IRS provides forms and publications in the file formats described below. Portable Document Format (PDF) PDF is a file format that represents the printed paper versions of our forms and publications. PDF files can be read, browsed, searched and printed using either the freely available viewing program, Adobe Reader, or other programs capable of reading PDF files. ePub (.epub) ePub is an international digital publishing standard developed and maintained by the International Digital Publishing Forum (IDPF). It is a file format that can be viewed on mobile devices (such as a smart phone, or tablet) that have an eReader application installed. ePub files are created to be accessible by the visually impaired or blind. ePub files can be searched, bookmarked, linked to the internet, and will reflow text to fit any digital screen for a better reading experience. Standard Generalized Markup Language (SGML) SGML is an international standard (ISO 8879) for defining and identifying the structure and content of documents. SGML files are plain text files that contain element identifiers or "tags" that identify the content and structure of a document (e.g., chapter, paragraph). SGML provides a syntax for describing these tags, their use, and their relationships. HyperText Markup Language (HTML) HTML, an SGML application, is used to define and present documents for web based applications. HTML contains a limited, fixed set of "tags" or markup to describe the content and structure of documents. Browsers (Internet Explorer, Firefox, Chrome, etc.) interpret the markup and present the content. Extensible Markup Language (XML) XML is based on SGML and was developed with the needs of the Web in mind. It is more flexible than HTML and has fewer restrictions than SGML. XML has been designed for ease of implementation, and for interoperability with both SGML and HTML. Text-Only (.txt) Files These files are versions of IRS forms and publications that contain only ASCII text to allow compatibility with adaptive technology. All tables and graphical content are presented in text-only format to assist taxpayers who are visually impaired or blind. Text-only files can be opened by any word-processing program, including Microsoft Word, Notepad, and Wordpad. These files cannot be filled out or submitted to the IRS, but they present the information in an accessible manner. Braille (.brf) Files These files are formatted for printing through a Braille embosser to assist taxpayers who are visually impaired or blind. Sending these files to an embosser will produce a Braille version of the form or publication. Taxpayers cannot submit .brf files or hard copy Braille to the IRS, but they provide valuable tax information in Braille format.