Whether you can open a DAT file without the originating program depends on its content. If your DAT file was supposed to be a Microsoft Word document or another text-based document, it's easy to open it, and we'll show you how. If it was a different type of file, our method might still help you figure out what it was.

What Is a DAT File?

A DAT file is a generic file type that contains data in text or binary format.

Examples of DAT files in a Windows 10 folder.

You'll typically find them as "winmail.dat" files in email attachments created by Microsoft Exchange Servers. However, many other programs can create DAT files, too, usually storing information as a reference to a specific operation.

When you find a DAT file that's not stored with other files from a specific program, for example, driver files (file type: DLL), or if the name doesn't reveal the DAT file's origin, then it's difficult to tell whether you're dealing with text, pictures, movies, or something completely different. Without context, your DAT file could be anything.

How Can I Open a DAT File in Windows?

Giving advice on how to open a DAT file of an unknown source is difficult because there are so many options, depending on the original source of the file.

But say you were supposed to receive a Word document and what you did receive was a document with a DAT file extension. Basically, you have two straightforward options to open that file.

Option 1: Change the File Extension

First, you could try to change the file extension. If you don't see file extensions in Windows, go to the folder that contains your DAT file. In File Explorer, switch to the View tab, and click Options.

Within the Folder Options window, switch to the View tab once more and uncheck the option Hide extensions for known file types.

Windows 10 Folder Options with "Hide extensions for known file types" highlighted.

Now you can go back to your file and change the file extension from .dat to .doc, then open the file using Microsoft Word.

Option 2: Open the File

If you think it's a text-based document, you could simply try to open the DAT file with Microsoft Word, Notepad, or any other program you suspect created the original file.

To do this, right-click the DAT file, select Open with from the menu, then choose an application from the list. You can click More apps to show other programs than the ones suggested.

Windows 10 Open File With Menu with Notepad option highlighted.

If you wanted to associate DAT files with this program (not recommended), you could check Always use this app to open .dat files.

Both of the options above could leave you with a file that's full of gibberish, usually because you opened it in the wrong program. However, you may be able to gather what kind of file it really was.

For example, if you opened a DAT file that originally was a video file in Notepad, you might find a hint that it's actually an MP4. Try opening the file in a suitable program and see whether that gives you a better result.

Here are resources to open the most common types of DAT files:

You have to find the specific program that created the file to open it for many other types of DAT files.

How Can I Convert My DAT File?

Once you successfully opened the DAT file, you're at least halfway there to converting it. But once again, there are several options.

The Easy Solutions

Let's say we're dealing with a DAT file that originally was a DOC file. You changed the file extension, and now that you opened the file in Microsoft Word, it looks fine. In fact, you already "converted" your file. Congratulations!

If you managed to open the file with Word, the easiest way to "convert" your file from DAT to DOC, is to save the document using Microsoft Word. And there you go. It wasn't that hard, was it?

The Professional Solution: Winmaildat.com

Now let's get a little more serious. All the strategies above didn't work, and your file doesn't display properly. Maybe it's time to use a file converter.

If Microsoft Outlook messed with your email attachments, chances are that the online service Winmaildat.com will help you. If the file you need to decode is called "winmail.dat" or "ATT0001.dat," you have certainly come to the right place.

From the Home tab, click Choose File to browse for the DAT file on your computer. You can also enter a URL. Note that the file size limit is 10 MB. Click Start and wait for the results.

Winmaildat.com homepage screenshot

Winmaildat.com will tell you the file's origin, so you know which program to use to open it.

Your DAT File Sorted Out

That's all there is to DAT files. To successfully retrieve data from a DAT file or convert it back, you must know the source of the original file type or the type of file you're working with.