Cross-browser anonymity is something that the conscious Internet user takes for granted. The Tor browser offers maximum privacy protection, but even it, as it turns out, does not guarantee complete anonymity. The site creates a profile of the apps installed on the device to perform cross-browser tracking, trying to open them using URL handlers. In this case, a check occurs, and if the browser processes the link and offers to open the corresponding application, this means that the application is installed.
Since the applications installed on the device act the same regardless of the browser used, this allows you to track user actions in both Google Chrome, Firefox, and anonymous Tor. Using this script, 24 apps can be tracked: Skype, Spotify, Zoom, vscode, Epic Games, Telegram, Discord, Slack, Steam, Battle.net, Xcode, NordVPN, Sketch, TeamViewer, Microsoft Word, WhatsApp, Postman, Adobe, Messenger, Figma, Hotspot Shield, ExpressVPN, Notion, and iTunes. Many users probably have several applications from this list installed, which will allow them to create a unique ID.