Privacy policy

Effective October 13, 2026.

Know your Limits (“the app”) is an iPhone app that computes recovery, strain, sleep and health metrics from your Fitbit Air data. It is designed so that your data stays on your phone.

Data the app uses

• Google Health data (read-only). With your permission, the app reads from the Google Health API your health metrics and measurements (heart rate, HRV, SpO₂, respiration, temperature, VO₂max), sleep, activity and workouts, and profile (sex, age). It never writes, modifies or deletes data in your Google account.
• Data you enter. Age, sex, height, weight, journal entries and migraine logs.
• Approximate location (optional). Used to estimate migraine risk from air-pressure changes.

Where data is stored and processed

Everything is processed and stored only on your iPhone. Know your Limits has no servers and never receives, stores or sees your data. Google credentials are kept in the iOS Keychain.

Sharing

• Google: the app connects directly from your iPhone to the Google Health API to read your data, under your account and the permissions you grant.
• Open-Meteo (open-meteo.com): if “Include air pressure” is on, the app sends your coordinates rounded to about 1 km to fetch air pressure. No other data is sent. You can turn this off under More → Migraine risk.

We do not sell data, show ads, use analytics or tracking tools, or share information with third parties for any other purpose.

Use of Google data

Know your Limits’ use and transfer to any other app of information received from Google APIs will adhere to the Google API Services User Data Policy, including the Limited Use requirements. Google data is used solely to show you your own metrics inside the app.

Your choices

• Delete everything: More → Delete all data removes local data and the Google connection. Uninstalling the app also removes it.
• Revoke Google access at any time at myaccount.google.com/permissions.
• Location: deny or remove the permission in iOS Settings → Know your Limits → Location.

This website

knowyourlimits.fit is served through Cloudflare. To pick the page language we use the approximate country of your connection, which Cloudflare derives from your IP address; we do not store it. If you switch languages, a cookie named lang remembers your choice for one year. The site uses no analytics, advertising or other cookies.

Children

The app is not directed to children under 16.

Health notice

Know your Limits is not a medical device. Its metrics are for information only and do not replace advice from a health professional.

Changes and contact

If this policy changes, the new version will be posted on this page. Questions: contact@knowyourlimits.fit.