Is there a unique Android device ID?

Settings.Secure#ANDROID_ID returns the Android ID as an unique 64-bit hex string.

import android.provider.Settings.Secure;

private String android_id = Secure.getString(getContext().getContentResolver(),
                                                        Secure.ANDROID_ID); 

There are many answers to this question, most of which will only work "some" of the time, and unfortunately that's not good enough.

Based on my tests of devices (all phones, at least one of which is not activated):

So if you want something unique to the device itself, TM.getDeviceId() should be sufficient. Obviously some users are more paranoid than others, so it might be useful to hash 1 or more of these identifiers, so that the string is still virtually unique to the device, but does not explicitly identify the user's actual device. For example, using String.hashCode(), combined with a UUID:

    final TelephonyManager tm = (TelephonyManager) getBaseContext().getSystemService(Context.TELEPHONY_SERVICE);

    final String tmDevice, tmSerial, androidId;
    tmDevice = "" + tm.getDeviceId();
    tmSerial = "" + tm.getSimSerialNumber();
    androidId = "" + android.provider.Settings.Secure.getString(getContentResolver(), android.provider.Settings.Secure.ANDROID_ID);

    UUID deviceUuid = new UUID(androidId.hashCode(), ((long)tmDevice.hashCode() << 32) | tmSerial.hashCode());
    String deviceId = deviceUuid.toString();

might result in something like: 00000000-54b3-e7c7-0000-000046bffd97

It works well enough for me.

As Richard mentions below, don't forget that you need permission to read the TelephonyManager properties, so add this to your manifest:

<uses-permission android:name="android.permission.READ_PHONE_STATE" />

As Dave Webb mentions, the Android Developer Blog has an article that covers this. Their preferred solution is to track app installs rather than devices, and that will work well for most use cases. The blog post will show you the necessary code to make that work, and I recommend you check it out.

However, the blog post goes on to discuss solutions if you need a device identifier rather than an app installation identifier. I spoke with someone at Google to get some additional clarification on a few items in the event that you need to do so. Here's what I discovered about device identifiers that's NOT mentioned in the aforementioned blog post:

Based on Google's recommendations, I implemented a class that will generate a unique UUID for each device, using ANDROID_ID as the seed where appropriate, falling back on TelephonyManager.getDeviceId() as necessary, and if that fails, resorting to a randomly generated unique UUID that is persisted across app restarts (but not app re-installations).

Note that for devices that have to fallback on the device ID, the unique ID WILL persist across factory resets. This is something to be aware of. If you need to ensure that a factory reset will reset your unique ID, you may want to consider falling back directly to the random UUID instead of the device ID.

Again, this code is for a device ID, not an app installation ID. For most situations, an app installation ID is probably what you're looking for. But if you do need a device ID, then the following code will probably work for you.

import android.content.Context;
import android.content.SharedPreferences;
import android.provider.Settings.Secure;
import android.telephony.TelephonyManager;

import java.io.UnsupportedEncodingException;
import java.util.UUID;

public class DeviceUuidFactory {
    protected static final String PREFS_FILE = "device_id.xml";
    protected static final String PREFS_DEVICE_ID = "device_id";

    protected static UUID uuid;



    public DeviceUuidFactory(Context context) {

        if( uuid ==null ) {
            synchronized (DeviceUuidFactory.class) {
                if( uuid == null) {
                    final SharedPreferences prefs = context.getSharedPreferences( PREFS_FILE, 0);
                    final String id = prefs.getString(PREFS_DEVICE_ID, null );

                    if (id != null) {
                        // Use the ids previously computed and stored in the prefs file
                        uuid = UUID.fromString(id);

                    } else {

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

                        // Use the Android ID unless it's broken, in which case fallback on deviceId,
                        // unless it's not available, then fallback on a random number which we store
                        // to a prefs file
                        try {
                            if (!"9774d56d682e549c".equals(androidId)) {
                                uuid = UUID.nameUUIDFromBytes(androidId.getBytes("utf8"));
                            } else {
                                final String deviceId = ((TelephonyManager) context.getSystemService( Context.TELEPHONY_SERVICE )).getDeviceId();
                                uuid = deviceId!=null ? UUID.nameUUIDFromBytes(deviceId.getBytes("utf8")) : UUID.randomUUID();
                            }
                        } catch (UnsupportedEncodingException e) {
                            throw new RuntimeException(e);
                        }

                        // Write the value out to the prefs file
                        prefs.edit().putString(PREFS_DEVICE_ID, uuid.toString() ).commit();

                    }

                }
            }
        }

    }


    /**
     * Returns a unique UUID for the current android device.  As with all UUIDs, this unique ID is "very highly likely"
     * to be unique across all Android devices.  Much more so than ANDROID_ID is.
     *
     * The UUID is generated by using ANDROID_ID as the base key if appropriate, falling back on
     * TelephonyManager.getDeviceID() if ANDROID_ID is known to be incorrect, and finally falling back
     * on a random UUID that's persisted to SharedPreferences if getDeviceID() does not return a
     * usable value.
     *
     * In some rare circumstances, this ID may change.  In particular, if the device is factory reset a new device ID
     * may be generated.  In addition, if a user upgrades their phone from certain buggy implementations of Android 2.2
     * to a newer, non-buggy version of Android, the device ID may change.  Or, if a user uninstalls your app on
     * a device that has neither a proper Android ID nor a Device ID, this ID may change on reinstallation.
     *
     * Note that if the code falls back on using TelephonyManager.getDeviceId(), the resulting ID will NOT
     * change after a factory reset.  Something to be aware of.
     *
     * Works around a bug in Android 2.2 for many devices when using ANDROID_ID directly.
     *
     * @see http://code.google.com/p/android/issues/detail?id=10603
     *
     * @return a UUID that may be used to uniquely identify your device for most purposes.
     */
    public UUID getDeviceUuid() {
        return uuid;
    }
}

Also you might consider the WiFi adapter's MAC address. Retrieved thusly:

WifiManager wm = (WifiManager)Ctxt.getSystemService(Context.WIFI_SERVICE);
return wm.getConnectionInfo().getMacAddress();

Requires permission android.permission.ACCESS_WIFI_STATE in the manifest.

