iBooks Author is an e-book authoring application by Apple Inc. Books created with iBooks Author export as ".ibooks" files and can be published to the Apple iBooks Store, or they may be exported as PDF. Apple released iBooks Author on January 19, 2012 at an education-focused special event in New York City. Simultaneously, Apple also released iBooks 2 and a new iBooks Bookstore category for textbooks. The software is proprietary and available only for macOS. Apple offers it for free download in the Mac App Store. Apple describes iBooks Author as a tool for "educators and smaller publishers to create their own books". Documents created by iBooks Author may only be sold for a fee if they are accepted by and distributed by Apple, but authors also have the option to distribute their work anywhere if the work is being distributed for free. Many aspects of a document may be edited in WYSIWYG fashion, including text, fonts, colors, foreground and background images, interactive widgets, and charts. Tables of contents and glossaries may be managed with some automation. The user interface and editing features have been described as nearly identical to Apple's Keynote and Pages products. Apple clarified its position on rights of ebooks generated by iBooks Author on Feb 3, 2012 to address some controversy that its ebooks could be sold only through the Apple Bookstore, specifying that only books carrying the.ibooks suffix were subject to such restrictions. Apple also specified that the use of the software to create text or PDF files are within the terms of its user agreement. To offer your book on the iBookstore, an International Standard Book Number, or ISBN, is recommended but not required. An ISBN is a standardized identifier for books and is necessary for industry-wide sales charts and data sharing. Note that you can only provide an ISBN during the initial book delivery. The output of iBooks Author is a proprietary Apple file format similar to the EPUB standard, but with extensions that prevent it from being universally readable or editable as an EPUB document. The format uses undocumented, proprietary XML namespaces and undocumented extensions to CSS. A new version of iBooks Author was released on October 23, 2012. It includes embedded fonts, mathematical equation rendering, and more interactivity options. On October 22, 2013, iBooks Author received another update which included compatibility with OS X Mavericks. On October 16, 2014, Apple updated iBooks Author to version 2.2, adding several new features, namely EPUB import, InDesign IDML import, and the addition of a blank template for ease of use. On June 30, 2015, Apple updated iBooks Author to version 2.3, adding two significant new features: iPhone compatibility for Multi-Touch Format books created in iBooks Author, and export of EPUB-format books created in iBooks Author. Further, the terms and conditions of iBooks Author were changed to allow iBooks Author users to monetize EPUB-format books exported out of iBooks Author any way they choose. On October 7, 2015, Apple updated iBooks Author to version 2.4, adding minor updates including the new ability of EPUB-format books created in iBooks Author to use the Pop-Over widget, as well as minor enhancements to the interface and to EPUB-format book function. Version 2.5 was released in late 2016. iBooks Author adoption has grown since version 2.2's release leading to the creation of the iBooks Author Conference which has taken place in Nashville, Tennessee, in October 2015 and October 2016. A follow-up conference for 2017 has been announced, keynoted by NASA astrophysicist Dr. Scott Bolton.