One of the most versatile file extensions is the dat file. Owing to this versatile nature of this file format, there is not defined structure for the dat file. Typically, it can be just about anything you can dream of since this is just a data package.
They are generic data files which can be generated by any application either as a dump file or as a binary data file. The most common dat file structures can be attributed to them being text, graphic, binary data and structured data.
If you receive a dat file in your mail or if you come across a dat file on your computer, your best bet would be not to attempt to open it unless you absolutely have to. Unless you know that it is from a trusted source or editing it would not be a problem, it is best to leave it as it is.
The most common dat files that you may come across are package files in video CDs. If you attempt to open a movie VCD on your computer, you will find some application files and some dat files.
These dat files are the essence of the VCD and serve as the data packages.
The applications bundled with them are used to open these files. These files can be opened with the help of a normal media player if you have disabled Auto run on your computer.
Just because you opened dat files on the VCDs with a media player, it does not mean that every dat file can be opened that way. For instance, index.dat is a common file that is used to store the history of most browsers. If you have checked the box which enables you to see hidden files, you will be able to see this file in the folder where your browser history is located.
When you are updating your anti-virus applications, you will notice that all the updates are in the dat format. As these examples indicate, dat files are specific to the application that was used to create them and the ones that are designed to run them.
If you want more information on which application you need to open a dat file, use a text editor like EditPlus to open the file; this might give you an insight into the file in most cases but binary data files provide no information.