Have you ever come across the term UDID when working with an Android device? You may have needed to provide it to install a beta version of an application, register with a corporate system, or test software. Although this identifier is not as widely known as IMEI or serial number, it plays an important role in the Android ecosystem - especially for developers, system administrators and users working with custom scenarios.

Unlike Applewhere UDID (Unique Device Identifier) was officially deprecated in 2013 due to privacy concerns, the term is still used on Android, but often under different names - (Google Advertising ID) or even ANDROID_ID, SSAID (Google Advertising ID) or even build.serial. In this article, we will figure out what UDID is on Android, how to find it (including without root access), how it differs from other identifiers, and why services like Firebase, Xamarin or corporate MDM systems sometimes require it.

Spoiler: on modern versions of Android, a “pure” UDID in the usual sense no longer exists - instead, combinations of several identifiers are used. But more on this later.

What is UDID on Android and why do you need it?

UDID (Unique Device Identifier) is a unique code assigned to each mobile device. Historically, it was a 40-digit hash, tightly tied to the hardware ( iOS it was a 40-digit hash, tightly tied to the hardware (hardware-based). There is no similar role on Android, but the term “UDID” is often used to refer to any stable device identifier that:

  • 🔹 Does not change after resetting the settings (factory reset)
  • 🔹 Tied to the hardware, not to the Google account
  • 🔹 Can be used for authorization in corporate systems
  • 🔹 Allows you to track a device within one manufacturer (for example, Samsung KNOX)

The main difference from IMEI or MEID is the UDID is not tied to the communication module. It is needed for:

  • 📱 Developers: linking devices to test assemblies (Firebase App Distribution, TestFlight for Android)
  • 🏢 Corporate users: registration in MDM systems (MobileIron, VMware Workspace ONE)
  • 🔐 Security: device authentication in banking or government applications
  • 📊 Analysts: tracking unique installs (before restrictions were introduced on ANDROID_ID in Android 10)

Starting from Android 10 (API 29)Google has tightened its privacy policy. Now ANDROID_ID (which used to be often called UDID) is reset when all data is deleted (factory reset), and access to it is limited. Instead, they use:

Identifier Format Does it change after? reset? Does it require permission?
ANDROID_ID (Settings.Secure.ANDROID_ID) 64-digit hash Yes (with Android 10) No (but limited for third-party applications)
build.serial Custom string (for example, R58M23X1YZZ) No Yes (READ_PHONE_STATE)
Google Advertising ID (GAID) 32-digit hash Can be reset manually No (but the user can disable)
IMEI/MEID 15 digits No Yes (READ_PHONE_STATE)
⚠️ Attention: Starting from Android 12even build.serial can be hidden for applications without special permissions. If you need a UDID for a corporate system, check with the administrator which identifier is required - it may be required manual extraction via adb.
📊 Why did you need UDID on Android?
Installing a beta version of the application
Registration in the corporate system
Development/debugging Software
Other

UDID vs IMEI vs serial number: what is the difference

Many users confuse UDID with IMEI or serial number. Let's look at the key differences:

  • 📱 IMEI (International Mobile Equipment Identity) - unique number communication module (modem). Linked to SIM card and operator. You can find out through *#06#. Not suitable as UDID, because:
    • Absent on tablets without LTE
    • May change when replacing the motherboard
  • 🔢 Serial number (Serial) Number) —assigned by the manufacturer (for example, Samsung, XiaomiCan be found in the settings or on the box. Not always unique globally —some brands repeat numbers in different regions.
  • 🔑 UDID (in the broad sense) is any stable identifier that:
    • Does not depend on the SIM card
    • Does not reset when updating firmware
    • Can be used for software identification

In practice, “UDID” on Android often means:

  1. Settings.Secure.ANDROID_ID — before Android 10, this was the main “pseudo-UDID”. Now it changes after a reset.
  2. build.serial — serial number, available. via android.os.Build.SERIAL. On some devices (for example, Pixel) may be empty.
  3. Combination of ANDROID_ID + IMEI + MAC addresses (used in some MDM systems).

