When you change your AID, apps instantly link it to your old AID using several techniques: 1. Nearly every app stores an ID identifying installation of the app

When you change your AID, apps instantly link it to your old AID using several techniques: 1. Nearly every app stores an ID identifying installation of the app on your phone. When the app starts up, it sends this installation ID and your new AID to the server which now has both old and new AID. To prevent this, you must uninstall all apps, change your AID, and then reinstall apps. Deleting app data is insufficient because app install times are unique and easily obtained from app file timestamps. Android apps that have access to "external storage" will send file hashes to the server and identify you instantly. 2. When you sign into an app, it sends your IDs to the server which now has your old and new AID. 3. If you use an app that talks to a physical device, the physical device reports its serial number or unique network address. The app sends this to the server with your new AID. Any app can silently search for such devices on your network and extract their ID numbers. Examples of physical devices: fitness bands, anything BlueTooth, printers, remote-controlled lights, NFC tokens, and find-my-keys tokens. 4. If you use WiFi without a shared proxy (a VPN) then any app or even any website can simply send your (device type, IP address) pair to the ad network for de-anonymizing. No need for IDs at all. The moment you launch any ad-supported app on such a non-proxied Internet connection, the app will link your new AID to your identity. This happens when you connect to Wifi at work or friends' homes. Most VPN software fails open, so apps can get your IP address for a few seconds when the phone restarts and every time the VPN service is down or momentarily interrupted. Working around this takes knowledge and effort. Once one app company sells your (Old AID, New AID) pair, this data enters the network of data brokers and is available to all. TLDR: Changing your AID alone does nothing. Mobile privacy requires a fail-closed shared proxy (VPN), no data sharing between apps, and no reachable devices on the WiFi network.