Hi, I have been using TrID for some time since I came across this software a few months ago and I must say I really like it a lot. Not sure if I'm correct but TrID does use some form of magic number (i.e. the header byte information in the <FrontBlock>) in helping it to recognize the file type. One suggestion is to add in a <EndBlock> to incorporate some footer information/ pattern which will definitely aid in forensic analysis in situations of concatenated files etc. Lastly, wish to stress again that TrID is a great tool, thanks for the tool!