Clue vs Stardust: Which Period Tracker Fits You? (2026)
Choose Clue if privacy and a research-backed, no-frills design matter most; it is CE-marked as a Class 1 medical device in the EU. Choose Stardust if moon-phase and hormone-stage content is what keeps you tracking, and read its privacy record first. Veya, our app, suits people who want cycle, mood and lab tracking in one record.
Full Transparency
This comparison is published by Holland Neurotech Inc., the company behind Veya. We've included Veya as a third option where relevant. We've done our best to compare Clue and Stardust fairly based on each app's published features, pricing, and public record. If Clue or Stardust is the better fit for you, use it.
Quick Answer
Clue and Stardust hold close to opposite ideas of what opening a period tracker should feel like. Clue leans on documentation: a CE mark and published research partnerships, and it scored 8 out of 10 in Mozilla's July 2026 privacy review. Stardust leans on personality, with moon-phase content and a visual style you either love or don't. Veya sits outside that split, folding cycle tracking into a broader health record. Here's how the three compare:
- If science and privacy matter most: Go with Clue. Berlin-based, CE-marked as a Class 1 medical device in the EU, with published research partnerships.
- If the tracker itself needs personality to hold your attention: Go with Stardust. Moon-phase and hormone-stage content, cycle sharing with friends.
- If you want cycle, symptom, mood, and lab tracking in one free app: Try Veya.
Clue and Stardust rarely get compared directly, and that's part of why the comparison is useful. They're not chasing the same user. Clue was built in Berlin in 2012 around a clinical, research-backed approach to cycle prediction, and it became a CE-marked Class 1 medical device in the EU in 2023 (Clue). Stardust is run from New York and takes a design-forward, moon-phase, astrology-flavored approach to the same core job, tracking your cycle.
Both companies also handle your data very differently, and that difference showed up clearly in a Mozilla Foundation privacy review published in July 2026. We'll walk through what you get with each app, how their approaches to privacy actually compare, and a third option built around a different premise: tracking your whole health picture rather than just your cycle.
The Short Version
If you're in a rush, here's the quick breakdown:
| Clue | Stardust | Veya | |
|---|---|---|---|
| Best for | Science and privacy | Daily ritual, astrology feel | Whole-health tracking |
| Company base | Berlin, Germany | New York, US | US-based |
| Platform | iOS + Android | iOS + Android | iOS only (+ web app) |
| Design | Clinical, minimal | Moon-phase, astrology visuals | Simple, metric-focused |
| Premium price (annual) | ~$39.99/yr | ~$24.99–$39.99/yr | ~$49.99/yr |
| Privacy record | CE-marked, GDPR; 8/10 in Jul 2026 Mozilla review | 2/10 in a Jul 2026 Mozilla review | No ads, no data selling |
Want more detail? Keep reading.
Clue: What You Get
Clue was founded in Berlin in 2012 by Ida Tin, Hans Raffauf, Moritz von Buttlar, and Mike LaVigne, and it's built its identity around a clinical, research-driven approach to cycle tracking.[1] Its About page says the app became CE-marked as a Class 1 medical device in 2023, and its US App Store listing carries an FDA Owner/Operator number.[1][3] That page lists research with Oxford University (2018) and the Kinsey Institute (2019).[1]
Features
- Cycle tracking with predictions Clue describes as clinically validated
- 200+ symptoms and experiences, including cramps, mood, energy, skin, and sleep
- Ovulation and fertile-window predictions
- An in-app article library
- Wearable sync, including Apple Watch, Oura, WHOOP, Withings, and Fitbit (some syncing may require Clue Plus, check the app for your tier)
- Clean, gender-neutral, clinical interface
Strengths
Privacy is Clue's clearest advantage. It's based in Berlin, and its privacy policy says it meets German and EU legal requirements and that sensitive health data you track is never shared with or sold to advertisers.[2] Mozilla's July 2026 review scored Clue 8 out of 10, noting symptom data stayed in Clue's own analytics and birth control and fertility details were withheld from one third-party call.[5]
The science-first framing has documentation behind it. Clue lists research collaborations on its About page and the app is CE-marked as a medical device in the EU.[1] If you want a tracker with that kind of paper trail, Clue offers it.
The design stays out of the way. No zodiac signs, no lunar framing. Just cycle and symptom data in a minimal interface, which a lot of people specifically want after trying trackers with more personality baked in.
Limitations
Deeper features sit behind Clue Plus. The App Store listing describes Clue Plus as adding deeper analysis, advanced predictions, and personalized insights ($39.99/year or $9.99/month, as of October 2026).[3] Some wearable syncing may also require Plus, so check the app for your tier.
