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

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

  1. John Chapman says:

    I can’t help thinking you are using a sledgehammer to crack a walnut here. There’s a much simpler method to achieve what you want. here it is copied from my post at the Kindle User’s Forum:
    Here’s how I do it starting with a Word 2010 document with chapters headings set as headings style:
    1. Save the document as a html (filtered) file
    2. Open Calibre (
    3. Use the ‘Add Books’ icon to find the saved .html file and add it
    4. Select the added book and click the Edit metadata icon
    5. Correct the Title, Title sort, Author(s), Author sort, Series and Number fields as necessary
    6. Browse for my book cover file
    7. In the comments section add the text which would normally appear on the back cover of a book
    8. Click OK
    9. Re-select the book and click the Convert books icon
    10. At the left select the ‘Table of Contents’ icon
    11. Place a check in the ‘Force use of auto-generated Table of Contents’ box
    12. Select the output format required (Mobi)
    Click ‘OK’ and wait until the ‘Jobs’ icon bottom right indicates the conversion is finished – Repeat from 9 if you want an epub file also.
    The finished file will contain the correct table of contents you need, cover & meta-data description ready to be uploaded to kindle or sent to Amazon Digital Text Platform. You can find the file by clicking the Path Click to open link at the right of Calibre

    Of course you can tweak the code manually in Dreamweaver or other html editor (Although as an experienced Web designer the LAST one I would use is MS FrontPage). In most cases you won’t find it necessary, even if you add extra graphics within the book content.

    • Helen says:

      Thanks for posting, John.

      To me, all that matters is the output. If this achieves the same results, I’m good with finding easier ways to accomplish a task. Do you get the joystick chapter jumps using this method?


    • I tried these steps and all Calibre succeeded in doing was trashing the TOC and losing the formatting of the text.

      • Helen says:

        Hi Ande,

        Which steps in particular? Are you referring to John’s post?

        I must say, I’m loathe to change my process in any wholesale way because I know it works. My only goal is to get my book published. Well, and sold :)


  2. Alisa says:

    Can you give us a rundown on exactly how you made your title image for the title page? I am strictly a word person, so the image stuff has me very confused!

    Thanks for the great post!


    • Helen says:

      I know my limitations. The title image is the work of my cover artist. I asked him to give me a separate file specifically for this purpose. The best money I ever spent . . .

      The only image I created was the Domino Ink logo. It started as a photo of two dominos on my writing desk. Using Paint Shop Pro, my husband added a shadow effect (not sure how). I used the negative image effect and then added a metallic effect. For my paperback, I used the positive image since it was a black cover. My artistic capabilities hit redline for this project . . .

      All the best!

    • Fred says:

      It’s been a while, so I hope Alisa, who asked, is still watching. Anyway:

      A basic way to use Word to generate a title page might start by setting up a three-rowed table, with one cell per row: all rows 6″ wide; first row 2″ deep, second row 5″ deep, last row 1″ deep. What goes in these rows?

      Top row: text for Title and for Author, in whatever attractive font you like, in a type-size anywhere from 24 to 72 points, whatever suits the circumstances.

      Second row: a 6″ x 5″ graphic image (photo, whatever) — Insert | Image .

      Bottom row: your publication house name (here, for example, Domino INK
      maybe, or Helen Hanson Press, or what-have-you), in whatever font and type size seems appropriate (probably something between 18 and 42 points).

      That’ll give you a 6″ wide, 8″ tall cover. Print it “to PDF” (one of the things Word can do — or use the Windows free-ware BullZIP PDF Printer). Now take that PDF file, convert(*) it to a Jpeg or .PNG file at 100 ppi, and you’ve got the 600px x 800px graphic file you need for a cover illustration.

      (*)Convert it? you ask? — Here’s one quick and dirty way: view the PDF in Adobe Acrobat. Rotate it sideways so it appears in landscape position. And now a bit of trial and error: take a ruler, measure from L to R how wide that rotated image appears on your screen, adjust Adobe Reader’s Zoom level until that image is as close to exactly 8″ broad as possible. and then “scrape the image off the screen”.

      By that I mean: press [Alt]-[PrtSc] , start up MS Paint, and (once the cursor has clicked once within the Paint window) press [Ctrl]-[V]. You should see a duplicate of that landscape-rotated cover turn up in the Paint window. Of course, it’s surrounder by all the extraneous Adobe Reader garbage, so crop bottom and right appropriately, rotate 180 degrees and again crop bottom and right appropriately, and rotate 180 back again. Now ask Paint how wide and how broad that image is (different ways to ask, for different editions of Paint — Image | Attributes for the Paint in Vista or in XP; for Win 7, you’re on your own :-)).

