You can open .DAT files that contain text, with text editors, like Notepad, Notepad++, VS Code, etc. But it is not possible to know what contains in a DAT file.

Got a Microsoft Word doc that needs to be a PDF? A JPEG image you want to change to TIFF? Here's everything you need to know about converting file formats.

Right-click on the DAT file you want to open and select Open with from the drop-down menu, then choose the text editor. If the DAT file is a video, you can open it with its associated video app.