There are many occasions where knowing the unique identifier of your device is very convenient.
For example, to grant exclusive access to the app if installed on specific devices.
Or to keep track of installations of the app.
Unlike other platforms, Android NOT defines a REAL unique identifier.
However, there are a number of identifiers that can be retrieved from the device, but each of these has its pros and cons and no one is absolutely reliable.
The app MyID offers quickly a series of identifiers of your own device which may be disclosed for the purposes set out above.
In particular, the app shows:
More specifically, Settings.Secure.ANDROID_ID.
A 64-bit number (as a hex string) that is randomly generated on the device's first boot and should remain constant for the lifetime of the device (The value may change if a factory reset is performed on the device.) ANDROID_ID seems a good choice for a unique device identifier.
IMEI, MEID, ESN, IMSI:
IMEI( International Mobile Equipment Identity )
The unique number to identify GSM, WCDMA mobile phones as well as some satellite phones
MEID(Mobile Equipment IDentifier)
The globally unique number identifying a physical piece of CDMA mobile station equipment, the MEID was created to replace ESNs(Electronic Serial Number)
ESN(Electronic Serial Number)
The unique number to identify CDMA mobile phones
IMSI(International Mobile Subscriber Identity)
The unique identification associated with all GSM and UMTS network mobile phone users
Serial Number can be identified for the devices such as MIDs (Mobile Internet Devices) or PMPs (Portable Media Players) which are not having telephony services.