Last updated: August 18, 2026
These terms govern your use of the Onyx iOS and watchOS app, made by TheMillerBrand. By using Onyx, you agree to them. If you don't agree, don't use the app.
Onyx is a personal health, fitness, and nutrition app for iPhone and Apple Watch. It reads metrics from Apple Health, computes a daily recovery score, generates training and nutrition guidance, reads imported bloodwork, and offers an AI coach that reasons against your current state. It is not a medical device, not a diagnostic tool, and not a replacement for a clinician.
There is no Onyx account. Your data lives on your iPhone. If you choose to sign in with Apple, Onyx syncs your data to your own private iCloud database using Apple's CloudKit — we can't read it, and we don't hold a copy. Apple's In-App Purchase system handles payment; we never see your payment details.
Onyx asks permission to read and write specific Apple Health metrics, in two stages — a core set at setup and a smaller second request the first time you open the Body tab. You grant or revoke each one in iOS Settings. Onyx can't function as designed without read access, but you decide what's shared, and the app degrades honestly rather than inventing numbers it can't measure.
Pro is offered as a monthly subscription, an annual subscription, or a one-time lifetime purchase. Prices are shown in the app and may change. All transactions go through Apple's In-App Purchase system; Apple's terms govern purchase, refund, and renewal.
Subscriptions auto-renew unless you turn off auto-renewal at least 24 hours before the period ends. Manage or cancel in iOS Settings → your name → Subscriptions.
Refunds are handled by Apple. Request one through Apple's standard process at reportaproblem.apple.com.
Grandfathered Pro: anyone who had a version of Onyx installed before v2.0 receives Pro for life at no cost. This is a courtesy and may be withdrawn if abused — for example, creating multiple installs to game it.
Don't try to break the app, reverse engineer it, or use it for anything unlawful. Don't use Coach to ask for help with anything illegal or harmful, or anything that would violate Anthropic's usage policies.
Coach, food photo parsing, menu reading, bloodwork extraction, and the written narratives are all powered by an AI model and may produce inaccurate or incomplete results. Treat them as a thoughtful starting point, not a final answer.
Bloodwork extraction in particular reads numbers off an image. Check the values against your original lab report before acting on anything — Onyx shows you the extracted panel for review before it saves, and that review step exists for a reason.
Nothing in Onyx is medical advice. The recovery score, illness early-warning, heart-rhythm notifications surfaced from Apple Health, training recommendations, bloodwork readings, and Coach replies are signal — not diagnosis, not prescription. If something feels wrong, see a clinician. We are not liable for decisions you make based on Onyx's output. See the Medical Disclaimer for the longer version.