DAT File
Did your computer fail to open a DAT file? We explain what they are used for and recommend software that we know can open or otherwise handle your .DAT files.
What is a DAT file?
A .DAT file is an Outlook Email in Rich Text Format (winmail.dat) file. Sometimes you may receive an email attachment named winmail.dat and wonder what that is. You see it because the sender of the message used the Microsoft Outlook email client and sent the email in Rich Text Format, a format that allows different font sizes and colors.
Not all email clients understand this format, and in this case, the Rich Text formatted email message ends up as a winmail.dat file attached to the email.
Technically these files are called TNEF files, short for Transport Neutral Encapsulation Format, which is the name Microsoft used for the file format.
There are various stand-alone viewers available if your email client does not support winmail.dat files.
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How to open DAT files
You will need a program compatible with the specific file you are trying to open, as different programs may use files with extension DAT for different purposes. We have identified 1 DAT opener for Windows that is compatible with this specific type of DAT file.
Programs that open DAT files
 | Free File Viewer | Verified |
What else are .DAT files used for?
While Outlook Email in Rich Text Format (winmail.dat) is a popular type of DAT-file, we know of 28 different uses of the .DAT extension.
The DAT file extension indicates to your device which app can open the file. However, different apps may use the same file extension for different types of data. So a DAT opener may not be able to open all kinds of DAT files. In this case, look through all formats to make sure you find the best suited DAT viewer.
- Adobe Freehand Project
- Allegro Game Engine data
- Bitcoin data
- CardFile PIM data
- CHEMICAL Molecule Data
- Clarion 2 Database
- Clrmamepro DAT / MAME Listinfo ROM info
- DirTel Database
- DVD Master Disc Control File
- EasyRecovery saved recovery state
- GeoLite1 IP geolocation database
- InnoSetup Uninstall Log
- LabVIEW Binary Data Log
- Linux kernel x86 bootable
- LocoScript Data
- Microsoft Internet Explorer cache
- MicroStation Resource data
- MirandaIM database
- Novell Librarian Data
- Outlook Email in Rich Text Format (winmail.dat)
- Palm Desktop DateBook
- PasswordBox Encrypted Database
- Runtime Software compressed disk image
- StarForce protected data
- Surface-water Modeling System Dataset
- VideoCD MPEG
- Windows boot log data
- Windows Registry Hive
Windows Registry Hive
Microsoft Windows uses a concept called the Windows Registry to store various configuration settings that affect how Windows and installed software works. The registry values are stored in different registry files, called Registry Hives. For example, the Registry holds information about which application you have selected to be the default opener for JPEG images.
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Bitcoin data
The original Bitcoin client stores private key information in a file named wallet.dat. This file contains your private keys, public keys, the transactions related to your wallet, and other important data. If you have an HD wallet, it also includes the HD seed and the private key's derivation paths. Keep this file safe, as it contains your bitcoins.
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LabVIEW Binary Data Log
LabVIEW provides an easy-to-use application development environment designed specifically for the needs of engineers and scientists. Without any prior programming experience, you can use LabVIEW to take measurements from various devices and create custom software functionality.
Data captured by your application can be logged to files in various formats using built-in functions. The DAT format is more compact than a user-readable text format and can contain various data, e.g., temperature readings.
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DAT opener for Windows 10
 | LabVIEW | Verified |
Surface-water Modeling System Dataset
Surface-water Modeling System (SMS) Software is a solution for building and simulating surface water models. It is a graphical user interface and analysis tool that allows engineers and scientists to visualize, manipulate, analyze, and understand data. Build a conceptual model in SMS by constructing a high-level representation of the model using familiar GIS objects: points, arcs, and polygons. The data file contains these objects.
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Various DAT file openers, viewers, etc.
 | SMS | Verified |
MicroStation Resource data
MicroStation is a Computer-Aided Design (CAD) software used in the architectural and engineering industries to design structures and products in 2D and 3D. A resource is an element that can be used in such a drawing project.
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Various DAT file openers, viewers, etc.
 | MicroStation | Verified |
Clarion 2 Database
This file contains the data users have entered into a program developed in the Clarion programming language. Clarion is a development environment focused on creating database applications. Therefore, the database file is not used by Clarion itself, but one of the hundreds of programs developed using this programming language. Some viewers can display the content of any Clarion generated database, as the database format itself is standardized.
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Runtime Software compressed disk image
DriveImage from Runtime Software is used to create copies of an entire hard drive partition. A drive copy is saved as an XML file accompanied by a DAT file, and optionally a series of files named 001, 002, 003, etc., if you have selected to split the copy into multiple files of smaller size.
