Flo vs Stardust: Which Period Tracker Fits You? (2026)
Flo and Stardust are the two apps Gen Z period-tracker conversations keep coming back to, and they're built around almost opposite ideas. Flo is the feature-deep, community-heavy option with roughly 77 million active users. Stardust is the moon-phase, astrology-flavored option people describe as fun to open. This guide covers what you actually get with each, both apps' privacy records laid out factually, and a third option you might not have considered.
Full Transparency
This comparison is published by Holland Neurotech Inc., the company behind Go Go Gaia. We've included Go Go Gaia as a third option where relevant. We've done our best to compare Flo and Stardust fairly based on each app's published features, pricing, and public record. If Flo or Stardust is the better fit for you, use it.
Quick Answer
Flo and Stardust are aimed at different reasons for opening a tracker. Flo is best if you want the deepest feature set and the largest community, roughly 77 million active users and thousands of medically reviewed articles. Stardust is best if you want cycle tracking that feels more like a daily ritual, with moon-phase content and a distinct visual style that's made it popular on TikTok. And if you want cycle tracking folded into a broader health picture, Go Go Gaia is worth a look. Here's how they compare:
- If you want the deepest feature set and biggest community: Go with Flo. ~77M active users, an AI health assistant, and a large content library.
- If you want a tracker that feels fun to open every day: Go with Stardust. Moon-phase and hormone-stage content, cycle sharing with friends.
- If you want cycle, mood, sleep, and nutrition tracking in one free app: Try Go Go Gaia.
Flo and Stardust are two of the most-discussed period trackers right now, and the comparison isn't really "which one is better." It's closer to "which one is built for the reason you open a period tracker in the first place." Flo is the polished, feature-complete option with the largest community in the category. Stardust is the smaller, design-forward option that leans into moon phases and daily hormone explanations, and it's become one of the apps Gen Z talks about most on TikTok.
Both apps also have documented privacy histories worth knowing before you hand over cycle data, and both have made real changes since the incidents that put them in the news. We'll walk through what you get with each, lay out the privacy record for both plainly, and cover a third option built around a different premise entirely.
The Short Version
If you're in a rush, here's the quick breakdown:
| Flo | Stardust | Go Go Gaia | |
|---|---|---|---|
| Best for | Feature depth and community | Daily ritual, astrology/lifestyle feel | All-in-one health tracking |
| Platform | iOS + Android | iOS + Android | iOS only (+ web app) |
| Active users | ~77 million | 5M+ downloads | Smaller, newer app |
| Free tier | Usable, with ads | Usable core tracking | Most features, no ads |
| Premium price | ~$59.99/year | ~$24.99/year | ~$49.99/year |
| Privacy | FTC/class action + 2025 verdict history | 2022 criticism, since revised twice | Strong, no ads |
Want more detail? Keep reading.
Flo: What You Get
Flo is the most-used period tracker in the category, with around 77 million active users and over 300 million registered accounts. It's the app most of your friends probably already have, and that scale shows up in the feature list.
Features
- Cycle tracking with AI-powered predictions
- AI Health Assistant that checks in on symptoms like cramps, fatigue, and mood
- Thousands of health articles reviewed by 100+ medical professionals
- Secret Chats: anonymous community discussions, with about 7 million people chatting monthly
- Pregnancy mode with week-by-week tracking, included free
- Apple Health integration and an Apple Watch companion app
- Partner sharing for joint tracking
Strengths
The community is the largest in the category. Secret Chats put you in anonymous discussions with millions of other users, and roughly 7 million people participate monthly across topics from PCOS to perimenopause. If you have a question about a symptom at 2am, someone in that community has probably already asked it.
The content library is extensive. Thousands of articles cover cycle, fertility, and general health topics, reviewed by medical professionals. If you want to learn while you track, very few trackers offer more.
Free pregnancy mode. Flo includes pregnancy tracking in its free tier, with week-by-week updates and educational content, no subscription required.
Limitations
Privacy is the big concern. Flo settled with the FTC in 2021 for sharing period and pregnancy data with Facebook and Google without user consent. A related class action against Flo, Google, and Flurry has preliminary court approval for a combined $59.5 million settlement, with a final approval hearing set for October 2026, and a jury separately found Meta liable in August 2025 for its role in receiving that data. Flo has since added Anonymous Mode and open-sourced it.
Ads and paywalls. Free users see ads, and the AI Health Assistant, ad-free experience, and full content library sit behind Flo Premium (~$59.99/year as of 2026).
