There is only one file type that uses the .XAPK extension:
Compressed Android Package File
An XAPK file is a package used to install Android apps on mobile devices. It is similar to the standard .APK format, but may contain other assets used by the app, such as an .OBB file, which stores graphics, media files, and other app data. XAPK files are used for distributing apps on third-party Android app download websites. They are not supported by Google Play.
Because XAPK files are not standard app installer packages, they must be installed manually or installed using an XAPK installer. After downloading an XAPK file, you can install the app (the APK file stored in the package) to an Android device using XAPK Installer. If you would like to manually install the additional files, you can unzip the XAPK file (which is a standard .ZIP file) and place the extracted files in the appropriate location on your device.
A drawback to delivering apps via Google Play is that the size of the APK file must be 50MB or smaller, which forces app developers to use other files (such as OBB files) to store additional graphics and media assets. Because of this limitation, some developers make their apps available from sites other than Google Play. The XAPK format was introduced to package the APK file and OBB file together for a seamless delivery and installation process when downloading an Android app from a non-Google Play site.
XAPK files are typically legitimate Android packages, but they can also be used to distribute and execute malware attacks. Do not install an XAPK file unless you trust the file's source.
Updated: May 7, 2021