Winmail.dat files contain formatting information for Rich Text (RTF) messages sent from Microsoft Exchange Server; they are added to the end of e-mails when a recipient's e-mail client does not support RTF messages; the Winmail.dat file is not useful to users that do not use Outlook or Exchange Server to retrieve their mail.

Read more about Winmail.dat files, including how to open them and how to prevent them from being sent.

File created by Inno Setup, a program used for making Windows program installers and uninstallers; typically named unins000.dat (or a similar name) and is located in the program installation directory; contains data that helps Inno Setup uninstall the program when the user chooses to do so from the Windows Control Panel.

Inno Setup ".dat" file has a corresponding .EXE file named unins000.exe (or a similar name). When the executable is run, it uses the information in unins000.dat to uninstall the program from the Windows computer.

A DAT file is a data file used by Minecraft, a 3D exploration and construction game. It is saved in a compressed Gzip format and may save various kinds of data, including player inventory, player position, and world information. DAT files are used for saving world state information as well as for tracking player progress.

DAT files were also used for storing level "chunks," which are small map pieces that are loaded on demand as a player navigates through the world. This format was introduced beginning with the Minecraft Infdev version, and the chunks used a 16 x 16 x 128 map dimension. Beginning with the Minecraft version 1.3 beta release, a new format called "Region" was introduced, which stores chunks with the .MCR extension. Subsequently, the .MCA format, called "Anvil," was introduced with patch 1.2.1. Minecraft DAT files have used different formats over incremental releases of the game. Therefore, one DAT file from one version of the game may not be compatible with another version. NOTE: Minecraft is a first-person perspective game where players construct and destroy blocks and avoid monsters in a 3D environment. Minecraft server is a Java program that runs as a command-line interface.

Application form data file created by the U.S. Online Nonimmigrant Visa Application (DS-160) process, which is made available from the U.S. Department of State's Consular Electronic Application Center; created by the online, browser-based application and contains data such as personal background information; used for saving and loading the application through the online form filing process.

A DAT file is a data file used by Piriform applications, such as CCleaner, Speccy, Defraggler, and Recuva. It acts as a flag, telling a Piriform application to operate in portable mode, which is used when users want to run a Piriform application from a USB drive, or when users do not want to leave traces on a computer system.

To run a Piriform application in portable mode, create a blank file named piriform.dat and save it to the application's installation directory. For example, for CCleaner, the file can be saved to C:\Program Files\CCleaner\. After the file is saved, CCleaner will store program settings in a file named CCleaner.ini, rather than using other storage locations, such as the Windows registry. NOTE: The contents of the piriform.dat file do not matter. Therefore, an empty file or a non-empty file that contains data will produce the same result.

Key file used by Piriform applications, such as CCleaner and Recuva, that help users manage their PCs; contains the registry key number that is referenced by the application in order to operate in the appropriate mode.

NOTE: If the file is moved or deleted from its location in the application directory, the application will operate in the trial mode instead of the purchased mode.

System save file used by Porteus, a portable Linux operating system (OS); contains saved changes that have been made to the Porteus OS; includes changes to system settings, bookmarks, downloaded files, and browser history.

The DAT file is used as a container that holds alterations you have made to Porteus, which enables you to keep your OS the same when installing it to other devices. It is a necessary container file if you are installing Porteus to devices formatted with a Windows file system. The file is used to retain data, such as symlinks, and Linux permissions, to run your system properly. To create a DAT file container to save your customizations, boot Porteus into the KDE, Xfce, or LXDE desktop interfaces. After the boot is complete, open the menu and select System → Porteus save.dat manager. Then follow the prompts to finish creating your DAT file.

Game package file used by SimCity 4, a city building simulation game; may contain several types of game data files, including .SC4MODEL, .SC4LOT, and .SC4DESC files; used for packaging files into usable content for the game.

SimCity 4 DAT files can be browsed using iLives Reader or DatGen (developed by DarkMatter).

Video stream from a Video CD (VCD) disc; typically saved in MPEG-1 or MPEG-2 format; contains the actual video data that is played from the VCD.

NOTE: Video CD players should play the video from the DAT files without having to open the files manually.

File used by the Microsoft Windows registry component; contains data for the system or user-level registry, such as passwords, account settings, or file associations; can be loaded into specific parts of the registry when a user logs into Windows.

A common registry hive file is NTUSER.DAT, which stores the user-level registry information. It is located in the C:\Users\[user]\ directory. Another common DAT file is SCHEMA.DAT, which is a registry backup and restore file that is located in the C:\Windows\System32\SMI\Store\Machine\ directory.