No nutrition, habit, or sleep tracking. Flo stays focused on cycle and pregnancy tracking. You won't find meal logging or habit tracking inside the app.
Pricing
Free: Cycle and symptom tracking, pregnancy mode, community access. Includes ads.
Flo Premium: ~$12.99/month or ~$59.99/year as of 2026. Adds the AI Health Assistant, an ad-free experience, and full content library access. Check current pricing in-app, as it can shift with promotions.
Download: Available on iOS and Android
Stardust: What You Get
Stardust pairs standard period tracking with moon phases, hormone-stage explanations, and a distinct visual style that's made it one of the more-discussed period apps on TikTok. It has more than 5 million downloads and a 4.76 out of 5 rating across roughly 110,000 App Store ratings.
Features
- Cycle tracking with a daily readout of where you are hormonally and what that can feel like
- Cycle syncing content that aligns your cycle with lunar phases, plus a moon calendar
- "Cycle Horoscope" and zodiac-matched content
- Cycle Recap, added in 2026, summarizing your last cycle's sleep and activity patterns by phase
- Friend syncing so you can compare cycles with people you share the app with
- Standard symptom, mood, and period-length logging
Strengths
It's genuinely fun to open. Stardust is one of the few trackers people describe that way. The daily hormone narrative and moon-phase framing make cycle education more approachable than a plain calendar view, and that's a real reason people stick with a tracker instead of abandoning it after a week.
The core experience is free. Cycle tracking, symptom logging, and the daily content are all available without paying, with an optional paid tier for deeper features.
It's improved its privacy posture since 2022. After reporting found Stardust marketed itself as encrypted without using true end-to-end encryption, and after its privacy policy included language about cooperating with law enforcement whether or not legally required, the company walked both back: it removed the overstated encryption claim and dropped the law-enforcement language. Stardust says it has never actually received a law enforcement request for user data. That's a real, credit-worthy change from where the app stood in 2022.
Limitations
The 2022 criticism is worth knowing. Reporting that year found Stardust had shared users' phone numbers with a third-party analytics service, alongside the encryption and law-enforcement-language issues above. The company updated its practices and policy afterward.
More recent privacy scrutiny exists too. A Mozilla Foundation review published in July 2026 found that Stardust's privacy policy had been revised twice in about seven months, each revision disclosing more device and advertising data sharing, including naming Meta's and Google's ad-measurement tools as data partners as of May 2026. Its separate Health Data Privacy Policy, unchanged since October 2025, still states health data sits under a randomized ID separated from your name or contact information. Read Stardust's current privacy policy yourself before logging sensitive symptoms.
Symptom tracking is lighter than Flo's or Clue's, and there's no pregnancy mode. Stardust also requires an account, with no local-only option for people who want data to stay entirely on-device. If any of that rules Stardust out for you, our Stardust alternatives roundup looks at six other trackers.
Pricing
Free: Core cycle and symptom tracking, moon-phase and hormone content.
Stardust Plus: ~$2.99/week, ~$3.99/month, or ~$24.99/year as of 2026. Adds deeper insights, unlimited friend syncs, and additional content. Check current pricing in-app.
Download: Available on iOS and Android
The Third Option: Go Go Gaia
If neither Flo's depth-and-community approach nor Stardust's daily-ritual approach is quite what you're after, and what you actually want is your cycle tracked alongside the rest of your health, that's where Go Go Gaia fits in. It's a newer app built around one idea: instead of being a cycle tracker with a few extras, it tracks your whole health picture, cycle included, in one place.
What It Adds
- Cycle tracking with automatic phase detection and fertility predictions
- Mood, sleep, fitness, and nutrition tracking built in, 350+ metrics total
- 1-click logging for fast daily tracking
- Correlation insights showing how your lifestyle connects to your cycle
- Available on iOS and as a web app
- No ads, no data selling
Honest Limitations
- No community and no moon-phase content. Go Go Gaia doesn't try to be either Flo's discussion forums or Stardust's daily astrology narrative. It's focused on your own data.
- iOS only. There's no Android app. A web app is available for other platforms, but the full experience is iPhone-only right now.
- Smaller, newer app. It doesn't have Flo's 77 million active users or Stardust's TikTok-driven following. Fewer reviews, a shorter track record.
- AI features are premium. Advanced insights require a subscription (~$9.99/month or ~$49.99/year).
