The problem with files having .dat extension is that you do not know what file format they actually are. In other words, you do not know for which program is the file meant. It may be a simple excel worksheet or it might even be a media player file. How to open a dat file depends on the type of software it is meant for. So most of us must have figured out by now, that for opening these files, we do not have a special software. It can be any software. Nowadays, most of the programmers as well as people who are emailing files, avoid sending dat files. They would rather send a zipped file. But it's always beneficial to learn how to deal with the situation if you are confronted with one. What are Dat Files? Dat files are also known as detection definition files. These files are often used for detecting anti-virus or anti-malware programming code in a particular file format. They contain information in ASCII code. They are usually used for VCD files and in some cases for email attachments. However, there is no restriction to use a dat file for only these two data formats. It can also be a .doc file. Let us now try to understand, how to open these files. How to Open Files with a .Dat extension The basic question we are dealing with in this article is how to open a dat file. Opening a dat file is not a very difficult task. It does not require you to download a special software to do so. You may not even be aware of the fact, that the software is already installed in your computer. So, simply try to open the file in notepad. You can also use some advance text editor in place of notepad. If you can open the file successfully and you find that the data inside the dat file is in human readable form, then it was probably a text file. If in case you cannot recognize the information, then you do not need to panic. From whatever readable data you get in the file, simply try to figure out, what is that particular file probably meant for. If you find some tabular data information, then probably it is a .xls file, in other words, an excel file. With whatever idea you got from the data in the notepad, try opening the file in a different software. It is a simple trial and error method. Right click on the file and select, "Open With..." Select the option for choosing files from existing programs in your computer. Now try out different software. It can be any of the software that are already installed on your computer. If the data in the notepad file had many different type of characters, try media players and adobe acrobat reader. Also, check out the size of the file. If the file size is very large in hundreds of MBs, try out some media player, which can support different types of media file extensions. Suppose you find out that your file opens in a particular software, then you can simply change the file extension from .dat to the file extension that the particular software supports. Whenever you try to open the file again, it will choose the software itself. For those who do not know how to change the file name extension, let me explain you how to do it. It is a very simple process. First of all, try right clicking on the file and select "Rename". Check out if the file extension, .dat is visible. If yes, then simply change it. In case the file extension is not visible, then for that particular window, in which you have the file, go to the "Tools" menu and select Folder Options. In Folder Options, go to the "View" tab. Under the View tab, uncheck the option which says, 'Hide extensions for known file types.' Now press the ok button and try changing the name again. You will see the file name extension and you can change it successfully. Well, this was all about dat files. Simply keep in mind, that it does not require any special software, it is just some other file format which has been converted to this format for anti spyware and anti malware detection.