There was a time when reading books was the most preferred leisure-time activity. Delving into mysteries, we joined the protagonists as they took us to exotic places or science fiction, where we warped from one place to another in search for the next big breakthrough. From keeping pencils and bookmarks to marking where we left off, we made our ascent to the digital age where one touch solved it all. The digital revolution has changed our perspective of books. Books don't have to be encased in a special cover or wrapped in a plastic sheet to preserve its integrity. Rather, they have been reduced to an electronic format which can be downloaded at ease, called eBooks. The eBooks are available in different formats, each suitable for its own set of readers. This article tells you about the three formats currently trending in the online world, namely EPUB, Mobi, and PDF. EPUB The .epub format, called the electronic publication format, is an open-standard format created by the International Digital Publishing Forum. It's the most opted format across most eReaders including Nook (Barnes and Noble), iBooks (Apple), and Aldiko on Android, and is widely supported across all platforms. Basically, it defines a way of packaging and representing the web content in a single-file format. It contains an XHTML file with a navigating index for its chapters. The latest version available is EPUB 3.0.1. PDF PDF, made by Adobe, stands for Portable Document Format. It is the oldest eBook format available and is the most commonly used of all formats. The best part about this format is that it can be viewed and printed on any platform. Also, the files can be secured and locked for editing with the help of digital signatures. PDFs preserve the original layout of the document with any type of data including text, images, drawings, multimedia, 3D, maps, full-color graphics, photos, and videos. Mobi Mobi is based on an open-standard eBook format using XHTML and JavaScript. It stands for Mobipocket eBook format, and is the most preferred format by Amazon Kindle. Images in mobi eBooks are limited to a 64 KB size. It runs on all platforms except Android. Mobi also supports fixed-width layout and reflowable content like EPUB. It contains advanced navigation controls and supports file compression, indexing, and dictionaries. The files can have the .prc or .mobi extension. The distinguishing features that make each of them unique are as follows: Readability PDF contains static text accompanied by images and multimedia which has to be zoomed in to view the display in case of smartphones and tablets. EPUB and Mobi supports reflowable content which resizes the text according to the device. The user can just flip pages to read further. Multi-Platform PDF is supported on all platforms which gives it a distinct advantage over its rivals. EPUB is an upcoming format that's easily accessible and can be easily converted to other eBook formats. It runs on all platforms except Amazon Kindle. Mobi files are only readable in the proprietary Amazon Kindle program. Versatility PDFs can be edited or saved in different formats. Mobi and EPUB have read-only functions and cannot be edited. Extensibility PDF has a bigger reach and popularity since it has been available since 2000. EPUB and Mobi are recent formats and will slowly gain popularity across the masses who use smartphones and other devices. Security PDF has digital security to protect its data from intruders. Mobi has Digital Rights Management (DRM) to protect its data from plagiarization. Since EPUB is an open format, it doesn't have DRM and can be distributed and shared easily. All the eBook formats have some advantages over the others. While some pertain to usability and portability, others have conditioned it on trust. Whether you are a published author or someone who wishes to pass on encrypted information, we leave the choice of file formats to you.