Built on real research
66 days is the median time habits take to form, not 21 — a number that traces back to peer-reviewed research, not a decades-old myth.
It gets you 66% of the way. That's why the myth feels true — and why it fails you anyway. 66 Habits is built on the real science: 66 repetitions, proof you actually did it, and an app that gets quieter as you get better.
Illustrative — not an in-app screenshot.
Lally et al. (2010) found habits took a median of 66 days to form, ranging from 18 to 254. 66 Habits is built around that curve, one credited repetition at a time.
66 days is the median time habits take to form, not 21 — a number that traces back to peer-reviewed research, not a decades-old myth.
Daily, specific days, or times per day — every habit is 66 credited repetitions, with a maximum of one credited rep per day.
Write one line about what you did, or attach a photo. Proof is required early on and becomes optional once you're over the hump.
Not your progress. Missing a day never erases what you've built — the count keeps going, it just takes a little longer.
Habit strength rises fast at first, then levels off. The app asks less of you as the habit needs less of you.
Today's habits and your progress, visible without opening the app.
66 Habits collects no personal data. Everything you enter stays on your device and, if you choose, syncs privately through your own iCloud account. No accounts, no analytics, no ads.