Stardust app review: how Stardust compares with Lulu
Stardust is a playful period tracker built around the moon, astrology and syncing with friends and partners, with predictions for PMS, cravings and moods. Its privacy record is mixed: TechCrunch disputed its encryption claims in 2022, and Mozilla research in 2026 found symptom data shared with an analytics firm. Lulu is a warm, mood-first iPhone tracker with no account.
Stardust in brief
Stardust (stardust.app) has a fun, Gen Z personality. Its App Store listing describes a moon calendar and cycle syncing with lunar phases, daily astrology cards tuned to your moon, sun and rising sign, predictions for your period, PMS, cravings, moods and fertility, a pregnancy mode, and the ability to invite partners or close friends to stay in sync. It's free with in-app subscriptions.
What Stardust does well
- Personality. It's genuinely fun to open, which helps people keep logging.
- Social syncing. Friends and partners can follow along, which few trackers do.
- Pregnancy mode with week-by-week updates. Lulu has no pregnancy mode.
- Wearables. It can connect wearables like Apple Watch for temperature, sleep and activity data.
The privacy history
After Roe v. Wade was overturned in 2022, Stardust rose to the top of the US App Store charts on a promise of stronger encryption. TechCrunch then analyzed the app's network traffic and reported that the encryption wasn't what users had been led to believe, and that the app was sending users' phone numbers to an analytics company.
In July 2026, research by the Mozilla Foundation, reported by TechCrunch, found Stardust was the only one of six period apps tested that shared sensitive health details (birthdate, birth control type, reproductive goals and symptoms) with an analytics firm, RudderStack, tied to a unique identifier. Stardust said RudderStack is contractually prohibited from selling the data or using it for its own purposes. Its US App Store label lists Purchases, Identifiers and Usage Data under "Data Used to Track You".
Stardust vs Lulu
| Stardust | Lulu | |
|---|---|---|
| Vibe | Moon, astrology, friends | Lulu the bunny, phase colors, kindness |
| Predictions | Period, PMS, cravings, moods, fertility | Period, fertile window, ovulation day |
| Mood | Mood predictions | Shows how you usually feel each cycle day from your own check-ins, heads-up before harder days |
| Sharing | Partners and close friends | One partner; phase, plus mood forecast if you opt in, never symptoms or notes |
| Pregnancy | Pregnancy mode | No |
| Perimenopause | Not listed | Perimenopause mode |
| Doctor export | Not listed | Doctor-ready PMS chart, CSV export |
| Platforms | iPhone, Android | iPhone |
| Account and data | Account; company servers | No account; cycle data stays on your iPhone |
| Price model | Free plus subscription | 3-day free trial, then yearly Lulu Plus |
Stardust and Lulu are both cute. The difference is where the insight comes from: Stardust leans on moon phases and astrology; Lulu learns only from your own daily check-ins and your own cycles.
Who each suits
Stardust suits you if astrology and moon phases make tracking fun, you want to sync with friends, or you need pregnancy mode, and you've weighed its privacy history. Lulu suits you if you want the warmth without the zodiac: a mood forecast built from your own data, a partner heads-up that never reveals symptoms, and no account, with cycle data that stays on your iPhone.
Sharing: friends and partners
Stardust lets you invite partners or close friends to stay in sync with your period, trying to conceive or pregnancy, which suits people who like a group chat vibe. Lulu's partner sync is narrower on purpose: one partner, invited with a private iCloud link, who sees your name, cycle day, phase and next period with tips on how to help, plus today's mood, tomorrow's forecast and your fertile window only if you turn them on. Never your symptoms, notes or history, and you can stop any time. See how partner sync works.
A note on the moon
Many people love lunar tracking as a ritual, and that's fine. Research hasn't shown that menstrual cycles reliably sync with the moon for most people. Read more in does the moon affect your period? For other options, see Stardust alternatives.
Frequently asked questions
Is the Stardust app safe?
Many people use it, but its privacy record is mixed: TechCrunch disputed its 2022 encryption claims and Mozilla's 2026 research found it sharing symptom data with an analytics firm. Read its current policy before deciding.
Is Stardust free?
Stardust is free to download with optional subscriptions for premium features.
Does Lulu use astrology?
No. Lulu's mood forecast comes only from your own check-ins and cycles.
Can I share Lulu with friends like Stardust?
Lulu's partner sync shares with one partner you invite. It shows your phase and next period, plus your mood forecast if you choose, never your symptoms, notes or history.
Sources
- Stardust Period Tracker on the App Store (US)
- TechCrunch: Stardust period tracker and users' phone numbers (June 2022)
- TechCrunch: Stardust shares users' health data with analytics firm, says Mozilla research (July 2026)
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
Stardust alternatives: cute, social and private period trackersLooking for a Stardust app alternative? Compare Lulu, Clue, Flo, Apple Cycle Tracking and Euki on mood, partner sharing, privacy and price, honestly.
Period trackers that don't share your data: how to choose a private oneWant a period tracker without data sharing? How period apps handle your data, what went wrong at Flo, Maya and Stardust, and how to check any app yourself.Does the moon affect your period?Does the moon affect your period? The lunar cycle and menstrual cycle are close in length, but the evidence for a link is weak. What studies found.How Lulu partner sync works: share your cycle with your partner, privatelyHow to share your cycle with a partner in Lulu: the invite, what your partner sees, what stays private, and how to stop sharing. No Lulu server involved.
Period mood calculator: how might I feel today?Period mood calculator: find your cycle phase today and the mood people often feel in it, then learn how to build a personal forecast from your own days.