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.

If you're having trouble opening a DAT file, I'll show you a simple and free way to do it. This method works on both Mac and PC. Just open your browser and go to winmaildat.com. It's a ...

What is the deal with those winmail. dat files? I get them in my email all the time, and nothing seems to be able to open them.

Though DAT files, which house data as the shortened name implies, are usually best left alone, here's how you can open them.