ADB device unauthorized error: how to fix on Windows, Linux, macOS

What the device unauthorized Error Means

The device unauthorized error in Android Debug Bridge (ADB) means that the computer is not authorized to debug the connected Android device. The full output of the adb devices command looks like this:

List of devices attached
0123456789ABCDEF    device unauthorized

This error appeared starting with Android 4.2 (API 17), when Google introduced an explicit confirmation mechanism for USB debugging. Without authorization, ADB cannot execute commands (app installation, log access, file operations, etc.).

Common Causes

1. Authorization request not confirmed — the "Allow USB debugging?" dialog on the device screen was not accepted by tapping "OK."
2. "USB debugging" option disabled — debugging is not activated in the developer options.
3. Another computer already authorized — a different computer's key is stored on the device, so the prompt does not appear.
4. Outdated or incorrect drivers (Windows) — the system does not recognize the device correctly.
5. Corrupted ADB authorization data — the key files on the device or computer are damaged.
6. Incompatible cable or port — the cable is charge-only (does not support data transfer), or the USB port is faulty.

Method 1: Confirm Authorization on the Device

The most common and straightforward solution is to confirm the prompt on the phone's screen.

1. Ensure USB debugging is enabled:
   Settings → Developer options → USB debugging (the checkbox should be active).
   If "Developer options" is not visible, enable it: Settings → About phone → Build number (tap 7 times).
2. Connect the device to the computer via a USB cable (an original, data-capable cable is recommended).
3. A dialog will appear on the Android screen:
   "Allow USB debugging?"
   Check the box "Always allow from this computer" and tap OK.
4. Check the status:

   adb devices
   

   In the output, the device's serial number should be prefixed with device instead of unauthorized.

⚠️ Important: If the window does not appear, try unplugging and reconnecting the cable, rebooting the device, or changing the USB mode (e.g., to "File Transfer").

Method 2: Restart the ADB Server

Sometimes restarting the ADB service helps.

1. Open a terminal (Command Prompt, PowerShell, bash).
2. Run:

   adb kill-server
   adb start-server
   

3. Reconnect the device and check:

   adb devices
   

Method 3: Reset ADB Authorizations on the Device

If the authorization prompt does not appear, or you want to start "from scratch":

1. On the device, go to:
   Settings → Developer options → USB debugging → Revoke USB debugging authorizations.
2. Confirm the action.
3. Disconnect and reconnect the USB cable.
4. Confirm the authorization prompt (as in Method 1).

Method 4: Update or Reinstall Drivers (Windows)

On Windows, driver issues are a frequent cause.

1. Open Device Manager (Win + R → devmgmt.msc).
2. Find your device (usually under "Portable Devices" or "Other devices" with a yellow exclamation mark). The name may be Android or ADB Interface.
3. Right-click → "Update driver" → "Search automatically for updated driver software".
   Or manually: download the driver from the manufacturer's website (Samsung, Xiaomi, etc.) or use the Google USB Driver (for Nexus/Pixel) via SDK Manager.
4. After installation, reconnect the device and check adb devices.

💡 Tip: For a universal solution, install Universal ADB Driver or Minimal ADB and Fastboot — these often resolve authorization issues.

Method 5: Check Cable and USB Mode

1. Use a high-quality cable that supports data transfer (not just charging). Try a different cable or a different USB port on the computer.
2. On the device, in the notification panel when USB is connected, select the "File Transfer" (MTP) or "PTP" mode, not "Charging only."
3. If there is an option for "USB debugging (Security settings)", try disabling it.

Method 6: Manually Add the Authorization Key (Advanced)

If nothing else works, you can manually copy the authorization key.

1. On the computer, locate the adbkey.pub file (typically in ~/.android/ on Linux/macOS or C:\Users\<Username>\.android\ on Windows).
2. On the device (root access required), copy the contents of this file to /data/misc/adb/adb_keys (reboot the device after).
3. Without root, this method will not work — it's better to reset authorizations (Method 3).

Prevention

• Always confirm authorization when connecting a device to a new computer for the first time.
• Use the same cable and USB port consistently for debugging.
• Update ADB to the latest version via SDK Manager or a standalone package.
• Do not disable USB debugging after setup — leave it enabled if you frequently use ADB.
• On Windows, install universal ADB drivers once to avoid issues with different devices.

Frequently Asked Questions

What if the device doesn't appear in adb devices at all?

First, check if the system sees the device (in Device Manager or via lsusb on Linux). Ensure USB debugging is enabled and the correct USB mode is selected (not "charge only"). Try a different cable or port.

Can I authorize a device without a screen (e.g., broken display)?

Yes, but root access is required. You can manually add the computer's key to /data/misc/adb/adb_keys (see Method 6). Without root, authorization is impossible.

Why does the error return after confirming authorization?

You might have selected "Deny" or not checked "Always allow." Also, check if developer settings reset after a reboot (rare, but possible). Try revoking authorizations (Method 3) and confirm again.

Does this work on Android 12 and higher?

Yes, the authorization mechanism remains. On newer versions, an additional prompt may appear asking you to trust the computer with an RSA fingerprint — this also needs to be confirmed.