Identifying a file type is normally just a matter of looking at the extension: EXE is a program, ZIP an archive, JPG an image, and so on.
But what if the extension is missing, or has been changed for some reason? Then HexBrowser.NET can help by analysing the file contents.
You can't drag and drop your target file onto the program, but otherwise it works as you'd expect. Click "Open", select whatever you like, and HexBrowser.NET's "Info" pane tells you more about it.
This starts with the basics: name, path, file size, create/ access/ write times, attributes and so on.
HexBrowser.NET then uses its knowledge of file structures to tell you the file type: a rar archive, a Windows bitmap, an executable, a Rich Text Format document, an internet shortcut, whatever it might be (more than 1,000 formats are supported).
HexBrowser.NET occasionally goes even further, giving you some low-level details of the file's innards. Click "Archive", say, and it won't just tell you the file is a "Zip archive": it'll also identify the number of files it contains, and list them individually.
This isn't always as helpful as it could be. When we selected an MSI file, the program didn't clearly tell us it was an installer, or even a program, instead identifying it as an "OLE2 Compound document". The lengthy report does contain more useful information (the "SummaryInformation" table has the keywords, "Installer, MSI, Database"), but you have to wade through plenty of other details to find it.
Still, HexBrowser.NET does a reasonable job, most of the time. And even if it can't identify something, built-in hex and text viewers mean it's easy to explore the file yourself.
It doesn't always provide all the information we'd expect, but HexBrowser.NET is still a handy way to find out more about mystery files.