ADB Android Device Unauthorized

It's likely that the device is no longer authorized on ADB for whatever reason.

1. Check if authorized:

<ANDROID_SDK_HOME>\platform-tools>adb devices
List of devices attached
4df798d76f98cf6d        unauthorized

2. Revoke USB Debugging on phone

If the device is shown as unauthorized, go to the developer options on the phone and click "Revoke USB debugging authorization" (tested with JellyBean & Samsung GalaxyIII).

3. Restart ADB Server:

Then restarted adb server

adb kill-server
adb start-server

4. Reconnect the device

The device will ask if you are agree to connect the computer id. You need to confirm it.

5. Now Check the device

It is now authorized!

adb devices
<ANDROID_SDK_HOME>\platform-tools>adb devices
List of devices attached
4df798d76f98cf6d        device

Try forcing ADB to create new keys.

• On Linux/OSX:

    $ mv ~/.android/adbkey ~/.android/adbkey.old
    $ mv ~/.android/adbkey.pub ~/.android/adbkey.pub.old
    $ adb kill-server
    $ adb start-server
  

• On Windows 10 (thank you, Pau Coma Ramirez, Naveen and d4c0d312!):

  • Go to %HOMEPATH%\Android\.android\
  • Look for files called adbkey or adbkey.pub.
  • Delete these files. Or, if you want to be on the safe side, move them to another directory.
  • Repeat the above steps in %USERPROFILE%\.android\
  • Try again

After this I didn't even need to unplug my phone: the authorization prompt was already there. Good luck!

Ohhh finally I figured it out! After removing Eclipse directory I installed it into another directory.

echo %ANDROID_SDK_HOME%

has displayed wrong path to sdk directory.

1. set ANDROID_SDK_HOME "E:\adt-bundle-windows-x86_64-20140321\sdk"
2. unplug device
3. adb kill-server
4. adb start-server
5. plug device

After these steps, I was able to see confirmation dialog with RSA fingerprint on my phone :)