Pricing
Free: Cycle, mood, sleep, fitness, and nutrition tracking. No ads.
Premium: ~$9.99/month or ~$49.99/year for AI features and advanced insights.
Download: Available on iOS App Store
Side-by-Side Feature Comparison
Here's every major feature compared across all three apps. Check marks mean the feature is included, locks mean it requires a paid subscription, warning signs mean it's limited, and X marks mean it's not available.
| Feature | Flo | Stardust | Go Go Gaia |
|---|---|---|---|
| Cycle tracking | ✅ | ✅ | ✅ |
| Pregnancy mode | ✅ Free | ❌ | ✅ |
| Mood / symptom tracking | ✅ Deep | ⚠️ Lighter | ✅ Detailed |
| Moon-phase / astrology content | ❌ | ✅ Core feature | ❌ |
| AI assistant | 🔒 Paid | ❌ | 🔒 Paid |
| Community | ✅ ~77M users | ⚠️ Friend syncing only | ❌ |
| Sleep / activity tracking | ❌ | ⚠️ Cycle Recap only | ✅ Full logging |
| Nutrition tracking | ❌ | ❌ | ✅ |
| Content library | ✅ Thousands of articles | ⚠️ Daily readouts, lighter depth | ⚠️ Limited |
| Privacy practices | ⚠️ FTC/class action + 2025 verdict | ⚠️ 2022 issues, since revised | ✅ No ads, no data selling |
| Free tier quality | ⚠️ Usable, with ads | ✅ Usable core tracking | ✅ Generous, no ads |
| Price (annual) | ~$59.99/yr | ~$24.99/yr | ~$49.99/yr |
Which Should You Choose?
There's no single "best" app here. It comes down to what actually gets you to open a tracker consistently. Here's the honest breakdown:
Choose Flo if:
- You want the deepest feature set and the largest community of people tracking cycles
- Health education and medically reviewed articles matter to you
- You want a free pregnancy mode
- You need Android support
- You're comfortable with Flo's privacy history (or willing to use Anonymous Mode)
Choose Stardust if:
- You stopped opening other trackers because they felt like a chore
- You like moon-phase and daily hormone content more than a plain symptom log
- You want to sync cycles with friends inside the app
- Detailed symptom logging isn't your main priority
- You've read the current privacy policy and are comfortable with it
Choose Go Go Gaia if:
- You want cycle, mood, sleep, fitness, and nutrition tracking in one app
- You want to see how your lifestyle habits connect to your cycle
- You want a generous free tier with no ads
- You're on iOS (or okay using the web app on other platforms)
- Community and daily content aren't why you open a tracker
Privacy: What Each App's Record Actually Shows
Period data is sensitive, and both apps have a documented history worth reading before you commit. Here's the factual record for each, with dates.
Flo: FTC Settlement, Then a 2025 Verdict
In 2021, the FTC settled with Flo over sharing users' health data with companies including Facebook and Google without proper consent. A related class action against Flo, Google, and Flurry has preliminary court approval for a combined $59.5 million settlement, with a final approval hearing set for October 2026, and a jury separately found Meta liable in August 2025 for its role in receiving that data.
Flo has since added Anonymous Mode, which separates your health data from your identity, and open-sourced it. These are real changes, made after years of public scrutiny. Whether that history changes your decision is a personal call.
Stardust: 2022 Criticism, Since Revised, With New Scrutiny in 2026
In 2022, reporting found that Stardust had shared users' phone numbers with a third-party analytics service, and that the app had marketed itself as "encrypted" using language that implied end-to-end encryption when its actual encryption was standard, not end-to-end. Its privacy policy at the time also stated it would comply with law enforcement requests for user data whether or not legally required to, a detail that drew attention after Roe v. Wade was overturned that year.
Stardust has since made real changes: it removed the overstated encryption claim and dropped the "whether or not legally required" language about law enforcement cooperation. The company says it has never actually received a law enforcement request for user data.
More recently, a Mozilla Foundation review published in July 2026 found that Stardust's privacy policy had been revised twice in roughly seven months, with each revision disclosing more device and advertising data sharing, including naming Meta's and Google's ad-measurement tools as data partners as of May 2026. Its separate Health Data Privacy Policy, unchanged since October 2025, still states that health data itself sits under a randomized ID, separated from your name or contact information. Read the current version of both policies yourself if this is a deciding factor for you.
