Is Helix free?
The core loop, recovery, strain, sleep and stress, is free forever, with no account and no trial clock. Helix Pro adds the deeper labs: VO₂max Lab, Training Lab, bloodwork, experiments, the energy schedule and the AI coach. The getting started page has the full free-vs-Pro table.
Do I need an Apple Watch?
No, but you get much more with one. Without a watch, sleep falls back to iPhone motion detection and is honestly labeled as an estimate, and anything that needs heart-rate presence says so instead of guessing. With a watch you get the full overnight vitals, live strain and the wrist app. The with & without a watch page has the exact breakdown.
How is this different from WHOOP, Bevel or Athlytic?
Three structural differences: no new hardware (Helix runs on the watch and phone you already own), no subscription wall on the core loop, and no accounts (everything is computed on your iPhone). Beyond that, Helix goes deeper than wrist-only products in specific places: bloodwork panels scored marker by marker, muscle-level recovery from every set you log, and a VO₂max lab with field tests and race predictions.
Is my health data safe?
Helix has no backend and no account, so there is no server-side copy of your health data to breach. Scores are computed and stored on your iPhone, and raw Apple Health samples are never uploaded. The privacy page walks through the whole architecture.
Why is my score different from my friend’s with the same sleep?
Because you are scored against your own baselines, not theirs and not a population average. The same night of sleep and the same HRV reading can be above one person’s normal and below another’s. Helix also learns over time which signals predict your good and bad days, so the weighting itself diverges between people. Both scores are right.
Does it work with Android?
No. Helix is built on Apple Health and runs on iPhone and Apple Watch only.
What happens if I skip a night?
No score that morning. Helix does not invent a number from a missing night; the gap shows as a gap and scoring resumes with the next recorded night. Your baselines carry on unharmed, so a skipped night costs you a morning, not your calibration.
Can I export my data?
The underlying health data lives in Apple Health, which exports everything from the Health app whenever you want. It was always yours; Helix reads it rather than owning it.
Why does my day start when I wake up?
Because midnight is an accounting convention, not a biological one. Helix rolls your day when you wake from your main sleep, which keeps a late-night workout on the day you actually did it and stops strain from resetting mid-evening. The sleep-anchored day page explains it.
Does the AI coach see my personal data?
It receives anonymized numbers only: your scores and metrics, never your identity, name or raw Apple Health samples. Nothing is stored server-side by Helix, because Helix has no server. Details on the AI coach and privacy pages.
How long until scores are accurate?
Scores are useful from the first mornings, but they carry a visible confidence indicator while your baselines build, and calibration strengthens over the first weeks of data. The baselines & confidence page covers the calibration period.
Will wearing my watch overnight kill the battery?
Sleep tracking uses relatively little battery; the real question is when to charge. The pattern that works: top up during your morning routine and again during your evening wind-down. Two short charging windows a day cover overnight wear comfortably, and the watch stays on your wrist for the night that matters most.
Why did my score drop when I feel fine?
The overnight signals often move before you feel anything; a shift in resting heart rate or HRV can precede illness or accumulated fatigue by a day or two. If the feeling and the score keep disagreeing, rate your days in the app: that feedback is exactly what Helix uses to re-weight the signals toward how your days actually go.