Reason is i have an apk which works as an installer. When the user installs and opens it, it prompts the user to install another apk (drm free) which was inside the installer apk. However, after signing and zipaligning both with APK Signer tool and Private keys i get this error when installing: an existing package by the same name with a conflicting signature is already installed basically, both the apk (installer) and apk (theme) have the same package name. When the apk (theme) is installed, it should overwrite the apk (installer). Any help on this would be greatly appreciated. I think both the installer apk and theme apk should have the same certificates in order to overwrite each other, but i don't know how.