Clearday: Caffeine & Sleep

About this app

Most caffeine apps tell you how much you've had. Clearday tells you what it's doing to your body. Using your Apple Watch data — sleep score, resting heart rate, and HRV — Clearday calculates your personal caffeine cutoff: the latest time you can have a drink without wrecking your sleep. — HOW IT WORKS Caffeine has a half-life of 5–6 hours. That afternoon coffee at 3pm still leaves 25mg in your bloodstream at 11pm — silently reducing deep sleep. Clearday models this in real time, overlays your HealthKit data, and tells you exactly where your cutoff is. No guesswork. Just your data. — WHAT YOU GET Blood-level curve See your exact caffeine levels across 24 hours — past and predicted. A color-coded line at bedtime shows whether you're in the clear or heading for a rough night. Personal cutoff card After 7 days, Clearday analyzes your sleep scores against your caffeine timing to calculate your personal cutoff time. It updates as your data grows. HealthKit correlation cards - Sleep score — how your total and deep sleep shifts with caffeine intake - Resting heart rate — 7-day trend overlaid with your logging history - HRV — how caffeine-free days affect your heart rate variability Withdrawal timeline (Quit & Reduce modes) Breaking the habit? Clearday shows you a science-backed 9-day timeline — headaches typically peak at day 2, resolve by day 9 — so you know exactly what to expect and when it ends. Log symptoms in one tap and watch them ease off. Three modes - Optimize: Keep drinking coffee. Just stop at the right time. - Reduce: Cut back gradually. Track how your body responds. - Quit: Go caffeine-free. Clearday coaches you through withdrawal. — BUILT ON SCIENCE Clearday's caffeine decay model, cutoff calculations, and withdrawal timeline are based on peer-reviewed research published in Sleep Medicine Reviews, the New England Journal of Medicine, and the Journal of Clinical Sleep Medicine. Full references available in Settings → Science & References. — PRIVACY All HealthKit data stays on your device. Clearday reads sleep, resting heart rate, and HRV — and never shares it with anyone. — PREMIUM Unlock HealthKit correlation cards, personal cutoff insight, withdrawal timeline, and home screen widgets with a Premium subscription. $4.99/month or $34.99/year. Cancel anytime. — From the developer of Soberday: Alcohol & Sleep.

# Japanese Language Support Clearday is now available in Japanese! All screens, notifications, and widgets are fully localized. Your device language setting is automatically detected.

Momentum comes from crawler snapshots for the tracked storefront. “Viral growth signal” means unusually fast recent rating gains; it is an indicator, not download data.

1. First observed Aug 17, 2026 · 10:57 PM Free