Privacy Policy
What we collect, where it goes, and how to get rid of it. Written for humans, not lawyers.
Last updated 26 August 2026. Longevity Stack is operated from the United Kingdom and this policy is written to UK GDPR.
The short version
The calculators on this site run entirely in your browser. The figures you type into them — your age, your weight, your blood results — are never sent to us and never leave your device unless you choose to create an account and save a result. We do not sell data to anyone, and we do not use advertising trackers.
What we collect
Calculator inputs — nothing leaves your browser
Every tool here computes locally. If you use the "save this result" feature, the result is written to your own browser's storage, on your own device. Clearing your browser data removes it and we never see it.
Your email address — only if you give it to us
If you subscribe to the newsletter we store your email address, the date, and which part of the site you subscribed from, so we know which pages people find useful. Nothing else. Every email has a one-click unsubscribe, and unsubscribing is honoured immediately.
Account data — only if you create one
An account stores your email address, an optional display name, and any tool results you explicitly save. This lets your history follow you between devices. Authentication and storage are handled by Supabase.
Analytics — aggregate only, no cookies
We measure how many people visit each page and how many finish each calculator, using cookieless analytics that records no personal data and cannot identify or follow you between sites. That is why this site has no cookie banner: there is nothing to consent to. We do not use Google Analytics.
Health data, specifically
Some of what these tools ask about — biomarkers, medication, smoking — is special category health data under UK GDPR, which is exactly why the tools are built to keep it in your browser. If you save results to an account you are choosing to store that data with us, and you can delete it at any time, permanently, without asking us first.
Photos are the exception, and we say so at the point you upload them. The optional photo assessment sends your photo to an AI service to be analysed — it cannot work any other way. Photos are downscaled on your device before upload, processed to produce the result, and not stored by us; we keep the written result only if you choose to save it to an account, never the image. If you would rather not send a photo anywhere, skip that section — every other part of the assessment works without it.
Who else touches your data
- Supabase — Database, authentication and storage for accounts and newsletter subscribers. EU-hosted.
- Cloudflare — Serves the site and provides network security.
- Analytics provider — Aggregate page and event counts. No personal data, no cookies.
- Email provider — Delivers the newsletter to subscribers who asked for it.
We do not sell, rent or share personal data with advertisers or data brokers. Ever.
How long we keep things
Newsletter addresses are kept until you unsubscribe, then deleted within 30 days. Account data is kept while the account exists and deleted within 30 days of you closing it. Analytics is aggregate and retains no individual record.
Your rights
Under UK GDPR you can ask for a copy of your data, ask us to correct it, ask us to delete it, object to how we use it, or withdraw consent at any time. Email privacy@longevitystack.co.uk and we will respond within 30 days. If you are not satisfied you can complain to the Information Commissioner's Office at ico.org.uk.
Children
This site is not intended for anyone under 18 and we do not knowingly collect data from children.
Changes
If this policy changes materially we will update the date at the top and, where the change affects data we already hold, tell subscribers by email.
See also our medical disclaimer and affiliate disclosure.