The International Mobile Station Equipment Identity database contains basic information about GSM-based cellular devices associated with a specific 15-digit IMEI identification number, including the phone's manufacturer, brand, model and technical capabilities. The IMEI database also maintains a "blacklist" of phones reported as stolen used to block the stolen phones from accessing cellular networks.
Although the IMEI database contains basic technical information about phones, such as supported radio bands, the primary use of the database is to report stolen phones. A stolen phone blacklisted in the IMEI database does not function on most cellular networks, even if someone removes or replaces the phone's SIM card, because the IMEI identification number is separate from the subscriber identification information contained in the SIM card. It is often prudent to look up a used phone's IMEI number before purchasing it for this reason. The separation of subscriber information from the IMEI database also means it cannot provide information about a phone's current owner.
The IMEI database only contains information for GSM phones. As of 2015, the CDMA phones used by some U.S. cellular companies are not present in the standard IMEI database. However, all 4G phones use the GSM standard and have entries in the IMEI.