A file with the .dat file extension is a generic data file that stores specific information relating to the program that created the file. Some apps that use them are CCleaner, Porteus, and Minecraft. They might even show up in your email as an attachment from a Microsoft Exchange Server. In short, a DAT file contains important information for software to handle. The information contained inside a DAT file is usually either plain text or binary, although in rare cases you might encounter them as the actual data of a video file for programs like VCDGear or CyberLink PowerDirector.