Flo Alternative: The Best Private Period Tracker
Want a Flo alternative that respects your privacy? PeriodOS is an offline period tracker that never leaves your device, compared here with Flo, Clue and Euki.
If you want a Flo alternative that cannot leak your cycle data because it has no server at all, PeriodOS is the pick: a single offline HTML file that keeps every entry in your own browser, for $23 once with no account. Be clear-eyed about the trade, though, because Flo genuinely does more. Its predictions adapt to your logging, its symptom insights are AI-driven, and it has a large anonymous community, none of which an offline file can match. If you want privacy plus a free phone app, Euki stores everything locally too, and Clue is the middle path: still a cloud app, but one held in the EU under GDPR.
| Tool | Best for | Price | Subscription | Works offline |
|---|---|---|---|---|
| PeriodOS | A private, offline Flo alternative | $23 one-time | No | Yes |
| Flo | Predictions, AI insights, community | Free plus premium | Optional | No |
| Clue | Cloud sync under EU privacy law | Free plus Clue Plus | Optional | No |
| Euki | Free, local-only phone tracking | Free | No | Yes |
Why people look for a Flo alternative
Flo is the most popular period app in the world, and for most people it works well. The reason so many search for an alternative is not the features; it is the data. In 2021 the FTC settled with Flo Health over sharing users’ sensitive health information with third parties including Facebook and Google, despite what its policy said at the time. Since 2022, more people have thought harder about where their cycle data is stored and who could request it, and Flo itself responded by adding a free Anonymous Mode. That is a real improvement, but it reduces exposure rather than removing the server.
There are two honest kinds of alternative. The first still uses a cloud server but promises to govern it better, which is where Clue sits with its EU servers and GDPR. The second keeps your data on your own device so there is nothing on a server to breach, sell or hand over, which is where PeriodOS and Euki sit. Deciding between them is really deciding whether you want a company’s promise or an architecture that cannot make that promise necessary.
Flo vs PeriodOS, head to head
These two are opposite answers to the same question, so it is worth being blunt about who wins where.
What Flo does that PeriodOS does not: predictions that adapt as you log more, AI-driven symptom and cycle insights, a pregnancy mode, an anonymous community, partner sharing, a large health-content library, cross-device sync, and push reminders the day before your period. If those features are the reason you track, Flo is better at being Flo, and no offline file will replace them.
What PeriodOS does that Flo does not: it runs with no server, so nothing you type is ever transmitted. There is no account and no email to give. It is a one-time $23 purchase instead of a subscription for the deeper features. It works fully offline after the first load. You can export your entire history as a JSON file and hold it yourself, and it runs on a laptop as comfortably as on a phone.
PeriodOS is a single HTML file with seven sections. Today covers your cycle day and phase, a flow level, symptom chips and a one-word mood. Cycle turns your last period, cycle length and period length into a next-period countdown, an estimated ovulation day, a fertile window and a three-month calendar colored by phase. Flow logs intensity, color and cramping on a 1 to 5 scale and charts the last 30 days. Symptoms is a ten-symptom library with a frequency chart. PMS holds a journal, self-care ritual tags, trigger notes and a record of what helped. History tracks your averages, a cycle-length trend and an editable period log. Settings exports and imports your data so you can back it up.
There is one practical catch worth naming: because PeriodOS keeps everything on the device, there is no automatic cloud backup. If you switch phones or wipe your browser, you move your data yourself by exporting the JSON file and importing it on the new device. That is a small chore Flo handles for you in exchange for holding your data. It is the trade in one sentence.
The honest summary: if you want an app that predicts, reminds and connects you to other people, stay with Flo and use its Anonymous Mode. If you want a private planner you own outright, that keeps your cycle on your device and runs anywhere, PeriodOS is the alternative built for exactly that.
Clue - the middle path
Clue is the alternative for people who want to keep cloud sync but move away from Flo’s track record. It is based in Berlin, holds most user data in Germany, and operates under GDPR, which turns “we protect your data” from a promise into an enforceable right to see and delete it. Clue says it does not sell your data, its design is calm and clinical, and its cycle-science content is genuinely good. The free tier covers period and cycle tracking, and Clue Plus is a yearly subscription, around $40, for deeper analysis.
The thing to understand is that Clue does not remove the server; it governs it. Your data still lives on a company’s systems, and Clue shares some non-health usage data with advertisers unless you opt out. If a cloud account under strong law is acceptable to you, Clue is the best-run version of that. If your goal is no server at all, it is not the answer.