Example: if you need to register a device with Firebase for testing, the system may ask UDIDbut actually expect ANDROID_ID or hash from build.serial + IMEI.

💡

If the service asks for "UDID" but not clarifies the format - try sending ANDROID_ID (can be obtained through the app Device ID from the Play Market). In 70% of cases this is enough.

How to find out UDID on Android: 4 working methods

Depending on the version of Android and the presence of root access, there are several ways to get an identifier that can be used as a UDID.

Method 1: through the app (without root)

The simplest method is to use utilities from Google Play:

  1. Install the application Device ID (from EVOZI) or UDID (from Kosh).
  2. Open section Android ID or Unique Device ID.
  3. Copy value ANDROID_ID (64 characters) or Serial Number.

Example output: 

ANDROID_ID: 5a3b7e2d1f8c4096

Serial: R58M23X1YZZ


IMEI: 861234567890123

Method 2: Via ADB (without root)

If you have USB debugging i adb, do:

adb shell settings get secure android_id

To get the serial number:

adb shell getprop ro.serialno
⚠️ Attention: On devices with Android 11+ the command getprop ro.serialno can return an empty string if the manufacturer has blocked access. In this case, use adb shell cat /proc/cpuinfo and look for the string Serial.

Method 3: Through Engineering Mode (for devices on MTK)

On smartphones with a processor MediaTek (for example, Xiaomi Redmi, Realme):

  1. Dial in the phone application ##36446337##.
  2. Go to Connectivity → CDS Information → Radio Information.
  3. In the field AT+ enter AT +EGMR=1,7 and click SEND AT COMMAND.
  4. The response will contain a line with UDID or a similar identifier.

Method 4: Through root and system files

If you have root-access, the UDID can be retrieved from:

  • 📁 /data/data/com.android.providers.settings/databases/settings.db (field android_id)
  • 📁 /sys/class/net/wlan0/address (Wi-Fi MAC address, sometimes used as part of the UDID)
  • 📁 /proc/cpuinfo (string Serial)

Example command for extraction:

su

sqlite3 /data/data/com.android.providers.settings/databases/settings.db "SELECT value FROM secure WHERE name='android_id';"

☑️ Check before sending UDID

Done: 0 / 4

Why do developers need your device's UDID

If you have ever signed up for a beta app or accessed proprietary software, you have been asked to indicate UDIDWhy?

  • 🔒 Access control: UDID. is tied to the list of allowed devices in Apple Developer Portal (for iOS) or Firebase Console (for Android). This prevents leakage of beta versions.
  • 📦 Debugging: Logs from a device can be filtered by UDID to separate bugs from one user from another.
  • 📈 Analytics: In corporate applications, UDID is used to track device activity (for example, in IBM MaaS360).
  • 🛡️ Security: Banking applications (for example, SberBank Online) can check the UDID for substitution (if it suddenly changes, this may indicate hacking).

Practical example: the company Netflix previously used UDID to block rooted devices. Now they have switched to SafetyNet Attestationbut some services still rely on old methods.

Important: Starting with Android 10, applications cannot receive the ANDROID_ID of others. applications - only your own. This means that it is impossible to obtain a “universal” UDID in the classical sense on modern Android devices without special permissions.

Is it possible to fake the UDID?

Technically yes, but this requires root access and changing system files. For example, you can edit settings.db or. replace build.prop. However, such actions will trigger the operation Google Play Protect and may block access to banking applications.

Dangers and limitations of using UDID

Despite the convenience, working with UDID is associated with risks:

  1. Privacy: UDID can be used to track the user even after resetting the settings (if we are talking about build.serial). IN EU this contradicts GDPR.
  2. Blocks: Some services (for example, Pokémon GO) were banned. devices by UDID for cheating.
  3. Android restrictions:
    • C Android 10 ANDROID_ID resets when factory reset.
    • C Android 12 build.serial hidden for most applications.

