The DAT file format has three common applications: firstly as a general data file, secondly as the Winmail.DAT file used in email, and finally for VCD video files. DAT files are used to reference data files, which are normally comma delimited and contain data in ASCII format.

File Extension DAT is opened and viewed using various programs including Microsoft Notepad and Microsoft Word. As such the DAT file association often identifies a generic data file that can be created by various applications and viewed using a text editor.

However, in certain circumstances the DAT file can only be opened or accessed by its creator application. In these cases the DAT file may hold data in a binary or text format. Some of the applications that open create and reference DAT files include Corel WordPerfect, Microsoft Visual Studio, Nullsoft Winamp, Nero Showtime, Ontrack EasyRecovery, SoftVelocity Clarion, MapInfo and Runtime GetDataBack. To open DAT files on Windows and Mac operating systems, users are required to install the original program used to create the file. Conversely, they may use a text editor, if the file is a text based DAT file.

The Winmail.DAT email attachment instance of the DAT file association is categorized as a Misc. file. Winmail.DAT files hold format information for Rich Text File messages normally sent from the Microsoft Exchange Server. The files are then added to the email in case the recipient’s e-mail client is not able to support Rich Text Format. The Winmail.DAT file is not useful to users that do not make use of the Exchange server to retrieve email messages. To open DAT files on a Windows operating system, users are required to install WMDecode, WinMail Decoder Pro, Microsoft Outlook and Microsoft Mail.

The VCD instance of file extension DAT, which is the third category of DAT format, is a video file used to stream video from Video CDs (VCDs) that are normally saved in the MPEG-2 or in MPRG-1 formats containing video data. It is also important that users note that the DAT instance for video CDs can be opened on CD player applications and that the user does not need to open the file manually. To open the DAT instance of the VCD file category, Mac and Linux users require the VCDGear application. For Windows users, they require to install VCDGear, River Past Video Cleaner and CyberLink PowerDirector applications.