Privacy Policy.

RhythmBio is operated by Darryll Stephen, trading as RhythmBio, a sole trader based at 4th Floor, Silverstream House, 45 Fitzroy Street, Fitzrovia, London, W1T 6EB, United Kingdom. For the purposes of UK data protection law, Darryll Stephen is the data controller for the personal data described in this policy.

RhythmBio needs your date of birth to compute your cycles, and an email address so you can sign in. Anything else you give us (journal entries, family members, a calendar feed) exists to make the app useful to you. We never sell your data, we don't run advertising trackers, and you can delete your account and everything in it at any time from Settings.

Account data: your email address and a password (stored only as a secure hash by our authentication provider), plus your first name and date of birth.

Content you create: journal entries (sliders and notes), family members you add (their name, date of birth, and relationship), and, if you connect one, your calendar feed URL and the event titles it exposes.

Subscription data: if you upgrade, payments are processed by Stripe. We never see or store your card number. We store only your Stripe customer reference and subscription status.

Notifications: if you enable push notifications, we store the subscription token your browser generates.

We do not collect analytics identifiers, advertising IDs, or location data.

Your date of birth seeds the biorhythm calculations that power every screen. Your journal and cycle data are used to generate your daily briefings. When AI-written briefings are enabled, the relevant context (your first name, cycle positions, and recent journal signals) is processed by Anthropic's API to write them. Your email address is used for sign-in, account notices, and the daily briefing email if you turn it on.

More generally, we use your data within the app to operate, maintain, and improve the features you're already using — for example, using the family members you add to power Family Hub's coaching, or reviewing aggregated, anonymised usage patterns to see what's actually working and worth improving. This is always in service of running RhythmBio for you, never to profile you for advertising or to hand your data to anyone outside the processors listed below.

Your data is stored with Supabase in the European Union (Ireland, eu-west-1) and encrypted in transit. The app is hosted on Vercel. Emails are sent via Resend. Payments run through Stripe. These providers process data on our behalf and under their own security programmes; none of them are permitted to use your data for their own purposes.

We don't sell your data. We don't share it with advertisers. We don't use third-party analytics trackers or advertising cookies. The only cookies we set are the ones that keep you signed in.

We process your account data and content because it's necessary to provide the service you've signed up for (performance of a contract). Where you opt in to something separable, like the daily briefing email, we rely on your consent, which you can withdraw at any time from Settings. We keep your data for as long as your account is active, and delete it (alongside anything derived from it) when you delete your account or, for accounts left inactive, no more than 24 months after your last sign-in.

You can access and correct your profile in Settings at any time. Deleting your account from Settings permanently removes your profile, journal entries, family members, briefings, and push subscriptions. You also have the right to request a copy of your data, or to ask us to correct or erase it. Email us and we'll act on it promptly. If you're not satisfied with how we've handled a request, you have the right to complain to the UK's data protection regulator, the Information Commissioner's Office (ico.org.uk).

Some of our processors (including Anthropic, who help write the AI daily briefings) operate in the United States. Where your data is transferred outside the UK, we rely on standard contractual safeguards recognised under UK data protection law to keep it protected to the same standard.

RhythmBio is not intended for children under 16. If you believe a child has created an account, contact us and we'll remove it.

If this policy changes materially, we'll note the new date at the top of this page and, for significant changes, tell you by email. Questions or requests: hi@rhythmbio.app, or by post to Darryll Stephen, 4th Floor, Silverstream House, 45 Fitzroy Street, Fitzrovia, London, W1T 6EB, United Kingdom.