What is that file extension?

You can look up the information about desired file extension and its file associations using File-extensions.org website. Simply use the search box in the top-left corner of each page tosearch for a specific file extension. You may also view an alphabetical list of extensions using the starting letters above, or browse by file type using the links on submenu at the left side of the page.

Link:
http://www.file-extensions.org/