This error occurs when you try to reinstall an android application that is signed with a different key than already installed application. This may occur if you are a developer and installed the signed version of the application to your device (from Google Play Store) and you want to install a debug version of the same application for development purposes. To prevent this you may sign your development/debug versions with the same key that you use for publishing your application to Google Play Store. To do this you have to change your debug certificate with your real certificate. Debug certificate used is stored in the .android/debug.keystore file in your home directory. You have two options:

    Export your release key from your release keystore and import it to debug.keystore Copy your release keystore over your debug.keystore and change store and key passwords to “android

I will describe steps for second option.

    Copy your real keystore (release keystore) over ./android/debug.keystore file Change keystore password to android using keytool:

             keytool –storepasswd –new android –keystore debug.keystore

    Use keytool to list keyaliases:

             keytool –list –keystore debug.keystore

    Above command will list key aliases and their corresponding certificate fingerprints. Find your key alias you have used to sign your application for Google Play Store

    Now change password of the key you have used to sign your application for Google Play Store to android:

             keytool –keypasswd –alias your_key_alias –new android –keystore debug.keystore

    Now rename your key alias (your_key_alias on above command) to androiddebugkey:

             keytool –changealias –alias your_key_alias –keystore debug.keystore

   Above command will ask you destination alias name, enter androiddebugkey. It will also ask your store password like all above commands.

After that your debug versions can be installed over the version downloaded from Google Play Store.