TrID is an utility designed to identify file types from their binary signatures. While there are similar utilities with hard coded rules, TriID has no such rules. Instead, it is extensible and can be trained to recognize new formats in a fast and automatic way.
TrID has many uses: identify what kind of file was sent to you via e-mail, aid in forensic analysis, support in file recovery, etc.
It uses a database of definitions which describe recurring patterns for supported file types. As this is subject to very frequent update, its made available as a separate package. Just download both TrID and this archive and unpack in the same folder.
The database of definitions is constantly expanding; the more that are available, the more accurate an analysis of an unknown file can be. You can help! Use the program to both recognize unknown file types and develop new definitions that can be added to the library. See the TrIDScan page for information about how you can help. Just run the TrIDScan module against a number of files of a given type. The program will do the rest.