How to Fix "ADB Unauthorized" Error on Windows

Your device shows up in adb devices — that is progress. But instead of a clean device status, you see unauthorized. This is a different problem from a device not being detected at all, and it has a specific set of causes centered around ADB's RSA key authorization system.

This article covers every reason an Android device can end up in the unauthorized state and how to resolve each one definitively. If your device is not showing up at all (not even as unauthorized), see our guide on fixing the ADB device not found error instead.

How ADB Authorization Works

When ADB connects to an Android device for the first time, it performs an RSA key exchange. Your computer has an ADB key pair stored locally — a private key at %USERPROFILE%\.android\adbkey and a public key at %USERPROFILE%\.android\adbkey.pub. ADB sends the public key to the device, and the device asks the user to approve it via a dialog on-screen.

Once you approve, the device stores that public key in its own list of trusted keys. Every subsequent connection from the same computer is silently authorized. The "unauthorized" error means this handshake has either not happened yet, was rejected, or the stored keys have become invalid.

Fix 1: Accept the Authorization Dialog on Your Device

This is the most common cause. The authorization dialog appears on your phone screen when ADB first tries to connect, but it is easy to miss — especially if your screen is locked or times out quickly.

1. Make sure your phone screen is unlocked and active.
2. Disconnect the USB cable, then reconnect it.
3. Watch your phone screen immediately. Within a few seconds you should see a dialog: "Allow USB debugging?" showing the RSA key fingerprint of your computer.
4. Tap Allow. If you want this computer to always be trusted automatically, check "Always allow from this computer" first.
5. Run adb devices on your PC — the device should now show as device.

If the dialog does not appear after reconnecting, try running adb devices from the command line immediately after connecting — this sometimes triggers the prompt to appear on the device.

Fix 2: Revoke USB Debugging Authorizations

If the authorization dialog appeared but the device is still showing as unauthorized (or the dialog never appears on reconnect), the stored keys may be corrupted or mismatched. Revoking all stored authorizations on the device forces a fresh key exchange.

1. On your Android device, go to Settings > System > Developer Options.
2. Scroll down and tap "Revoke USB debugging authorizations".
3. Confirm the action — this clears all trusted computer keys from the device.
4. Disconnect the USB cable.
5. On your PC, restart the ADB server:
   

   adb kill-server
   adb start-server

6. Reconnect the USB cable with your phone screen unlocked.
7. Accept the authorization dialog when it appears.

Fix 3: Delete the ADB Key Files on Windows

If the device still shows as unauthorized after revoking authorizations on the phone, the problem may be on the Windows side — specifically, a corrupted or invalid adbkey file. Deleting the key files forces ADB to generate a fresh key pair.

The ADB key files on Windows are located at:

%USERPROFILE%\.android\adbkey
%USERPROFILE%\.android\adbkey.pub

On most systems this resolves to something like C:\Users\YourName\.android\adbkey. To delete them:

1. Press Win + R, type %USERPROFILE%\.android, and press Enter. This opens the .android folder in File Explorer.
2. Delete both adbkey and adbkey.pub.
3. Open a command prompt and run:

   adb kill-server
   adb start-server

4. ADB will generate a new key pair automatically when it starts.
5. Reconnect your phone with the screen unlocked and accept the new authorization dialog.

Important: Deleting the key pair means all devices that previously trusted this computer will need to re-authorize. If you have multiple devices set up, be prepared to accept the dialog on each one again.

Fix 4: Restart the ADB Server

Sometimes the ADB server process gets into a state where it consistently fails the authorization handshake even with valid keys. A clean server restart can resolve this without any changes to key files:

adb kill-server && adb start-server

Then disconnect and reconnect your device. If a dialog appears on your phone, accept it. Run adb devices to verify the result.

Fix 5: Check for Multiple ADB Versions

If you have multiple copies of ADB installed — for example, one from Android Studio, one from a standalone platform-tools download, and one from a third-party Android app — they may be using different key files or different server instances. This can cause persistent authorization failures that seem inexplicable.

To find all ADB executables on your system:

where adb

If this returns more than one path, you need to consolidate. Keep only the version you want (preferably the latest from Google's platform-tools), remove the others from your PATH, and do a clean adb kill-server && adb start-server cycle.

Verifying the Fix

After any of the fixes above, run adb devices and confirm the output looks like this:

adb devices
# Expected output:
# List of devices attached
# R3CX90BXXXX    device

The word device (not unauthorized, not offline) confirms the authorization was successful. You can then run a shell command to double-check end-to-end connectivity:

adb shell getprop ro.product.model

This should print your phone's model name without any errors.

Conclusion

The ADB unauthorized error is almost always resolved by one of four approaches: accepting the authorization dialog on your phone, revoking and re-doing USB debugging authorizations on the device, deleting and regenerating the ADB key files on Windows, or restarting the ADB server. Work through them in that order and you should be connected within minutes.

For a less friction-heavy experience overall, Andora wraps all of this ADB complexity into a clean Windows application where device management just works — no terminal required.