No nutrition, fitness, or mood-focused tracking beyond symptoms. Clue stays centered on cycle and reproductive health. If you want meal logging, workout tracking, or a dedicated mood log alongside your cycle, that's a separate app.
No astrology or lifestyle framing, which is either a strength or a limitation depending on what keeps you opening a tracker consistently.
Pricing
Free: Cycle and symptom tracking, ovulation predictions, article library.
Clue Plus: $9.99/month or $39.99/year on the US App Store, as of October 2026. Adds deeper analysis, advanced predictions, and personalized insights. Check current pricing in-app, as it varies by region.[3]
Download: Available on iOS and Android
Stardust: What You Get
Stardust is developed by Stardust App LLC, based in New York, and describes itself as and says it never sells or shares personal health information.[4] It pairs standard period tracking with moon-phase visuals, zodiac-flavored "witch type" content, and a distinct look that's made it one of the more design-forward period apps around, with a 4.8 out of 5 rating from roughly 119,000 App Store ratings as of September 2026.[4]
Features
- Cycle, ovulation, and hormone-stage tracking with a daily readout of what a given phase can feel like
- A moon-phase wheel that lines up lunar phases with your cycle, plus zodiac and "witch type" content
- Pregnancy tracking, including a 3D and AR baby visualization feature[4]
- Symptom logging covering flow, cervical mucus, feelings, cravings, and cycle disruptors
- Wearable data from Apple Watch and Oura Ring[4]
- Friend and partner sharing for comparing cycles
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 tracking feel less like a chore, and that's a real reason people keep using a tracker instead of abandoning it after a week.
The core experience is free. Cycle tracking, symptom logging, and the daily content are available without paying, with Stardust Plus as an optional add-on.
The feature set has grown. Pregnancy tracking and wearable sync with Apple Watch and Oura Ring are both listed as current features, which is more than some lighter astrology-flavored trackers offer.[4]
Limitations
Its privacy record is the biggest thing to weigh. Mozilla's Nothing Personal review, published July 16, 2026, gave Stardust 2 out of 10, the lowest of the six period apps tested. It reported data going to third-party tracking services from the moment the app opened, and birth control type, reproductive goals, birthdate and logged symptoms reaching analytics and data-pipeline tools, including RudderStack.[5] Stardust told Mozilla RudderStack receives nothing that identifies the user, and its App Store description says "We never sell or share your personal health information," so read the current policy yourself.[4][5]
Its privacy policy has kept changing. The same Mozilla review found the policy had been revised twice in about seven months, with the version live as of May 2026 naming Meta's and Google's ad-measurement tools as data partners.[5]
Limited control over sharing. Mozilla's testers found no clear in-app setting that fully disables the early third-party data transmission.[5] If any of this rules Stardust out, our Stardust alternatives roundup covers six other trackers.
Pricing
Free: Core cycle and symptom tracking, moon-phase and hormone content.
Stardust Plus: roughly $6.99/month, or $24.99 to $39.99 a year depending on the offer, as of September 2026. Shorter All Access plans run $2.99 to $4.99. Check current pricing in-app.[7]
Download: Available on iOS and Android
The Third Option: Veya
Clue and Stardust both approach the same job, tracking your period, from different angles: clinical science on one side, daily ritual and design on the other. Neither one tracks mood, sleep, nutrition, or lab results alongside your cycle in real depth. That's the gap Veya is built to fill: instead of being a cycle tracker with a few extras, it tracks your whole health picture, cycle included, in one place.
Where It Adds Scope
- Cycle tracking with automatic phase detection and fertility predictions
- Whole-health logging: 350+ metrics across mood, sleep, fitness, and nutrition tracked alongside your cycle
- Support for uploading lab results so they sit next to your cycle and symptom history
- 1-click logging for fast daily tracking
- Correlation insights showing how your lifestyle connects to your cycle
- No ads, no data selling
Honest Limitations
- No CE mark or clinical research partnerships like Clue's, and no moon-phase or astrology content like Stardust's.
- iOS only. There's no Android app. A web app covers other platforms, but the full experience is iPhone-only right now.
- Smaller, newer app. It doesn't have Clue's track record since 2012 or Stardust's user base.