Go Go Gaia: Privacy-Focused, Smaller Scale
Go Go Gaia doesn't run ads and doesn't sell user data. That said, it's a newer, smaller company without the years of public scrutiny that Flo or Stardust have been through, and there's no GDPR certification since it's a US-based company. The no-ads, no-data-selling approach is a meaningful commitment, but it hasn't been tested by the same level of outside review.
Frequently Asked Questions
Is Flo or Stardust more accurate for period predictions?
Both use calendar-based prediction models that improve with more logged history, and neither publishes independent accuracy data. Flo has more logged cycles behind its algorithm given its larger user base. Stardust layers moon-phase and hormone-stage content on top of its own predictions, but the underlying prediction method is calendar-based like most trackers. For irregular cycles, expect either app's predictions to be less reliable, and focus on the patterns you log rather than trusting the forecast.
Which is better for privacy, Flo or Stardust?
Both have documented privacy issues worth knowing. Flo settled with the FTC in 2021 over sharing health data with Facebook and Google. A related class action against Flo, Google, and Flurry has preliminary court approval for a combined $59.5 million settlement, with a final approval hearing set for October 2026, and a jury separately found Meta liable in August 2025. Flo has since added Anonymous Mode. Stardust drew criticism in 2022 for sharing phone numbers with a third-party analytics service and for marketing itself as encrypted when it wasn't using true end-to-end encryption. It has since removed that claim and dropped language about cooperating with law enforcement whether or not legally required. A Mozilla Foundation review in July 2026 found Stardust's privacy policy had been revised twice in seven months, disclosing more ad-partner data sharing, including with Meta's and Google's ad-measurement tools as of May 2026. Neither app is a clean slate, so check each one's current privacy policy yourself.
Does Stardust still share data with law enforcement?
Stardust says it has never actually received a law enforcement request for user data. Its privacy policy previously stated it would comply with such requests whether or not legally required to, a detail that drew criticism after Roe v. Wade was overturned. The company later removed that language. Its separate Health Data Privacy Policy states health data sits under a randomized ID, separated from your name or contact information.
Is Stardust actually end-to-end encrypted?
Stardust once marketed itself as an encrypted, privacy-safe app, but reporting found it used standard encryption rather than true end-to-end encryption, and the company quietly removed that specific claim. Its current privacy materials focus on the randomized-ID approach to health data rather than an end-to-end encryption claim.
What's a good alternative to Flo and Stardust?
Go Go Gaia is worth a look if you want cycle tracking alongside mood, sleep, fitness, and nutrition in one app, with correlation insights showing how your lifestyle connects to your cycle. Core features are free with no ads. The main tradeoffs are that it's iOS only (a web app covers other platforms) and has a much smaller community than Flo or Stardust.
Is Stardust just astrology, or does it track real symptoms?
Stardust does log real symptoms alongside its moon-phase and hormone-stage content. You can track period length, mood, cravings, and other symptoms the way you would in any period tracker. The astrology and lunar framing sits on top of that logging as a daily readout, not in place of it. That said, its symptom category list is lighter than Flo's or Clue's, so if detailed symptom logging is your main goal, that's worth weighing.
How much does Flo or Stardust premium cost?
As of 2026, Flo Premium runs about $12.99/month or roughly $59.99/year. Stardust Plus runs about $2.99/week, $3.99/month, or roughly $24.99/year. Both apps have usable free tiers, and pricing can shift or vary by promotion, so check the current price inside each app before subscribing.
Want to See More Apps Compared?
This guide focused on Flo vs Stardust, but there's more to look at depending on why you're comparing. If you're weighing whether to leave Flo entirely, or want the deeper science-vs-privacy angle, these go further.
- Flo Alternatives 2026: 7 Period Trackers Compared →
- How Accurate Are Period Tracker Apps, Really? →
- Flo vs Clue vs Stardust: 2026 Period App Showdown →
Related Articles
- Period Tracking Guide: How to Track Your Cycle and Why It Matters
- Best Period Tracker App 2026: Clue vs Flo vs Ovia (6 Apps Compared)
Other App Comparisons
- Flo vs Natural Cycles: Which One Should You Use?
- Clue vs Natural Cycles: Which One Should You Use?
- Flo vs Ovia: Cycle & Pregnancy Compared (2026)
- Best Period Tracker App 2026: 6 Apps Compared
- Best Cycle Syncing Apps 2026: 28 vs Stardust vs MyFlo vs Flo
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