X-Marks Privacy Policy

Last updated 25 July 2026

X-Marks is a family app for making and playing real-world GPS treasure hunts. It is built so that we collect nothing: there are no accounts, no analytics, no advertising, and no app servers.

What the app stores, and where

• Hunts you make or receive (names, prize descriptions, map points, and your progress) are stored only on your device, in the app's private storage, protected by iOS data protection (encrypted at rest until the device is first unlocked).
• Your location and compass heading are used live, on the device, to guide you to treasure points while the app is open. They are never recorded, stored, or transmitted anywhere.

How sharing works

When you share a hunt, the entire hunt travels inside the link or file itself — there is no server holding it. Before it leaves your phone, the hunt is compressed and encrypted (AES-256-GCM, with the key derived inside the app using a hash-key scheme), so the messaging service carrying it, link-preview servers, and anyone who intercepts the message see only unreadable ciphertext. Only the X-Marks app can decrypt it. Because the key ships inside the app, this protects hunts in transit between copies of the app; treat hunt links like the family messages they travel in.

You choose who to send hunts to, using your own messaging apps (iMessage, WhatsApp, etc.). Those services handle the message under their own privacy policies.

This website

This site is a static page hosted on GitHub Pages. It exists to describe the app and to catch hunt links opened on phones without the app installed. It runs no analytics and sets no cookies. The encrypted hunt code in a link stays in your browser — this site never reads, stores, or transmits it. GitHub may keep standard web-server logs (such as IP addresses) as described in GitHub's privacy statement.

Third parties

• Apple Maps provides the map imagery in the app, under Apple's privacy policy.
• There are no other third parties. No data is sold or shared — the app has no data to sell.

Children

X-Marks is made for families. Because the app collects and transmits no personal data, there is nothing gathered about children (or anyone else). Hunts reach a child's phone only when someone — normally a parent — sends them one directly.

Changes

If the app ever changes how it handles data, this page will be updated before that version ships.

Contact

Questions? Email paulrobinson010@gmail.com.

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