[android] Is Secure.ANDROID_ID unique for each device?

There are multiple solution exist but none of them perfect. let's go one by one.

1. Unique Telephony Number (IMEI, MEID, ESN, IMSI)

• This solution needs to request for android.permission.READ_PHONE_STATE to your user which can be hard to justify following the type of application you have made.

• Furthermore, this solution is limited to smartphones because tablets don’t have telephony services. One advantage is that the value survives to factory resets on devices.

2. MAC Address

• You can also try to get a MAC Address from a device having a Wi-Fi or Bluetooth hardware. But, this solution is not recommended because not all of the device have Wi-Fi connection. Even if the user have a Wi-Fi connection, it must be turned on to retrieve the data. Otherwise, the call doesn’t report the MAC Address.

3. Serial Number

• Devices without telephony services like tablets must report a unique device ID that is available via android.os.Build.SERIAL since Android 2.3 Gingerbread. Some phones having telephony services can also define a serial number. Like not all Android devices have a Serial Number, this solution is not reliable.

4. Secure Android ID

• On a device first boot, a randomly value is generated and stored. This value is available via Settings.Secure.ANDROID_ID . It’s a 64-bit number that should remain constant for the lifetime of a device. ANDROID_ID seems a good choice for a unique device identifier because it’s available for smartphones and tablets.

  String androidId = Settings.Secure.getString(getContentResolver(),Settings.Secure.ANDROID_ID);
  

• However, the value may change if a factory reset is performed on the device. There is also a known bug with a popular handset from a manufacturer where every instance have the same ANDROID_ID. Clearly, the solution is not 100% reliable.

5. Use UUID

• As the requirement for most of applications is to identify a particular installation and not a physical device, a good solution to get unique id for an user if to use UUID class. The following solution has been presented by Reto Meier from Google in a Google I/O presentation :

  private static String uniqueID = null;
  private static final String PREF_UNIQUE_ID = "PREF_UNIQUE_ID";
  public synchronized static String id(Context context) {
     if (uniqueID == null) {
         SharedPreferences sharedPrefs = context.getSharedPreferences(
                 PREF_UNIQUE_ID, Context.MODE_PRIVATE);
         uniqueID = sharedPrefs.getString(PREF_UNIQUE_ID, null);
         if (uniqueID == null) {
             uniqueID = UUID.randomUUID().toString();
             Editor editor = sharedPrefs.edit();
             editor.putString(PREF_UNIQUE_ID, uniqueID);
             editor.commit();
         }
     }    return uniqueID;
  }
  

Identify a particular device on Android is not an easy thing. There are many good reasons to avoid that. Best solution is probably to identify a particular installation by using UUID solution. credit : blog