TrIDNet is described as 'TRIDNet is the GUI version of TrID, probably more practical to use than the CLI version, especially for those not very familiar with the command line prompt' and is an app in the Security & Privacy category. There are six alternatives to TrIDNet for Windows, Linux, Online / Web-based, Mac and BSD. The best alternative is TrID. It's not free, so if you're looking for a free alternative, you could try file or Toolsley File Identifier. Other great apps like TrIDNet are FileCHK (Free, Open Source), JHOVE (Free, Open Source) and HexBrowser (Free).
JHOVE is a file format identification, validation and characterisation tool. It is implemented as a Java application and is usable on any Unix, Windows, or OS X platform with appropriate Java installation.
HexBrowser is a tool that identifies file types. It does not care about the file extension, but opens each file to look for signatures so it can determine the exact type of a file. It now recognizes more than 800 different file formats.