IMEI blacklist is a database of mobile devices that are reported lost, stolen, or involved in illegal activities. Once blacklisted, the phone cannot connect to any cellular network.
Who maintains blacklist? In India, CEIR (Central Equipment Identity Register) maintains the national blacklist. All operators (Airtel, Jio, Vi, BSNL) sync with CEIR.
What happens after blacklisting? When someone inserts a SIM, the network checks IMEI against blacklist and rejects service. Phone becomes useless for calling, SMS, mobile data.
Can blacklisted phone be used on Wi-Fi? Yes, Wi-Fi and offline functions still work. Only cellular services are blocked.
How long does blacklist last? Permanently unless unblocked by owner after recovery.
International blacklist: Indian blacklist is shared with GSMA, so phone may be blocked in other countries too.