- 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 | Clue | Stardust | Veya |
|---|---|---|---|
| Cycle tracking | ✅ | ✅ | ✅ |
| Pregnancy mode | ✅ Listed as a mode | ✅ | ✅ |
| Symptom tracking | ✅ 200+ symptoms | ⚠️ Lighter | ✅ Detailed |
| Mood / whole-health logging | ❌ | ⚠️ Basic | ✅ Mood, sleep, fitness, nutrition |
| Lab result uploads | ❌ | ❌ | ✅ |
| Moon-phase / astrology content | ❌ | ✅ Core feature | ❌ |
| Wearable integration | ⚠️ Apple Watch, Oura, WHOOP, more | ⚠️ Apple Watch, Oura | ✅ Apple Watch, Oura, Garmin |
| Medical device / regulatory status | ✅ CE-marked (EU), Class 1 | ❌ | ❌ |
| Content library | ✅ Article library | ⚠️ Daily readouts, lighter depth | ⚠️ Limited |
| Privacy practices | ✅ GDPR; 8/10 Mozilla review, Jul 2026 | ⚠️ 2/10 Mozilla review, Jul 2026 | ✅ No ads, no data selling |
| Free tier quality | ⚠️ Basic, with upsell prompts | ✅ Usable core tracking | ✅ Generous, no ads |
| Price (annual) | ~$39.99/yr | ~$24.99–$39.99/yr | ~$49.99/yr |
Should You Choose Clue, Stardust, or Veya?
Neither app is the right answer for everyone. What decides it is which one you'll still be opening in three months, and how heavily Stardust's privacy record weighs on you. Here's the honest breakdown:
Choose Clue if:
- Privacy and a documented, research-backed approach matter most to you
- You want a CE-marked app
- You prefer a clinical, no-frills design without lifestyle framing
- You're comfortable with a focused cycle tracker (no mood, nutrition, or lab tracking built in)
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
- You've read the current privacy policy and are comfortable with what it discloses
Choose Veya if:
- You want cycle tracking folded into whole-health logging, symptoms, mood, and lab results
- You want to see how your lifestyle habits connect to your cycle
- You want a generous free tier with no ads
- Astrology framing and clinical certifications aren't why you open a tracker
If your cycles are unpredictable and neither app's calendar-based forecast is working for you, our guide to period trackers for irregular cycles looks at what actually helps there. And if you want Flo added to the mix, Flo vs Clue vs Stardust covers all three together.
How Do Clue and Stardust Handle Your Privacy Differently?
Cycle and symptom data is sensitive, and Clue and Stardust represent genuinely different approaches to handling it, not just different marketing language. Here's the factual record for each, with dates.
Clue: Berlin, GDPR, and a CE Mark
Clue is based in Berlin, Germany, and its privacy policy says its data handling meets German and EU legal requirements and that sensitive health data is never shared with or sold to advertisers.[2] (The same policy says some non-health app events go to advertising networks.) Its About page says the app became a CE-marked Class 1 medical device in the EU in 2023, a regulatory status tied to how its cycle and ovulation-prediction features are documented, not a claim that it functions as birth control. Clue's App Store listing says it should not be used as a contraceptive.[1][3] Mozilla scored Clue 8 out of 10 in July 2026.[5]
Stardust: A Low Score From an Independent Review
Stardust's App Store description says it never sells or shares personal health information.[4] A Mozilla Foundation review published in July 2026, part of its Nothing Personal series testing period trackers, reported a different picture: Stardust sent data to third-party tracking services from the moment the app opened, before a user entered anything, and birthdate, birth control type, reproductive goals and specific symptoms reached analytics and data-pipeline tools.[5] Per the same coverage, RudderStack received a logged symptom with a timestamp and persistent user ID, and Stardust said it does not give RudderStack any information that can identify the user.[5] Mozilla scored Stardust 2 out of 10, the lowest of the six period apps it tested.[5]
The same review found Stardust's privacy policy had been revised twice in roughly seven months, with the version live as of May 2026 naming Meta's and Google's ad-measurement tools as recipients of activity data.[5] This is not unique to Stardust: Mozilla also flagged Flo (7 out of 10) for an identifier sent to AppsFlyer on first launch. Read Stardust's current privacy policy directly if this is a deciding factor for you.
Veya: Privacy-Focused, Smaller Scale
Veya doesn't run ads and doesn't sell user data. That said, it's a newer, smaller company without the years of independent privacy review that Clue or Stardust have been through, and it doesn't carry Clue's CE mark. The no-ads, no-data-selling approach is a meaningful commitment, but it hasn't faced the same level of outside scrutiny yet.
Frequently Asked Questions
Is Clue or Stardust more accurate for period predictions?
Both apps use algorithm-based prediction that improves with more logged history, and neither publishes independent accuracy figures against outside data. Clue describes its predictions as built on published cycle research and clinically validated modeling. Stardust layers moon-phase and hormone-stage content on top of its own cycle predictions, but the core method is the same calendar and symptom-based approach most trackers use. For irregular cycles, expect either app's forecast to be less reliable, and lean on the patterns you log rather than the prediction itself.
