The best way to open a .DAT file is to use the program that creates it. However, if you’re not sure, you can always try Notepad. Now when you open it in Notepad, you may be able to recognize some of the data, but the rest will most likely be junk spewed out by the program that creates it.
You’ll normally only see this file format when receiving emails with attachments. Most common programs today do not generate .DAT files and only computer programmers use these files on any kind of regular basis.
For some strange reason, some email programs automatically change the file extension on email attachments to .DAT. So if you receive a picture of DAT file, you first need to save it to your computer and then change the file extension to JPG or GIF or PNG or whatever you think it’s supposed to be. If you receive a Word document, change it to .DOC, etc.
You can change the file extension on a file by first going to My Computer, clicking on Tools and then Folder Options.
Next click on the View tab and then scroll down to the option “Hide extensions for known file types” and UNCHECK it. In this way, you will be able to see the file extension and change it to something else.
Now simply right-click on the .DAT file and change the file extension after the dot to the desired file format.
You should also see the icon representing the file change to the appropriate program used to open that file type, i.e. Excel in the above picture.
What do you do if you’re not sure which program it comes from or what the original file extension is supposed to be? You can try right-clicking on the file and then choose Open With and try different programs. For example, You can change one of your Excel files to a .DAT extension and then right-clicke on it to open it with Excel.
Then you just choose Microsoft Excel from the list and Excel is able to read the file since the data is written by Excel. It just has a wrong file extension.
You can also try other programs like Windows Media Player since it will open it if it happens to be a video, MP3, or similar media format. So hopefully you are now able to open your mysterious .DAT file using one of the above mentioned methods!