EPUB file extension is used to store e-books in EPUB file format. EPUB is short for electronic publication and is a technical specification developed by International Digital Publishing Forum (IDPF). EPUB file format is quite popular and is supported by many e-book readers and e-book software.
EPUB file is a compressed folder which stores files with e-book contents and layout. In some way it is easy to compare EPUB file to a small website with e-book as a content. Actual text of the e-book is stored inside one or multiple XHTML file. XHTML files could be rendered by a web browser if needed. E-book contents is stored in OPF file (typically as a content.opf). OPF is an XML based format which stores references, font and styling information related to each chapter of the book. Also, it stores e-book identification information such as ISBN, author and language of the book.
You can open EPUB file on Windows or Linux using free and open source Calibre e-book reader. Calibre also can process EPUB files and convert them to a different e-book format. This may be required to view EPUB file on Amazon Kindle device. Even though EPUB is technically supported by Amazon Kindle, there are several limitations to how EPUB file should be structured. That is why it may be easier to convert EPUB file to a different format such as MOBI, RTF, HMTML or PDF for better Amazon Kindle experience.
To open EPUB file on a mobile platform you can use Apple Books for iOS and Aldiko for Android. Or you can also use Bluefire Reader supported both on iOS and Android operating systems.
EPUB files are save for download and don’t contain scripts. You may open EPUB files downloaded from the internet without being afraid to infect your computer.