Reported to be available even when WiFi is not connected. If Joe from the answer above gives this one a try on his many devices, that'd be nice.

EDIT: on some devices, it's not available when WiFi is turned off.

The official Android Developers Blog now has a full article just about this very subject:

http://android-developers.blogspot.com/2011/03/identifying-app-installations.html

Here is the code that Reto Meier used in the google i/o presentation this year to get a unique id for the user:

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;
}

If you couple this with a backup strategy to send preferences to the cloud (also described in Reto's talk, you should have an id that ties to a user and sticks around after the device has been wiped, or even replaced. I plan to use this in analytics going forward (in other words I have not done that bit yet :).

There’s rather useful info here.

It covers five different ID types:

String serial = null; 

try {
    Class<?> c = Class.forName("android.os.SystemProperties");
    Method get = c.getMethod("get", String.class);
    serial = (String) get.invoke(c, "ro.serialno");
} catch (Exception ignored) {
}

This code returns device serial number using hidden Android API. But, this code don't works on Samsung Galaxy Tab because "ro.serialno" isn't set on this device.

I think this is sure fire way of building a skeleton for a unique ID... check it out.

Pseudo-Unique ID, that works on all Android devices Some devices don't have a phone (eg. Tablets) or for some reason you don't want to include the READ_PHONE_STATE permission. You can still read details like ROM Version, Manufacturer name, CPU type, and other hardware details, that will be well suited if you want to use the ID for a serial key check, or other general purposes. The ID computed in this way won't be unique: it is possible to find two devices with the same ID (based on the same hardware and rom image) but the chances in real world applications are negligible. For this purpose you can use the Build class:

String m_szDevIDShort = "35" + //we make this look like a valid IMEI
            Build.BOARD.length()%10+ Build.BRAND.length()%10 +
            Build.CPU_ABI.length()%10 + Build.DEVICE.length()%10 +
            Build.DISPLAY.length()%10 + Build.HOST.length()%10 +
            Build.ID.length()%10 + Build.MANUFACTURER.length()%10 +
            Build.MODEL.length()%10 + Build.PRODUCT.length()%10 +
            Build.TAGS.length()%10 + Build.TYPE.length()%10 +
            Build.USER.length()%10 ; //13 digits

Most of the Build members are strings, what we're doing here is to take their length and transform it via modulo in a digit. We have 13 such digits and we are adding two more in front (35) to have the same size ID like the IMEI (15 digits). There are other possibilities here are well, just have a look at these strings. Returns something like: 355715565309247 . No special permission are required, making this approach very convenient.

(Extra info: The technique given above was copied from an article on Pocket Magic.)

A Serial field was added to the Build class in API level 9 (android 2.3). Documentation says it represents the hardware serial number. thus it should be unique, if it exists on the device.

I don't know whether it is actually supported (=not null) by all devices with API level >= 9 though.

String deviceId = Settings.System.getString(getContentResolver(),Settings.System.ANDROID_ID);

Using above code you can get a Unique device ID of Android OS Device as String.

For detailed instructions on how to get a Unique Identifier for each Android device your application is installed from, see this official Android Developers Blog posting:

http://android-developers.blogspot.com/2011/03/identifying-app-installations.html

It seems the best way is for you to generate one your self upon installation and subsequently read it when the application is re-launched.

I personally find this acceptable but not ideal. No one identifier provided by Android works in all instances as most are dependent on the phone's radio states (wifi on/off, cellular on/off, bluetooth on/off). The others like Settings.Secure.ANDROID_ID must be implemented by the manufacturer and are not guaranteed to be unique.

The following is an example of writing data to an INSTALLATION file that would be stored along with any other data the application saves locally.

public class Installation {
    private static String sID = null;
    private static final String INSTALLATION = "INSTALLATION";

    public synchronized static String id(Context context) {
        if (sID == null) {  
            File installation = new File(context.getFilesDir(), INSTALLATION);
            try {
                if (!installation.exists())
                    writeInstallationFile(installation);
                sID = readInstallationFile(installation);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        return sID;
    }

    private static String readInstallationFile(File installation) throws IOException {
        RandomAccessFile f = new RandomAccessFile(installation, "r");
        byte[] bytes = new byte[(int) f.length()];
        f.readFully(bytes);
        f.close();
        return new String(bytes);
    }

    private static void writeInstallationFile(File installation) throws IOException {
        FileOutputStream out = new FileOutputStream(installation);
        String id = UUID.randomUUID().toString();
        out.write(id.getBytes());
        out.close();
    }
}

One thing I'll add - I have one of those unique situations.

Using:

deviceId = Secure.getString(this.getContext().getContentResolver(), Secure.ANDROID_ID);

Turns out that even though my Viewsonic G Tablet reports a DeviceID that is not Null, every single G Tablet reports the same number.

Makes it interesting playing "Pocket Empires" which gives you instant access to someone's account based on the "unique" DeviceID.

My device does not have a cell radio.

How about the IMEI. That is unique for Android or other mobile devices.