Every metric.
One place.
Lack reads your watch, your sleep and your food, merges every wearable into one account, and tells you what to do today. Free, on every device, with your friends.
iPhone and Android apps are coming to the stores. The web app works now on any phone or laptop.
Built for people who want to optimise, not just log.
Rings and scores
Move, Exercise and Stand rings, plus Recovery, Sleep and Strain on 0–100 scales built from your own 28-day baseline.
Every metric with a ?
Forty-plus metrics, from HRV and resting heart rate to VO₂ max, fitness age and sleep debt. Each has a plain-English explainer and a cited source.
One account, every wearable
Apple Watch, Fitbit, Health Connect and manual entries merged and de-duplicated. A watch worn Monday and a different one Tuesday describe the same person.
Focus, not feeds
Every screen leads with the two or three things worth acting on today, then trends, then raw data.
Food without the chore
Quick entry, barcodes, favourites, and a photo of the label that fills the macros in for you to confirm.
Friends and challenges
Mutual requests only. Share rings, workouts and medals, react to each other, run 7-day challenges. Raw vitals never leave your account.
Cycle-aware
Optional period tracking with phase prediction, and recovery read in the context of your phase so a normal luteal week is not scored as a bad one.
Today's session
Rest, mobility, zone 2, tempo, intervals or strength, suggested from recovery, training load, sleep and cycle phase.
Widgets and the web
Date, steps and rings on your lock screen and home screen. The same app, with the same data, in any browser.
Decisions first. Data when you want it.
Rings, lapped like the real thing
Health: focus, trends, then everything
Cycle phase and predictions
Food with label reading
Your data is yours.
Health data is never sold, never used for advertising, and never shared with anyone you have not added as a friend. Delete your account from inside the app and everything goes with it, immediately.
- Scores are deterministic and documented, with sources. No language model touches your numbers.
- Friend sharing is opt-in per category. Cycle data has no share switch at all.
- Export everything as JSON any time.
- Read the privacy policy and terms. They are short.