How to Open a DAT File (Identify the Type First)
A .dat file isn’t one format, so there’s no single way to open it. Find out where yours came from first, then use the matching fix below.
A file that ends in .dat can be almost anything. That is why searching “how to open a DAT file” rarely gives a useful answer.
.dat just means “data.” No single program owns the format.
So the real first step is not opening it. It is figuring out where this particular .dat came from.
Match your file to the table below, then follow that section.
| If your .dat… | It is most likely… |
|---|---|
| arrived as an email attachment | winmail.dat from Outlook |
| came from a game or app you use | that program’s private data file |
| sits inside an MPEGAV folder on a disc | a VCD or DVD video track |
| opens in Notepad and shows readable words | a plain-text config or log file |
| gives you no clue at all | unknown, so identify it first |
First, figure out what your .dat actually is
Three quick checks cover most cases:
- Where it came from. An email? A specific app or game? A CD or DVD? The source usually tells you everything.
- The file size. A video .dat is large, often hundreds of megabytes. A config or email attachment is much smaller.
- A peek inside. Right-click the file and open it in Notepad. Readable words near the top often name the originating program. Close without saving.
Most .dat files that are not plain text will show scrambled characters in Notepad. That is normal and does not mean the file is broken.
It is also worth confirming the extension is really .dat and not something hidden. If you are unsure, here is how to show file extensions in Windows and see the real type.
winmail.dat: the most common case
This is what most people run into. winmail.dat is not a mystery format. It is an Outlook quirk.
When someone sends from Outlook with “Rich Text” formatting turned on, Outlook wraps the real attachments inside a TNEF container. The resulting file is named winmail.dat. Other mail apps have no idea what to do with it.
You have two options:
- Ask the sender to resend. In Outlook, they should switch the message format from Rich Text to HTML or Plain Text before sending. The real attachment arrives normally this time.
- Use a TNEF viewer. Free tools like Winmail Opener or Letter Opener can extract the actual files from the winmail.dat container. No need to ask the sender to do anything.
If the .dat came as an email attachment and you were not expecting a .dat file, winmail.dat is almost certainly what it is.
Program data files
Many apps and games save their own data files with a .dat extension, like a save file, a cache, or a settings store.
These files are meant for the program that created them. Opening them by hand usually shows scrambled data that means nothing outside that program.
The right approach is to open the program itself and let it read the file the way it was designed to. If the program is gone, the .dat is usually not useful on its own.
Some data files are also tied to a specific disk layout or installation path, so copying the .dat alone does not always restore your data.
Video .dat files
Some older VCD and DVD discs store video tracks as .dat files inside a folder called MPEGAV. They look unusual but they are just MPEG video with a different name.
VLC can usually play these directly. Open VLC, go to Media, then Open File, and point it at the .dat. No conversion needed in most cases.
If VLC does not recognize it, try renaming the file from something.dat to something.mpg and opening it again. The content does not change. For another file type that needs similar detective work before you can open it, see the guide to opening BIN files.
Plain text .dat files
Some programs save configuration, log, or export data as a .dat even though the contents are just plain text.
If you opened the file in Notepad and could read it, you are done. It is already open and human-readable.
Notepad or any plain text editor is the right tool here. You can copy the contents, edit them if you know what you are doing, or just read the values. Do not use Word or another rich-text editor because those add formatting that can corrupt the file if you save.
A quick safety note
You do not need a special “.dat opener” program. Most of the time the fix is simpler: ask the sender to resend, use VLC, or open the originating app.
Many sites that promise to open any .dat file are bundling adware or worse. If a search result pushes a download to unlock your .dat, close it.
Stick to well-known tools like VLC and get them from their official sites.
Frequently asked questions
Why does my .dat file look like gibberish when I open it?
Most .dat files are binary, not text. The scrambled characters are normal. The file is not broken; it just needs its own program to read it.
Can I rename a .dat to something else to open it?
Sometimes. If the file is really an MPEG video, renaming it to .mpg can work. But renaming a binary data file to a format it is not will not fix it.
Is it safe to delete a .dat file?
It depends on where it came from. A winmail.dat from an email is safe to delete once you have extracted what you need. A game’s save .dat holds your progress. Check what it belongs to before deleting.
Why did the sender’s email arrive as winmail.dat?
Their Outlook is set to send in Rich Text format. Ask them to switch to HTML or Plain Text in their compose settings. That stops it from happening again.
