Loupe: Revealing iOS Fingerprinting Signals

Mysk has released Loupe, a free and open-source iOS and iPadOS app that reveals the device fingerprinting signals any third-party app can access through public APIs. The app groups readings into passive, permission-required, and advanced categories, showing users what their iPhone quietly exposes to trackers without uploading or sharing any data. Loupe, built almost entirely with AI coding tools, aims to demonstrate how individual readings combine to form a unique device fingerprint that follows users across apps and websites.

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. 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. Nothing Loupe reads leaves your device unless you explicitly export it. Values are shown raw, without aggregation or hashing. Nothing is uploaded, synced, or shared. Loupe was written almost entirely by AI coding tools. You'll need Xcode 26 or newer. - Open code/Loupe.xcodeproj . - Copy code/Config/Signing.local.xcconfig.example to code/Config/Signing.local.xcconfig and fill in your own DEVELOPMENT TEAM and bundle identifiers. This file is gitignored and never published. - Build and run on a device or simulator. The project uses Xcode's buildable folders folder references , so new Swift files are picked up automatically with no need to edit the project file. Loupe also builds for macOS. The Mac version is mostly complete, but a few things still need work before it's polished. Loupe is free and open source. If it helped you see what apps can quietly learn about your device, the best way to support more work like this is to try Psylo https://apps.apple.com/app/psylo-private-browser-proxy/id6741358035 , our privacy-first browser for iPhone and iPad. Psylo gives you proxy-backed browsing, isolated tabs, and anti-fingerprinting protections. You can also read why we built Psylo https://mysk.blog/2025/06/17/introducing-psylo/ . The source code is released under the MIT License /mysk-research/loupe/blob/main/LICENSE . The Loupe name and logo, the app icon, all other images and icons, and the design source files are © Mysk, all rights reserved, and are not covered by the MIT license. Loupe is made by Mysk.