-cv-00757-JD (N.D. Cal.), the verdict form signed on 1 August 2025 found that Meta intentionally recorded plaintiffs' communications, that they had a reasonable expectation of privacy, and that Meta did not have the consent of all parties. Two things matter here: the questions the jury answered were about Meta, not Flo, and the conduct at issue runs from 2016 to 2019, so it is not a description of the app you would install today. It is also a jury verdict, not a final judgment — Meta moved to decertify the class on 11 August 2025, and the separate class settlement with Flo Health has a fairness hearing set for 29 October 2026.

How they compare

Ratings and update dates read off the US App Store on 11 August 2026 (Mensinator isn't on the App Store — version and date from its F-Droid page, same day); privacy scores from the Mozilla Foundation's review of period and ovulation trackers, published 16 July 2026; licences from F-Droid and the projects' own sites. The best privacy score belongs to the app that has gone longest without an update, and the app updated most recently has the worst one.

Each one, in detail

1. drip (open source, GPL-3.0, free) — Built by Heart of Code e.V., a Berlin non-profit. Data stays on the device, the source is on GitLab, and it supports the symptothermal method — the privacy claim is one you can check rather than accept. The cost is scale: 56 ratings, and a Mastodon account with 619 followers and 94 posts in total. A small volunteer project; choose it knowing that.
2. Euki (free, no in-app purchases) — The highest privacy score in Mozilla's review, 10/10. Non-profit and open source; the listing describes a customisable PIN, data stored locally and nowhere else, and reproductive-health information alongside the tracking. Weigh that against the update date in the table — an unmaintained app eventually meets an OS version that disagrees with it.
3. Mensinator (open source, MIT, Android only) — The practical answer to "I want to leave but not lose four years of logs": version 2.1 added importing from Flo and Clue. No sign-up, no cloud, data on the device, home-screen widget. Two limits: Android only, and it's on F-Droid rather than a store you already have open.
4. Period Calendar (free download, closed source) — The mainstream option, and the highest star average in the table. Its listing says no registration is needed and data stays on the device; Mozilla still scored it 6/10, below Clue and above Flo. The softest landing if you want fewer moving parts rather than a privacy audit.
5. Spot On (Planned Parenthood Direct, free) — Birth control first: method-specific reminders and guidance, with period and fertile-window prediction alongside. Worth a look if your app buried contraception under everything else — and its star average is the lowest of the mainstream apps in the table.
6. Stardust (free download, closed source) — Where a lot of people actually go, and the most recent update of anything here. Its listing describes blending science, "ancient wisdom", astronomy and AI. But 2/10 with Mozilla, the lowest in that review: if privacy is your reason for leaving Flo, this moves you in the wrong direction.

If privacy is the reason, drip, Euki and Mensinator are the answer — each asking you to accept a smaller, slower app. If it's cost or clutter, Period Calendar, Spot On and Stardust are the softer landing.

Have you ever thought about how much you actually bleed?

Every app above, Flo and Clue included, records flow as light, medium or heavy. Millilitres have historically lived in clinical tools like the PBAC, not consumer apps, and the figure usually quoted as the heavy-bleeding line is 80 ml per cycle.

PeriodVol exists for that one gap. You tap the picture of what you used — pad, tampon or cup — and how soaked it was; it estimates volume in millilitres per day and per cycle and flags a cycle that crosses 80 ml. How those estimates are calculated, and where they stop being reliable, is on its methodology page. The app is free to use, with one optional one-time purchase — US$2.99, not a subscription.

Three caveats. PeriodVol is not a medical device and diagnoses nothing; 80 ml is a reference line, and what the app does is leave you with numbers and dates for the appointment instead of "I think it's a lot". It is closed source and paid, so on the privacy axis specifically drip and Euki beat it — their code can be read and PeriodVol's cannot. And an estimate from what you used is an estimate: a menstrual cup with markings on it is more accurate than any app.

If it's the appointment you're preparing for, our guide to what the health authorities actually count as a heavy period lines up which measure each organisation leads with, and is more useful than any app comparison.

FAQ

What is the ranking based on?

How verifiable the switch is, then how well maintained the app is. Open-source, local-first apps whose claims anyone can check sit at the top; mainstream apps follow, ordered by Mozilla privacy score. It is not a ranking of prediction accuracy — we did not run the same cycle history through all six and compare the forecasts.

Is Euki safe to use if it hasn't been updated?

Nothing in an app breaks on a schedule, and its privacy design doesn't decay. But its last release was 4 September 2025, and unmaintained apps eventually collide with an OS update, a changed permission model, or a bug nobody is left to fix. That's information, not a verdict.

Does any of this diagnose anything?

No. This page compares apps, not health. Every app here, and this guide, is not a medical device and not medical advice. If your bleeding worries you, that conversation belongs with a doctor — and the more specific your record, the shorter the conversation.