docx In an effort to create an open document standard, Microsoft in collaboration with ISO/IEC and Ecma, developed the Office Open XML standard in 2006. One of the filename extensions supported in this specification is the .docx extension, a text document filename extension. The .docx was introduced in Microsoft Office Word 2007 and has been supported ever since in later iterations. It has become the default filename extension for all text documents produced using Microsoft Office Word. Given the open source nature of the XML specification, more alternative document processing applications support read and write capabilities on documents saved with the .docx filename extension. This is in comparison to the .doc filename extension which is a proprietary asset owned by Microsoft.
fb2 The .fb2 filename extension refers to the open XML based eBook format known as FictionBook. The file format was developed by Dmitry Gribov with an initial release in 2004, quickly gaining popularity in Russia. The format is open which in this context means it has no compatibility with digital rights management technologies. The structure of the format splits the contents of the data into three sections; title information, XML document information, and finally information about the paper edition which is optional.