Last updated: May 8, 2026
These terms govern your use of the Onyx iOS 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 tracking app for iPhone. It reads metrics from Apple Health, computes a daily recovery score, generates training and nutrition guidance, 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. The only login involved is your Apple ID, which is used by Apple for In-App Purchases — we never see it.
Onyx asks for permission to read and write specific Apple Health metrics. You grant or revoke that permission inside iOS Settings. Onyx cannot function as designed without read access — but you control what's shared.
Pro is offered as a monthly subscription, an annual subscription, or a one-time lifetime purchase. Prices are displayed inside the app and may change. All transactions go through Apple's In-App Purchase system; Apple's terms govern the purchase, refund, and renewal flow.
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. If you want a refund, request one through Apple's standard process.
Grandfathered Pro: Users who had any version of Onyx installed before v2.0 receive Pro for life at no cost. This is a courtesy and may be withdrawn if abused (creating multiple installs to game grandfathering).
Don't try to break the app, reverse engineer it, or use it for anything that violates the law. Don't use Coach to ask for help with anything illegal, harmful, or that would violate Anthropic's usage policies.
Coach is powered by an AI model and may produce inaccurate or incomplete responses. Treat its output as a thoughtful starting point, not a final answer. We don't guarantee that any specific advice from Coach is correct, complete, or appropriate for your situation.
Nothing in Onyx is medical advice. The recovery score, illness warnings, training recommendations, 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.