# 28 FAQ: Cycle Syncing, Privacy, Fertility and Gaia

Last reviewed: November 10, 2026.

Straight answers to the questions women ask before choosing a cycle app: what cycle syncing is, what 28 does with your data, what it can and can't do, and what's free.

HTML version: [FAQ](https://28.co/faq).

Comparing apps? See [the best cycle syncing apps](https://28.co/best-cycle-syncing-apps) and [Flo alternatives](https://28.co/flo-alternatives). Still stuck? Email support@28.co.

## Cycle syncing

**What is cycle syncing?** Cycle syncing means adjusting how you train, eat and rest to the four phases of your menstrual cycle: menstrual, follicular, ovulatory and luteal. Research is still mixed, so it works best when you follow how you actually feel.

**What's the best cycle syncing app?** It depends on what you want synced. For daily workouts and meals built around your phase, 28. For the original Cycle Syncing method, MyFLO. For period tracking only, Clue or Flo.

**Does cycle syncing work with irregular cycles?** It works best when the app adapts to your logged cycle rather than assuming 28 days. 28 updates your phase from what you log, and can use Oura or Apple Watch temperature.

[Compare cycle syncing apps](https://28.co/best-cycle-syncing-apps).

## Privacy

**Does 28 sell my data?** No. There are no ads in 28, and we don't sell your data.

**Is my data shared with advertisers?** No. 28 does not use your health data for advertising.

**How do I delete my data?** You can delete your account and its data at any time in the app under Profile, or email support@28.co.

[Read the privacy FAQ](https://28.co/privacy-faq).

## Fertility

**Does 28 show my fertile window?** Yes. 28 estimates your fertile window and ovulation for general awareness. Oura Ring or Apple Watch temperature can refine the estimate.

**Can I use 28 as birth control?** No. 28 is a wellness app, not a medical device or contraceptive. Fertile window estimates should not be used to prevent pregnancy.

**Can I use 28 on hormonal birth control?** 28's phase-based workouts and food are built around a natural cycle. Combined hormonal birth control usually stops ovulation, so that guidance doesn't apply in the same way. Logging symptoms, sleep and energy can still show your own patterns. Please don't stop birth control to use an app; talk to your clinician.

## Gaia, the AI companion

**What is Gaia?** Gaia is 28's AI wellness companion. Ask about your cycle, energy, cravings, workouts and food, by voice or text.

**Is Gaia medical advice?** No. Gaia gives general wellness information, not medical advice. For symptoms that worry you, see a clinician.

## Plans

**Is 28 free?** 28 is free to download, with period and cycle tracking included. Full workout and meal plans need a paid plan.