Euki - the free, local-only option
Euki is the closest philosophical cousin to PeriodOS. It is free, open-source and run by a nonprofit, and it stores everything locally on your phone with no cloud and no account. It never asks for identifying information, does not request camera, microphone or location access, and offers a PIN lock and easy data deletion. It also bundles plain-language reproductive-health information and is available in English and Spanish. For a free, privacy-first phone app, it is excellent, and it deserves to be better known.
The difference from PeriodOS comes down to form and ownership. Euki is a free mobile app you install from an app store on iOS or Android. PeriodOS is a $23 HTML file you buy once and own outright, laid out as a dashboard, that runs on a laptop as well as a phone and lets you export and import your data as JSON. If you want free and phone-only, choose Euki. If you want a planner you own and can run anywhere, including a full-size screen, choose PeriodOS. Both keep your data on your device, which is the property that matters.
How to choose
- Pick PeriodOS if you want a private, offline Flo alternative you own outright and can run on a laptop as well as a phone.
- Pick Euki if you want a free, local-only period tracker on your phone and value its built-in reproductive-health resources.
- Pick Clue if you want cloud sync and polished design but prefer your data governed by EU law.
- Stay with Flo if adaptive predictions, reminders and community matter to you more than keeping data off a server.
- Turn on Flo’s Anonymous Mode if you like Flo but want to reduce what is tied to your name.
What “private” actually means here
The word private gets used two different ways, and the difference is the whole point. One meaning is a promise: “we will not sell your data.” That is a policy, and policies can change with a new owner, a new business model or a new law. The other meaning is architectural: there is no server, so there is nothing to sell, leak or subpoena in the first place. PeriodOS and Euki are private in that second, stronger sense. Flo and Clue are private in the first sense, backed in Clue’s case by GDPR.
Neither is wrong, but they are not the same, and it is worth knowing which one you are buying. For the full roundup of cloud and offline options side by side, see our best period tracker apps guide. And if you just want a quick estimate before you commit to anything, our free period calculator gives you a next-period window from your last period and cycle length, with no signup. None of this is medical advice, and no tracker here is birth control.
Frequently asked questions
What is the best private alternative to Flo?
If your priority is that your cycle data cannot leak because there is no server holding it, PeriodOS is the pick: a single offline HTML file that keeps every entry in your own browser for $23, with no account. If you want a free phone app that also stores data only on your device, Euki is the strongest option. Clue is the middle path, a cloud app but one held in the EU under GDPR.
Is PeriodOS as good as Flo?
Not on features, and it does not try to be. Flo has adaptive predictions, AI-driven symptom insights, a pregnancy mode, reminders and a large community that a single offline file cannot match. PeriodOS wins on one thing Flo cannot offer at all: your data never leaves your device, because the app has no server. Pick based on which of those matters more to you.
Does Flo sell my data?
In 2021 the FTC settled with Flo over sharing users' sensitive health information with third parties including Facebook and Google, despite its policy at the time. The settlement required affirmative consent before sharing personal health data and an independent privacy review, and Flo later added a free Anonymous Mode. It is a legitimate app, but its history is exactly why many people look for an alternative.
Is there a free private period tracker?
Yes. Euki is free, open-source and run by a nonprofit, and it stores everything locally on your phone with no account and no cloud. It never asks for identifying information and does not request camera, microphone or location access. If you want free and phone-only, Euki is the answer; PeriodOS is the paid option you own outright and can also run on a laptop.
Can PeriodOS work offline and without an account?
Yes to both. PeriodOS is a single HTML file that runs entirely in your browser, with no login and no server, and it works fully offline after the first load. Everything you type is saved in that device's local storage, so it is your job to back it up, and clearing your browser data will clear the planner.
Does PeriodOS send period reminders like Flo?
No. PeriodOS shows a countdown to your next period when you open it, but it does not send push notifications, because it has no server to send them from. If a phone alert the day before your period is important to you, keep a calendar reminder or stay with a mainstream app for that one job.
Is a private period tracker also birth control?
No. A fertile-window estimate from past cycle lengths is not contraception, and that is true of PeriodOS, Euki and Flo alike. The only app cleared to prevent pregnancy is Natural Cycles, an FDA-cleared device, and even it has a real failure rate. Talk to a clinician before relying on any app for birth control.
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