Mobile device ID

Definition
Mobile device IDs (also called simply Device IDs) are short strings of letters and/or numbers that uniquely identify specific mobile devices. }}

Overview
"Today's smartphones typically have multiple device IDs, each used for a different purpose. Some device IDs are used to enable services like Wi-Fi and Bluetooth, or to uniquely identify specific devices operating on the carriers' networks. Other device IDs, like Apple's 'UDID' or Android's 'Android ID,' are used by apps, developers, and other companies to identify, track, and analyze devices and their users across various mobile services."