What is loupe?

Loupe is an iOS and iPadOS app that shows you exactly what data any app on your phone can read about you without asking permission. It pulls real values from the same public iOS system calls that any third-party app can use, and displays them on screen so you can see what your device quietly exposes. The signals are organized into three groups. Passive signals are things any app can read with no prompt at all: your locale, time zone, screen size, battery level, and similar details. Permission-gated signals are readings that iOS asks you about first, such as contacts, photos, location, and calendar access. Advanced signals are more subtle: they use clever ways to extract information from ordinary public APIs, such as testing which URL schemes your phone can open or checking whether data persists in the secure keychain across app reinstalls. The app is educational. Its purpose is to help users understand that trackers do not need a name or email address to recognize a device. Each individual reading may not be unique on its own, but combining many of them creates a fingerprint that can follow a person across apps and websites. Loupe reads nothing, sends nothing off the device, and does not hash or aggregate the values it shows. Loupe is available on the App Store and is open source under the MIT license. Building it from source requires Xcode 26. A macOS version exists but is described as not fully polished yet. The project was made by Mysk, the same team behind a privacy browser called Psylo.