Flo vs Clue: which period tracker is better?

Pick Clue if privacy is why you’re asking. Pick Flo if you want the most from a free app and don’t mind turning on its privacy settings yourself. Both are good period trackers with big user bases. Flo has about 2 million ratings on the US App Store at 4.7 stars, and Clue has about 406,000 at 4.8. Both predict your period and fertile window for free and charge a subscription for the rest. The real differences are where your data goes, what you have to pay for, and how each one handles a cycle that won’t behave.

We make Plum, a third period tracker, so weigh this page with that in mind. Every claim about Flo and Clue below comes from the company’s own site, help centre, privacy policy or App Store listing, and we read them all on October 12, 2026.

Flo vs Clue at a glance

Is Flo or Clue free?

Both are, for the basics, and Flo’s free tier is the bigger one. Its help centre lists period and ovulation predictions, more than 80 symptoms to log, custom reminders, an anonymous community called Secret Chats, Anonymous Mode and basic partner sharing. Flo Premium adds daily insight stories, the article and video library, a chatbot it calls the Health Assistant, symptom patterns, a symptom checker and a doctor’s report. The free version comes with nudges, and Flo’s own help page says to expect Premium offers as splash screens, pop-ups and push notifications.

Clue says a free version will always exist, and it covers tracking and the core predictions. Clue Plus holds a lot that Flo gives away or doesn’t have. That includes forecasts up to 12 months ahead, cramp predictions, the full article tab, extra charts, Clue Connect sharing, the conceive and perimenopause modes, and syncing with an Apple Watch, Oura or Whoop.

Prices change by country, so check the store before you pay. On the US listing Clue Plus was $9.99 a month or $39.99 a year. Flo’s listing showed a spread of Premium prices from $1.99 to $59.99, which reflects intro offers and plan lengths. Flo’s help centre says most offers start with a free trial you can use once, and it renews into a paid plan unless you cancel at least 24 hours before.

How do Flo and Clue predict your period?

Both work from the dates you log, and both want about three cycles before they’re confident. Clue bases predictions on your last 12 cycles and its averages on the last six. It puts ovulation 13 days before your next predicted period, and moves it if you log a positive ovulation test or temperature. Its help centre says three past cycles are enough for core predictions, and more if your cycles are irregular.

Flo asks for the last 12 months of periods, or at least three cycles. It uses your logged symptoms as well as your dates. Instead of flagging a late period the day after it was due, Flo builds a window of likely days and only shows a delay once that window closes. That’s why the prediction can seem to slide forward a day at a time. Our page on how accurate period tracker apps are explains why neither approach beats the other on a regular cycle.

Which is better for irregular periods?

Clue, though not by much. Its biggest help is that you can hide atypical cycles from its calculations. A month thrown off by illness, travel or emergency contraception then stops dragging every later forecast. Clue also has a perimenopause mode, which needs Clue Plus, and a mode for people with no period at all.

Flo’s answer is to show its doubt. When you’ve logged fewer than three cycles or your cycles vary a lot, it stretches the fertile window from seven days to as many as 14. That’s honest, but you get no way to tell it which months to ignore. If your cycles swing widely, as they often do with PCOS or in perimenopause, no app will pin the date. The irregular period calculator gives you a range from your own history instead.

Is Clue more private than Flo?

Yes, on the record and on the labels. In January 2021 the US Federal Trade Commission announced a settlement with Flo Health. It alleged that Flo had promised to keep health data private and then passed details such as pregnancy to marketing and analytics services, including Facebook’s and Google’s. Under the settlement, Flo had to get consent before sharing health data, have its privacy practices reviewed independently and tell affected users. Our guide to whether Flo sells your data covers the case and what followed it.

Flo today is a different company on paper. Its privacy policy says it will never sell your data and doesn’t share health data with third parties for advertising. Your advertising ID only goes to its marketing partners if you allow tracking. Flo also built Anonymous Mode, which it sped up after the Supreme Court overturned Roe v. Wade. It strips your name, email and IP address from your health data so Flo can’t tell the data is yours. It’s free, but it’s permanent, it won’t sync to a new phone, and it turns off Flo for Partners.

Clue’s privacy policy says your data sits on servers in the EU and that the health data you track is never shared with or sold to advertisers. Its help centre goes further, saying Clue won’t comply if an authority subpoenas your data. In June 2024, on the second anniversary of the Dobbs ruling, Clue repeated in a public post that Clue has never disclosed user data to any authority. Clue isn’t ad-free behind the scenes, though. The same policy says it uses Adjust to measure its own ad campaigns, which passes installs and subscriptions to networks such as Meta and TikTok.

