FileInfo.com is described as 'contains a searchable database of thousands of file extensions with detailed information about the associated file types. You can use FileInfo.com to lookup information about unknown file types and find programs that open the files'. There are four alternatives to FileInfo.com, not only websites but also apps for Windows, Windows Explorer, Android and Mac. The best alternative is OpenWith.org, which is free. Other great sites and apps similar to FileInfo.com are File-Extensions.org (Free), WikiExt (Free) and FileFormat.com (Free).
FileFormat.com is your File Format Guide. It gives comprehensive information, news, and discussions about popular File Extensions. Visitors can find Description as well as History of file formats with respect to their development phases.