UDID alternatives that modern applications use:

Method Use example Disadvantages
Google Advertising ID (GAID) Advertising networks (AdMob, Facebook Audience Network) The user can reset
Installation ID Applications like Telegram or WhatsApp Changes when reinstalled
SafetyNet Attestation Banking applications, Netflix Requires Internet and server verification
⚠️ Attention: If you are asked to provide a UDID to “unlock premium features” in an unknown application, this is a scam. Legitimate services (like Firebase or Xamarin) never request a UDID through third-party channels (for example, email or Telegram).

UDID on custom firmware and devices with root

On devices with custom ROM (for example, LineageOS, Pixel Experience) or root access, working with UDID has the following features:

  • 🔧 ANDROID_ID can be generated anew at each reboot if the firmware is compiled with errors.
  • 🔄 build.serial can be changed by editing /system/build.prop (line ro.serialno).
  • 🚫 Some MDM systems (for example, Hexnode) block devices with a changed UDID.

Example of change ro.serialno:

su

mount -o rw,remount /system


echo "ro.serialno=NEW_SERIAL_123" >> /system/build.prop


reboot

After such manipulations:

  • ✅ Applications like Magisk or LSPosed can mask the UDID to bypass checks.
  • ❌ Banking applications (for example, Tinkoff) will stop working due to the triggering of SafetyNet.
💡

On custom firmware, UDID may be unreliable. If you need a stable identifier for corporate systems, use official Android builds.

Common mistakes when working with UDID

Users and developers often encounter the following problems:

  1. Confuse UDID with IMEI:

    Example: send 861234567890123 (IMEI) instead 5a3b7e2d1f8c4096 (ANDROID_ID).

  2. Copy an incomplete identifier:

    ANDROID_ID Must be exactly 64 characters. If less, it means it was not completely copied.

  3. Does not take into account the Android version:

    On Android 9 and below ANDROID_ID does not change after the reset, but on Android 10+ it changes.

  4. They use incorrect tools:

    Some applications from the Play Market do not show ANDROID_ID, but the hash from IMEI + MAC, which may not be suitable for registration in Firebase.

How to avoid errors:

  • 📋 Always check with the recipient of the UDID which identifier is needed (ANDROID_ID, build.serial or a combination).
  • 🔍 Check the length of the copied code (for ANDROID_ID — 64 characters, for build.serial —usually 11-15).
  • 📱 If the UDID is not accepted, try getting it through adb instead of the application.

FAQ: Frequently asked questions about UDID on Android

Is it possible to find out the UDID of someone else's device remotely?

No. UDID (in any of its manifestations) can only be obtained from physical access to the device or through special software with administrator rights (for example, in corporate MDM systems, you can calculate it ANDROID_ID or build.serial impossible.

Why did my UDID change after resetting the settings?

Most likely, we are talking about ANDROID_IDStarting from Android 10, it is generated again. at factory reset. If you need a persistent identifier, use build.serial (but it requires permission READ_PHONE_STATE).

Is it possible to use UDID to track a device like GPS?

No. UDID is just a string that does not contain location information. However, if an attacker knows your UDID and has access to a database (for example, a corporate MDM system), he can link other data to it, including movement history (if it is logged).

How to reset or change UDID on Android?

It depends on the type of identifier:

  • ANDROID_ID: resets automatically when factory reset (Android 10+).
  • build.serial: can only be changed with root access (see section above).
  • Google Advertising ID: reset in settings (Settings → Google → Advertising → Reset advertising ID).

Why do some games (for example, Genshin Impact) request UDID?

Games use UDID (or its analogues) for:

  • Linking an account to a device (multi-account protection).
  • Detecting cheating applications (for example, GameGuardian).
  • Restricting access to regional versions (for example Honor of Kings in China).

If the game has blocked your device by UDID, contact support with proof of purchases - sometimes the blocking is removed.