The App Store labels sum it up. Under Data Used to Track You, Clue lists Identifiers. Flo lists Purchases, Location, Identifiers and Usage Data. Our guide to whether period tracker apps are safe shows how to read those labels for any app.

Can you share Flo or Clue with a partner?

Both let you, and they work differently. Flo for Partners gives one partner a view-only calendar and daily tips about your phase, and basic access is free. Flo says it’s built for male-female couples because the app tracks one cycle at a time.

Clue Connect sends your period days, fertile days, ovulation and PMS to people you invite, who see them on a calendar in their own Clue app. It’s for partners, friends or family. Clue’s release notes say you can now share with more than one person. Sharing needs Clue Plus, viewing is free, and it only runs one way. Neither app shows your moods or symptoms to the other person. Our partner-sharing guide compares these with Apple’s Health Sharing.

Do you need an account for Flo or Clue?

Clue requires one. It dropped account-free use in 2019 after users lost their history with their phones, and now backs everything up to its EU servers. Flo asks you to register with email, Google or Apple. Its help centre says you can skip it, but then you can’t restore your data on a new phone. If you want no account anywhere, our guide to period trackers that work without one lists the options.

Content, platforms and the rest

Flo is the bigger app for reading. It has a library of articles, videos and audio from more than 100 health experts, a chatbot that talks you through a late period, and Secret Chats. Most of that sits behind Premium. Clue’s articles come from its own science writers and clinicians, and the full set in the app needs Clue Plus. Its online encyclopedia is free to read on the web.

On devices, Flo has an Apple Watch app and Clue doesn’t, though Clue Plus can read data from one. Both run on Android. Clue has iPhone widgets for your cycle and for logging a period. Neither app is birth control. Clue’s listing says plainly that it isn’t for contraception.

Which should you pick?

• You care most about privacy. Pick Clue. It has EU storage, a public promise to keep data from authorities and the shorter tracking label. If you’d go further, our private period tracker guide covers apps that keep nothing on a server.
• You won’t pay anything. Pick Flo. Its free tier includes partner sharing and more logging. Turn on Anonymous Mode if you don’t need sync or a partner.
• Your cycles are irregular or you’re in perimenopause. Pick Clue, and expect to pay for Clue Plus to get the perimenopause mode.
• You want your partner to see your cycle. Pick Flo if it’s one partner and you won’t pay. Pick Clue if you’ll pay, want to share with several people, or aren’t in a male-female couple.
• You want to read and learn. Pick Flo Premium. It has the larger library and the chatbot.
• You wear an Apple Watch. Pick Flo for an app on your wrist. Clue only pulls watch data in.
• You’re moving from one to the other. Log your last three periods in the new app on day one. Both say that’s enough for a usable prediction.

Flo vs Stardust, Clue vs Natural Cycles

Flo vs Stardust. Stardust is the pick if you want friends to follow your cycle. It adds them by a cycle code, and its paid tier layers on horoscopes and tarot tied to your phase. Flo has far more tracking and reading. In July 2026 TechCrunch reported Mozilla research finding that Stardust sent users’ birthdate, birth control type, goals and symptoms to the analytics firm RudderStack, so read that before you choose it for privacy.

Clue vs Natural Cycles. These do different jobs. Natural Cycles is cleared by the US Food and Drug Administration as birth control. It reads your temperature through its own band or a wearable such as an Oura ring, and you pay for a subscription plus the measuring device. Clue is a tracker that says it shouldn’t be used to prevent pregnancy. If you’re trying to avoid pregnancy without hormones, Natural Cycles is the one built for it. For everything else, Clue costs less and does more.

Our side-by-side of five period trackers and the best period tracker apps by need cover Stardust, Natural Cycles and the on-device apps in more depth.

A third option if you’d rather share with friends

Flo and Clue are built around you and maybe one other person. Plum, the iPhone app we make, is built around groups of friends. You send a private invite link, and everyone who joins sees each other’s last period, next expected period and who’s on their period today. Your symptoms, mood and fertile window never leave your account. Tracking, predictions and groups are free, and Plum Premium adds insights and tips. You sign in with Apple or Google, it only runs on iPhone, and if you’re leaving Clue you can bring your history over.