Amazon .mobi and .azw File Format v.s. .epub File Format – What’s the Difference? – Part 1

The Killer Whale:  .Mobi Dick

For most people converting a book to digital platform, Amazon is the first stop on the whistle tour.  They have the largest number of sales and the conversion process is touted to be fairly simple.  Compared to .epub, I think it is simpler, more forgiving, but still not simple.

Theoretically, at Amazon I can take a document, save it as an .html file format and upload that bad boy to Amazon Digital Platforms.  Yeah.  I can also run copies at Kinkos, but that doesn’t make it a paperback.

For me, the finesse of formatting is tapping into the functions that Kindle or another ereader makes available to the end user.  I want an active Table of Contents, Joystick Chapter Jumps, active Progress Meter, and an embedded cover in the file.  I’ve seen many traditionally published books, through major imprints, which don’t allow the use of Joystick Chapter Jumps (push the joystick left or right and it jumps sequentially from chapter to chapter).  One such book was a ‘For Dummies’ book, which is inexcusable for a non-fiction read.

Amazon uses a .mobi format, which is equivalent to the .azw format, but with different DRM.  The .mobi file can be read directly through your Kindle.  The .mobi file is generated from three other files, plus any graphics I want displayed, such as the cover art.

Please note: I never edited the .mobi file.  I generated it.

Generating the .mobi file is the last step and easiest step in the process.  I generated the .mobi file using a free piece of software from Amazon called Kindlegen.exe.  It is run at a Command Prompt line.  Anyone familiar with the old DOS prompt will recognize this.  But there’s a lot of important preparation before getting to this point.  I’ll detail all of these steps in other posts.

At a minimum, I needed three files to generate the file for my novel, 3 LIES.  These were 3LIES.opf, toc.ncx, and 3LIES.html.  I included quite a few graphic files– either .jpg or .png — for my cover art, the title logo, my signature, and my photo, but these are not required to generate the .mobi.

I included a cover art file because I wanted readers to be able to see it when they read.  Readers can use the Menu button, then “Go to” “cover” to see this image.  I still needed to upload the cover art file at the Kindle website, so it shows up when people are shopping.

The .opf file is the build file. It contains the instructions to the Kindlegen.exe program on what to do with all the other files, what to process, what to include.  I edited this file in Macromedia’s Dreamweaver (reasons why later, not free), but any text editor or html editor will work.  Notepad ++ is a good one.

The toc.ncx is the Table of Contents file (toc) which contains the navigation controls for the xml code (.ncx).  Here I can define Joystick Chapter Jumps for use with the Kindle joystick, plus the “beginning” point of my book when it is first opened.  Readers can also get here by using the Menu button, then “Go to” “beginning”.  For most reads, the beginning should be Chapter One, page one.

The toc.ncx file keeps the same file name for every new ebook, but the information inside will be different.  For each .mobi file, representing a new ebook, I create a separate folder on my computer to keep these separate. I edited this file using Dreamweaver.

The .html file is where all of my soul-tussled words reside.  All the words that appear in my book, whether special pages or part of the story, follow in sequence in a single continuous file. All ninety of my chapters are here.  Each chapter or section starts and ends with specific code to keep these separate.  More on this another day.

In 3 LIES, I included several non-chapter pages such as a dedication page, acknowledgements, and another table of contents.  Oh joy.  The table of contents in the toc.ncx file serves a different purpose.  This table of contents defines html anchors for the chapters and sections.  Within the Kindle, it appears as a list of links at the beginning of your ebook.  When I use the Menu button, then “Go to” “table of contents”, this is where I land.

My table of contents had links to all the non-chapter pages listed, plus all ninety of my chapters, making it several pages long.  The reader can use the joystick to toggle down to a particular chapter and jump directly to it.  These table of contents links are not the same as the Joystick Chapter Jumps I described earlier.

Confusing, eh?  If you have any questions, please let me know.  If you have anything to add to this, please do.

And if this series has made the formatting process easier for you, please consider purchasing one of my novels for yourself or a thriller lover in your life.  Here are the links:

iBookstore – Amazon – Barnes & Noble

Amazon UK – Amazon DE – XinXii


Other Posts in This Series:

Part 2 – .Mobi File Format vs .EPub File Format Overview

Part 1 – .Mobi File Format – HTML Component

Part 2 – .Mobi File Format – HTML – Table of Contents

Part 3 – .Mobi File Format – HTML – The Chapters

Part 4 – .Mobi File Format –  Toc.ncx File

Part 5 – .Mobi File Format – .Opf File

Part 6 – .Mobi File Format – Kindlegen Your .Mobi

Kindle Promises Here



Photo by Mike Baird