Privacy Policy

1. Who we are

OPSIN is operated by ZHC Labs Pte Ltd (Singapore) ("OPSIN", "we", "us"). We provide a sunlight, vitamin D and circadian light tracking app and website (theopsin.com). This policy explains what we collect and how we handle it, consistent with Singapore's Personal Data Protection Act (PDPA) and, where applicable, the GDPR/CCPA. Contact: hello@theopsin.com.

2. The website and the app are different

Two things live under this policy, and they behave very differently. It matters which one you're using.

• This website (theopsin.com) — the science library, the guides, the methodology page, the FAQ and the sunlight estimator on the home page. There is no account and no profile here. We use PostHog to count page views and see which research people find useful — the same single analytics tool we use across all our sites, so we are not spreading your data around more services than necessary. It is configured so that anonymous visitors are never given a person profile (person_profiles: "identified_only"), we do not record your screen or session, and we run no advertising trackers and no cross-site tracking of any kind. We load no third-party fonts or content-delivery assets. The estimator itself runs entirely in your browser: the city, date, skin type and other values you choose are used to do the arithmetic on your device and are never transmitted to us or to anyone else — we see that the page was viewed, not what you typed into it.
• The web app (app.theopsin.com) — the tracker itself. This requires an account, stores your data in our cloud so it syncs across devices, and uses product analytics. Everything in sections 3 to 8 below is about the app unless it says otherwise.

Our hosting provider (Cloudflare) processes standard technical request data — such as IP address and browser type — to serve pages and block abuse, as any web host must. We do not use it to build a profile of you.

3. Data we process

• Account: when you sign in to the web app, our authentication provider (Clerk) processes your email and/or Google/Apple sign-in identity to create your account. We identify your data by your account ID.
• Profile you provide: skin type, birth year/age, optional BMI, wake and bed times, clothing/exposure, supplement dose, goals, and preferences. Used to personalize your estimates. On the web app, this is stored in our cloud database (see §4) under your account so it syncs across your devices.
• Activity you log: sun sessions, supplement entries, blood-test results you enter, streaks. On the web app, stored in our cloud database under your account (with a local browser cache for offline use).
• Location: your approximate coordinates, used to calculate sun position and fetch your local UV/weather forecast. Coordinates (or a city name you search) are sent to our forecast provider (Open-Meteo) for this purpose.
• AI coach: if you use the coach, the messages you send and a snapshot of your current OPSIN data (scores, plan) are sent to our LLM provider (Flow AI) to generate a reply, and the exchange may be logged for safety and quality. Don't put information in the coach you don't want processed this way.
• Apple Health / device health data (iOS app, optional): with your explicit permission, the iOS app may read data such as time in daylight, sleep, and body metrics, and write your estimated vitamin D / light-exposure sessions back to Health. Raw HealthKit data stays on your device; only derived aggregates sync, with consent.
• Camera ("mirror" feature, iOS, optional): used on-device only to estimate light level and exposed skin. Images are processed on your device and are not stored or uploaded.
• Product analytics & error reporting: we use PostHog to understand how features are used (pages viewed, buttons tapped, feature usage) and to capture technical errors so we can fix them. You are identified only by your opaque account ID — not your name or email. Values you type into forms are masked, and we do not record your screen or session. See §4.

4. Cookies and local storage

• On this website: our analytics provider (PostHog) sets a first-party cookie so a series of page views can be counted as one visit rather than many. It is used only to measure how the site is read. We set no advertising cookies, and nothing here is shared with ad networks or used to follow you across other websites.
• In the web app: our authentication provider (Clerk) uses a session cookie to keep you signed in — this is strictly necessary for the app to work and cannot be turned off while you're logged in. The app also uses your browser's local storage to cache your own data for offline use; you can clear it from your browser settings or with Settings → Reset all data.
• Security: Cloudflare may set a short-lived cookie to distinguish humans from bots.

Links out to research. The library cites primary sources — PubMed, PMC, Nature, the WHO and others. Those are ordinary outbound links: nothing is sent to them unless you choose to click, at which point you are on their site under their privacy policy, not ours.

Our standard. We deliberately use one analytics tool across every site we run rather than accumulating several — fewer processors means fewer places your data can go. If that ever changes we will say so plainly here and update the effective date above before it goes live.

5. What we do NOT do

• We do not sell your personal data.
• We do not use your data for third-party advertising.
• We do not upload raw camera images or raw Apple Health data from the iOS app.

6. Third-party processors

We use these providers to run the service; each processes only what's needed for its function:

• Clerk — authentication / account management.
• Railway — application hosting and the PostgreSQL database that stores your web-app data.
• Cloudflare — DNS, hosting for this website, content delivery and security; processes technical request data (IP, browser type) to serve pages and block abuse.
• Open-Meteo — UV/weather forecasts and geocoding (receives coordinates or a city name).
• Flow AI — the LLM that powers the coach (receives coach messages + your data snapshot).
• PostHog (US region) — analytics for this website and the web app; receives usage events and errors keyed to your opaque account ID, with typed input values masked.

7. Storage, security & retention

Web-app data is stored in our cloud database (Railway PostgreSQL), associated with your account and protected in transit and at rest by our providers' security. A copy may be cached in your browser for offline use. We retain your data while your account is active; when you delete your data or account, it is removed from our active database. Use the in-app export before deleting.

8. Your choices & rights

• You can revoke location, camera, and Health permissions at any time in your device/browser settings.
• You can export your data (Settings → Data) and delete all of it (Settings → Reset all data), or contact us to delete your account and associated data.
• Depending on where you live (e.g. Singapore PDPA, EEA/UK GDPR, California CCPA), you may have rights to access, correct, delete, or port your personal data — contact hello@theopsin.com.

9. Children

OPSIN is not directed to children under 13 (or the minimum age in your country), and we do not knowingly collect their data.

10. Changes

We may update this policy; we'll change the effective date above and, for material changes, notify you in the app.