The .dat file extension is a generic extension used by different applications to save their specific data. DAT simply stands for data; as in the beginning, most of the operating systems allowed only 3-letter file extensions. There is no specific definition for DAT files that could be applied to all of them. And there is no single program responsible for creating or reading each type of DAT file.
DAT files are most of the time hidden in the application folder that generated them and you won’t notice they exist. Occasionally you might receive an email with a DAT attachment or a video in this format.
As DAT is not a regulated or well-specified file format, you might need to do some search and try different things to view or open them. As a counter-example, a file with the extension .docx is for sure a Word document, and a file with the extension .mp4 is a video file. For DAT files this rule doesn’t apply.
How to open a DAT file
Before looking for the right application to open the .dat file, it is important to know where did you get the file from and what was its intent.
The most common use case for .dat files:
- Winmail.dat file or ATT0001.dat received as an email attachment
- Video files
- Any other data in a proprietary or specific format that is not easily readable by humans
Additionally, if the file is in a folder below an application folder (usually c:\Program Files\<some app> or C:\Users\<username>\AppData\<some app>), it is probably an internal file used by this application and not meant to be open by any program.
How to open a .dat file received as an email attachment
If you received a .dat file as an email attachment with names winmail.dat or ATT0001.dat this is for sure a TNEF attachment. These special types of attachments are sent by Microsoft applications like Outlook or Exchange. Basically, these applications when not correctly configured will wrap all the e-mail content inside of one single attachment.
To open a winmail.dat file you can use the free online Winmail.dat Reader. The interface is very intuitive and all you have to do is upload the attachment file. If you need more directions, you can read our article explaining in detail how to open a winmail.dat file online.
How to open a video .dat file
Some video applications will like VCDGear and PowerDirector will save their video files as .dat files. To open these files you can use the application that generated them.
If you are certain it is a video file and you don’t possess any of the above mention video applications, you can download the free and open-source VLC video player and try opening the file with. If it is a video file, it will manage to open and decode it.
Opening .dat files with a text editor
If you are unsure of the file content, you can try opening it with a text editor. Not all .dat files can be opened as text and you might some garbage code that can only be read by a software application. But if you are lucky, you would be able to see and read its contents partially or fully.
Every operating system comes with a text editor like Notepad on Windows or TextEdit on mac. You can try to open the file in any of them. If the contents are not readable you can still try to scroll down the file. Some computer files mix binary and text code, and you might be able to read part of its contents.
If you need a more sophisticated text editor, we recommend the free Notepad++ as an alternative to the native text editors mentioned above.
Other types of .dat files
Here we provide a list of other know file types with the extension .dat. We wish you all the luck opening these files. If you have any comments or suggestions for this article, please don’t hesitate to contact us.
| File type | Common names | Application that opens it | Purpose |
|---|---|---|---|
| Minecraft Data File | level.dat | Mojang Minecraft, INVedit (windows only) | May save various kinds of data, like player inventory, player position, or world information. |
| Piriform Applications DAT File | portable.dat | CCleaner | Contains a Piriform license key or tells a Piriform application to operate in portable mode. |
| Inno Setup Uninstaller | unins000.dat | Application unistaller create by Inno Setup | Contains information on how to uninstall an application |
| Windows Registry Hive File | NTUSER.DAT | Windows | Windows Registry database file (don’t mess with it or your Windows might become unpredictable!) |
| Porteus Save Container File | porteussave.dat | Porteus | Saves changes done to the Porteus portable Linux system |
| Nonimmigrant Visa Application | U.S. Nonimmigrant Visa Application | Used as a file persistence for the online visa application | |
| GameMaker Studio Data Package | UndertaleModTool | GameMaker Studio audio package file |