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Various DAT file openers, viewers, etc.
 | DriveImage XML | Verified |
CHEMICAL Molecule Data
CHEMICAL is a molecular modeling program for MS-DOS by Larry Puhl that bonds and places atoms that the user has selected from a Periodic Table. Its associated data files contain molecular data models.
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Adobe Freehand Project
Freehand was a vector drawing program for Windows and Mac from Adobe, which acquired it from Macromedia. At the time, it was a market leader in vector drawing programs. The DAT file created by this program was a vector drawing project file.
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Allegro Game Engine data
Data file for games developed using the Allegro Game Engine. The files can contain graphics and sound elements.
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Clrmamepro DAT / MAME Listinfo ROM info
This type of dat file contains information about an arcade machine ROM copy. The files contain, e.g., name of the game, manufacturer, size, checksums etc. The checksums can be used to verify that your copy of the ROM is complete and unaltered.
MAME is a Multi Arcade Machine Emulator that can run old arcade games on your computer.
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Various DAT file openers, viewers, etc.
 | MAME | Verified |
 | clrmamepro | Verified |
DirTel Database
DirTel is an address book for MS-DOS, and the associated DAT file contains the addresses entered by the user.
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PasswordBox Encrypted Database
PasswordBox is a console-mode program that will keep all your passwords safe in an encrypted database protected by a master password. The database consists of a single .dat file.
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Various DAT file openers, viewers, etc.
| PasswordBox | Verified |
DVD Master Disc Control File
DDVID.DAT is one of several control files written to the area reserved for mastering content on a Master DVD to prepare pressing duplicates.
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GeoLite1 IP geolocation database
GeoLocation database from Maxmind. It contains mappings between IP-addresses and physical locations, so you can use a user's IP address to look up the user's country. Home pages often use it to enable specific behavior when a website visitor is from a specific country - e.g. block access, change language, or change currency.
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InnoSetup Uninstall Log
InnoSetup is a Windows installation program used by developers to create installation packages of their software. The uninstall log files contain information about which files must be removed if you decide to uninstall a software program.
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CardFile PIM data
Data file for the legacy Personal Information Manager software, CardFile PIM, for the Atari home computers.
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EasyRecovery saved recovery state
EasyRecovery from OnTrack is a software tool to recover data from crashed hard drives and solid-state disks. During the recovery process, it saves a state file so it knows which sections of the drive have been processed so far.
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Various DAT file openers, viewers, etc.
 | Ontrack EasyRecovery | Verified |
Linux kernel x86 bootable
A Linux kernel is the "brain" of a Linux system. It is the main Linux operating system file that provides the low-level functions of the operating system.
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LocoScript Data
LocoScript was a word processor first developed for the Amstrad CPC 464 home computer in the late 1980s. Later, versions were made for MS-DOS. Documents saved by LocoScript used the .dat file extension.
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Microsoft Internet Explorer cache
The Internet Explorer web browser stores certain data on your PC to speed up the display of web pages. For example, if you revisit the same page, the web browser will only need to download the changed content and not, e.g., fonts and images that have not changed. This saves both bandwidth and time.
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MirandaIM database
Miranda IM was an instant messenger application for Windows with support for multiple messaging protocols. You could chat on ICQ, IRC, AOL, and many other platforms using this single application.
The database file contains the log/history of all your chats.
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Various DAT file openers, viewers, etc.
| Miranda IM | Verified |
Novell Librarian Data
Through our analysis of DAT files, we know that one use of the format is Novell Librarian Data. We have not yet described in detail what these files contain and what they are used for, but our team is working tiredlessly through thousands of file formats. We'd love hearing from you if you have information about the format.
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Palm Desktop DateBook
Calendar database file used by Palm desktop software, a companion software for Palm Pilot handheld devices. This file contains a user's calendar entries and repeating events.
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Various DAT file openers, viewers, etc.
 | Palm Desktop | Verified |
StarForce protected data
StarForce is a copy protection system. It stores one or more files in a single "container" that gets protected by their proprietary system. Software developers embed part of the StarForce protection into their application, enabling it to read the data from the protected container file if the user has entered the correct license key. Without the key, the protected data cannot be read.
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VideoCD MPEG
MPEG encoded video stream in a RIFF container used in VideoCDs.
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Various DAT file openers, viewers, etc.
 | Final Media Player | Verified |
Windows boot log data
When a Windows PC starts (boots), Windows will log data about the boot process to a log file. This file will help resolve startup problems as the administrator will be able to see how far in the startup process Windows came before a problem occurred.
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Not sure exactly what type of file you are trying to open? Try our new File Analyzer. It is a free tool that can identify more than 11,000 different kinds of files - most likely yours too! It will help you find software that can handle your specific type of file. Download File Analyzer here.