Loupe is an iOS and iPadOS app that gives you a hands-on tour of the device fingerprinting surface. It reads real values from public iOS APIs, the same ones any third-party app can call, and shows them to you raw. The point is simple: see what your iPhone quietly exposes, and why each reading helps an app recognize you again.

Trackers don't need your name, email, or location to recognize you online. Each reading isn't necessarily unique on its own, but together they form a fingerprint that follows you across apps and websites.

How signals are organized

Loupe groups every reading into three tiers, reflecting the cost of access:

Passive — visible to any app with no prompt at all (locale, time zone, screen, battery, and more).

Needs Permission — readings that trigger an iOS prompt (contacts, photos, location, calendars).

Advanced — clever side-channel uses of public APIs, such as URL-scheme probing via canOpenURL and Keychain persistence across reinstalls.

Privacy

Nothing Loupe reads leaves your device…