Your cycle, your data, your way
Free cycle tracking with AI insights, partner sharing, and gamification โ built for everyone, not just women.
AI Smart Logging
Describe your day in natural language and let AI fill in the details. No more tapping through endless menus.
- Natural language input โ just type how you feel
- AI parses symptoms, mood, and temperature
- Review and confirm in one tap
Partner Sharing
Share a filtered view of your cycle with your partner. They see what you choose to show โ nothing more.
- Choose exactly what to share
- Real-time cycle status sync
- Works for any kind of partnership
Privacy First
AES-256 encryption, GDPR compliant, full data export. Your data belongs to you โ always.
- AES-256-GCM encryption at rest
- Full GDPR compliance with data export
- Delete everything with one tap
Healthy Habits
Daily quests, XP, streaks, and a pixel avatar you can customize. Healthy habits, made fun.
- Daily quests and streak rewards
- Level up with XP and unlock badges
- Customize your pixel avatar
Goal-Dependent UI
Whether you're tracking for contraception, pregnancy, or general health โ the entire app adapts to your goal.
- UI adapts to your tracking goal
- Relevant insights per goal type
- Switch goals anytime โ the app follows
Smart Predictions
AI analyzes your patterns to predict your next period, fertile window, and PMS symptoms with increasing accuracy over time.
- Period predictions improve each cycle
- Fertile window estimation
- PMS symptom forecasting
Medication Tracking
Track medications and get pill reminders. Never miss a dose.
- Set reminders for any medication
- Log doses and track adherence
- See how medications affect your cycle
Biometric Lock
Secure your app with Face ID or Touch ID.
- Face ID and Touch ID support
- Auto-locks when you leave the app
- No passcode stored on any server
Your data. Your rules.
Typical tracking apps
What Cythr sees
No paywall. No ads. No data selling. Ever.
Cythr is funded by optional supporter donations. Every feature is free for everyone โ forever. Supporters get cosmetic perks like themes, badges, and priority AI, but never exclusive functionality.
| Feature | Cythr | Flo | Clue | Natural Cycles | Stardust | Period Calendar |
|---|---|---|---|---|---|---|
| Price | Free | Free / $49.99/yr | Free / $39.99/yr | $149.99/yr | Free / $24.99/yr | Free + ads |
| AI Features | LLM-powered | Rule-based | None | None | None | None |
| Partner Tracking | Built-in | Limited | No | No | No | No |
| Privacy | AES-256 encrypted | Legal issues | GDPR | Good | Undisclosed trackers | Ads + trackers |
| Healthy Habits | XP, streaks, badges | No | No | No | Basic | No |
| Languages | Multilingual | 22+ | 15+ | 8+ | English only | 20+ |
Supporter perks
Articles
Evidence-based articles on cycle health, fertility, and wellness
ENTJ Friendships: How the Commander Builds an Inner Council
Understand how ENTJs approach friendship with strategic clarity โ selecting high-caliber people and investing fiercely in mutual growth.
Read more →ENFJ Friendships: How the Protagonist Uplifts Everyone
Learn how ENFJs create friendships that feel like being championed โ seeing your potential before you do.
Read more →ESFJ Friendships: How the Consul Creates Community
Discover how ESFJs build the richest social networks โ natural community-builders who make everyone feel they belong.
Read more →ESTJ Friendships: How the Executive Leads Even in Social Life
Explore how ESTJs approach friendship with decisive energy โ organizing, showing up, and expecting the same in return.
Read more →ENTP Friendships: How the Debater Keeps Everyone on Their Toes
Learn how ENTPs approach friendship as intellectual sport โ arguing for fun and somehow becoming your most stimulating companion.
Read more →ENFP Friendships: How the Campaigner Collects and Loses Connections
Discover how ENFPs befriend the entire world yet struggle to maintain depth โ 500 friends but sometimes truly known by none.
Read more →Built by someone who cared enough to make it free
Every period tracker on the market either charges you $60/year for basic features, sells your most intimate data, or both. Cythr exists because that's unacceptable. Built as a solo project with obsessive attention to detail โ from AES-256 encryption to AI-powered logging to full multilingual support including RTL. This isn't a startup chasing growth metrics. It's a tool built for the people who use it.
Share Cythr, get rewarded
Invite a friend and you both get 14 days of Supporter for free.
Sign up and find your referral code in the app
Share it with a friend who downloads Cythr
They enter your code โ both of you get Supporter
days of Supporter for both of you โ free
Join 1,200 people tracking smarter
Free. Private. AI-powered.
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Trusted worldwide
“I switched from Flo after the data scandal. Cythr gives me the same features without selling my most intimate data. It's refreshing to use an app that actually respects privacy.”
“The AI Smart Log changed everything. I just type how I feel and it logs everything automatically. No more tapping through 20 different symptom buttons.”
“The partner sharing feature is amazing. My partner can see when I'm having a tough day without me having to explain. It brought us closer.”
“Finally an app in Hebrew that actually works well! The RTL support is perfect and the translations feel natural, not machine-generated.”
“The streaks and XP system makes me actually want to log every day. It turned tracking into a healthy habit. My prediction accuracy went from 60% to 90% in two months.”
“I was paying $60/year for Flo. Cythr does more, for free. The AI features alone would be worth a premium, but they give it away. Respect.”