Open STG File
A file with the STG extension is a backup created by ActiveSync, a program used to synchronize PCs with mobile devices.
ActiveSync, from concept
ActiveSync is an application and protocol developed by Microsoft and used to synchronize data between mobile devices and desktop computers based on Windows systems.
Some Groupware type servers are compatible with ActiveSync and can be used to exchange information on mobile devices.
ActiveSync provides a way for Microsoft Windows users to move documents, emails, tasks, contact lists, calendars, bookmarks, and files between the PC and any mobile device.
It also supports manual file transfer to mobile devices, along with limited backup functions and the ability to install or uninstall mobile apps from the mobile device.
Some devices are supported, such as PDAs and smartphones running Windows Mobile, Windows CE or BlackBerry 10 as the operating system.
However, ActiveSync does not support iPhone, older versions of BlackBerry, Palm OS, or Symbian.
Starting with Windows Vista, the ActiveSync application was replaced by Windows Mobile Device Center, but the underlying protocol is still called ActiveSync.
It is also important to note that Windows Phone 7 does not support ActiveSync synchronization.
Relationship between an STG file and ActiveSync
The STG file contains a backup of all files on the mobile device, including contacts, notes, and calendar data.
This turns the STG file into a container, and it usually appears with the filename backup.stg.
As relevant information, Microsoft removed the backup and restore function starting with version 4.2 of ActiveSync.
To recover backed up files with ActiveSync, use version 4 or earlier that supports STG files.
STG files, being Backup files, are a proprietary format that should not attempt to be manually opened by the user.