Which is better for privacy, Clue or Stardust?
Clue has the stronger public privacy record. It's based in Berlin under EU GDPR law, and its privacy policy says sensitive health data is never shared with or sold to advertisers; Mozilla scored it 8 out of 10 in July 2026. Stardust, based in New York, states it never sells or shares personal health information, but a Mozilla Foundation review published in July 2026 scored Stardust 2 out of 10, the lowest of six, after finding sensitive details (including birth control type and specific symptoms) reached analytics and data-pipeline tools, and that its privacy policy had been revised twice in about seven months, disclosing more ad-partner data sharing including Meta's and Google's ad-measurement tools as of May 2026. Read each company's current privacy policy yourself before logging sensitive symptoms.
Is Clue a medical device?
Clue's About page says it became a CE-marked Class 1 medical device in the EU in 2023, and its US App Store listing lists an FDA Owner/Operator Number. That regulatory status covers how its cycle-tracking and prediction features are built and documented, not a claim that the general tracking app functions as contraception. Clue's App Store listing says it should not be used as a contraceptive.
What happened with Stardust's privacy policy in 2026?
A Mozilla Foundation review published in July 2026, part of its Nothing Personal series on period trackers, gave Stardust a score of 2 out of 10, the lowest of the six apps it tested. The review found Stardust sent data to third-party tracking services before users had entered any information, and separately shared health details like birthdate, birth control type, reproductive goals, and specific symptoms with analytics and data-pipeline tools such as RudderStack. It also found the app's privacy policy had been revised twice in roughly seven months, with the most recent version (as of May 2026) naming Meta's and Google's ad-measurement tools as data partners. Stardust's public marketing states it never sells or shares personal health information, so read its current policy directly if this affects your decision.
What's a good alternative to Clue and Stardust?
If the reason you're comparing is that neither app tracks anything outside your cycle, Veya covers different ground: mood, sleep, fitness, nutrition, and uploaded lab results sit in the same record as your cycle, with correlation insights across them. Core features are free with no ads. It's iOS only (a web app covers other platforms), it carries neither Clue's research partnerships nor Stardust's daily content, and it's newer and smaller than both.
References
- Clue (Biowink GmbH). About Clue. helloclue.com/about-clue. Fetched October 9, 2026.
- Clue (Biowink GmbH). Privacy Policy. helloclue.com/privacy. Fetched October 9, 2026.
- Clue. App Store listing. apps.apple.com/us/app/clue-period-cycle-tracker. Fetched October 9, 2026.
- Stardust (Stardust App LLC). App Store listing. apps.apple.com (Stardust Period Tracker, id1495829322). Fetched October 9, 2026.
- Mozilla Foundation, Nothing Personal. Hands-on privacy testing of six period tracking apps by Shoshana Wodinsky, published July 16, 2026, scoring Stardust 2 out of 10. mozillafoundation.org/en/nothing-personal. The Mozilla page itself returned an access error on October 9, 2026, so the findings here are as summarized in PPC Land, "Mozilla rates Stardust 2 of 10 over symptom data sent to third parties," ppc.land. Fetched October 9, 2026.
- Stardust (Stardust App LLC). In-app purchase tiers listed on the App Store. apps.apple.com (Stardust Period Tracker, id1495829322). Fetched October 9, 2026.
Facts checked against official pages and independent reporting, October 2026. Prices and policies change, so confirm current details on each company's site before subscribing or logging sensitive data.
Want to See More Apps Compared?
This guide focused on Clue vs Stardust, but there's more to look at depending on why you're comparing. If Flo is also in the mix, or you want the science-vs-privacy angle taken further, these go deeper.
- Clue vs Flo: Which Period Tracker Is Actually Better? →
- Flo vs Stardust: Which Period Tracker Fits You? →
- Flo vs Clue vs Stardust: 2026 Period App Showdown →
Related Articles
- Best Period Tracker App 2026: Clue vs Flo vs Ovia (6 Apps Compared)
- Best Period Tracker for Irregular Cycles
Other App Comparisons
- Clue vs Natural Cycles: Which One Should You Use?
- Stardust Alternatives 2026: 6 Period Trackers Compared
- Flo vs Veya: Which One Should You Use?
- Best Symptom Tracker App for Women 2026: 5 Apps Compared
Try Veya Free
Cycle, symptom, mood, sleep, fitness, and nutrition tracking in one app. No ads. 1-click logging.