So you want to open that .dat file that you've found on your computer or have been sent by e-mail. Well, I hope you're ready for some bad news! The .dat file extension simply indicates that it's a data file and could potentially have been created by just about any program in existence.
Want some more bad news? The .dat files happen to be one of the most common file extensions in computing.
Now for some good news, maybe.
Firstly, if you have found the file on your computer, it's found location may give you a clue as to which program created it, which in turn may provide a clue as to which program can open it. Also, the date and time that the .dat file was created/last modified can sometimes help if you know what software you were using at that point.
And some more good news, maybe.
As the format of the data in .dat files is often specific to the software that created it, it's sometimes possible to open the file in a text editor such as notepad or editpad pro (for larger files) and manually scan through the contents looking for clues. Remember, never save the file after opening in a text editor, as you will probably lose the file's original format.
So in summary, there's no way of knowing which program can open a .dat file, as the .dat extension simply means data.