Comment by barathr

The IMSI. We don't do anything with the IMEI ourselves (it's in the category of hardware identifiers that I'm mentioning above). Some phones can change them when rooted, some can't. The network attach process doesn't use the IMEI inherently by spec, but some cell cores can query for it (for example, to block stolen phones). It's not a network identifier, and strange things sometimes happen with the IMEI that don't even affect connectivity -- https://www.androidauthority.com/duplicate-imei-vivo-india-1...