It is only until recently that people have started using eBooks. A few years ago, no one even knew about them. Perhaps we can say Project Gutenberg was what made people realize that books could be made into electronic formats. The most used format to read the text in these eBooks is PDF (portable document format).

Things are different now, they are a lot of eBooks available and the readership is also wide. People are spoiled for choice by the range of eBooks and are often confused by the eBook formats that are there. It therefore calls for a proper understanding of the difference in the popular eBook formats that are there that is EPUB, MOBI, AZW and PDF formats.

EPUB Format

It is short for electronic publication sometimes written as ePub, It is a free and open e-book standard by the International Digital Publishing Forum (IDPF).This is the likely the most commonly used format and supported by the largest number of e-Readers. Many e-Readers such as Adobe Digital Editions, Aldiko on Android, i-Books from Apple and many others support files that have the extension .EPUB. The EPUB reader can optimize text for a particular display device adapting itself to fit the available screen space as it is designed for reusable content, it also supports image file formats such as .GIF, .JPG, .PNG and .SVG.

MOBI Format

This is open standard eBook format works with the MobiPocket reader and Amazon kindle Readers. In 2005 it was bought by Amazon, this is believed to be the reason Adobe systems announced it would no longer sell eBook packaging and server software. It uses .MOBI or .PRC extension but can be changed to either of the accepted forms. Readers can add their own pages, annotations, freehand drawings, highlights, notes and corrections in MOBI formats as long as the device supports it. This is because it can take complex content; it supports indexing, include advanced navigation controls and also allows a high degree of compression. It can also reflowable content and fixed width layout. MOBI format is best suited for smaller screens as it has an image size limitation of 64K.

AZW Format

An AZW file is a kindle eBook format file. Amazon developed it for use by their array of Kindle eBook readers. This file format is the same as MOBI but has better encryption and compression rates. Its main disadvantage is that it does not allow the addition of series metadata to the file.

AZW includes Amazon’s own DRM (Digital Rights Management) which works by restricting usage of the file to the device I.D that is linked to the user details of the owner. This proprietary format is used for eBooks that need DRM protection.

PDF Format

Portable document format (PDF) made open from 2001 is the oldest eBook format and the most used. Due to it being so common with readers it offers tools that allows one to edit, create and secure PDF documents. It also supports reflowable content and fixed width layout. One can convert webpages to PDF and keep them archived with ease.

PDF is a file format that retains a document’s true formatting across platforms and is very useful for documents such as newsletters or financial statements that usually has complex formatting. It can be digitally signed and locked secured against any editing.


There are several formats, which can be very confusing. Luckily, several tools that allows as to convert formats like PDF to EPUB, MOBI to HTML or converting PDF for kindle readers. With the above guide, you shouldn’t have any more problems understanding these popular eBook formats. Which is your most preferred format?