      If the answer is exactly 800 wide and 600 high, you’re virtually down: rotate the image in Paint back to vertical and save it as Cover.png or Cover.jpg (or one of each). But if it’s not, determine to either increase or decrease the Zoom level of Adobe Reader to help the next iteration get closer to the figures you want, scrap this test image (close Paint without saving), go back to Adobe Reader, readjust that Zoom level, for a number of inches suitable for the ratio test

      desired inch measure : 8″ : : 800 : width Paint reported .

      (Remember those grade school “a is to b as x is to y” or “a : b : : x : y” exercises? This is where they come in, in real life :-) !) You want a = (bx) / y , of course, with b=8, a=800, and y=[width Paint reported] — adjust the Zoom level to deliver that “a inch” width figure and try again.

      This way won’t take more than three or four iterations before you’ve got just exactly what you want. Remember you can fudge a bit as you’re cropping, too :-) .

      HTH. And I hope I’ve not committed some infantile arithmetic gaffe. Cheers, — Fred

  3. Sunny says:

    I used Microsoft Front Page to do my website. I would love to convert it to an ebook (Kindle) and get it into the hands of crusiers and travelers. I am a total techy nyophyte and have struggled with the code part–for years! But the site has about 800-1,000 hits a day.. Is there any hope for me to convert my travel website to Kindle? Just got this bright idea yesterday–and I’m 78!! Hurry! (Smile)

    • Helen says:

      Congratulations, Sunny! It sounds like a popular site.

      Since your text is on a website, you will likely need to structure the information into chapters first. You can clip and paste it into Word for that purpose. But text is text. Once you have the manuscript completed to your satisfaction, the process is identical. Take care.


  4. Wheat says:

    Wow, you rock. I’ve just started my own voyage into Kindle publishing, and nowhere could I find a clear breakdown of all I needed to know to get the TOC and joystick chapter jumps working. I stepped through your entire series, tweaking my HTML, NCX, and OPF, as I went. And then enjoyed my first warning-free build with a perfectly functional TOC and NCX. I’m grateful to you for explaining this all so clearly and with so many full-length examples. I finally have my Kindle mojo workin’.

    • Helen says:

      It’s always nice to start the day with comments like these . . . Thanks.

      I’m glad the series was helpful to you. All the best!


  5. Great article really enjoyed it. Due to all of these different eBook formats eBook formatting is a necessity. Tons of people don’t realize that one format dosen’t get you on all of the eReaders, and mobile devices you need to be formatted to not just ePub but all formats that you mentioned such as .mobi. Again great article.

  6. Debbie says:

    I’ve used your instructions for Kindle formatting and have something to add to the instructions on the actual .Mobi writing process for Mac users:

    1. Download the KindleGen for Mac to your Desktop.
    2. Rename the unzipped folder “KindleGen” and throw away all but the actual “kindlegen” Unix file.
    3. Save a copy of your finished files (using Helen’s instructions) into this new folder.
    4. Launch Automator (it’s in your Applications directory). It will ask you to choose a template for your workflow–select “Service”.
    5. In the top right side of the Automator interface, change the settings so that this workflow will receive selected files or folders in
    6. On the left side under “Library,” click on the “Utilities” folder, then from the options that appear in the other column, find “Run AppleScript” and control click/drag that over to the blank area to the right.
    7. Select the default code in the “Run AppleScript” box and delete it. Copy and paste the following script in its place:

    on run {input, parameters}
    set myFile to quoted form of POSIX path of input
    tell application “Terminal”
    do script “~/KindleGen/kindlegen” & ” ” & myFile & ” ” & “-c1 -verbose” in window 1
    end tell
    return input
    end run

    Click the hammer icon. The code you just pasted will be activated.

    9. From the “File” menu at the top of the screen, select “Save As” and name it “Run-KindleGen.”
    (If you need step-by-step help on the AppleScript Automator part, go to:

    10. On your Desktop, open the “KindleGen” folder containing the app and your files and Control Click on your .opf file. You will see the newly created Automator script at the bottom of that Control option screen. Select it and watch the file writing process from inside your *Terminal app. If successful, you will see a new file called .mobi inside your KindleGen folder.

    Also Helpful for these final steps are the Kindle Previewer app (from Amazon). You can open your .mobi file to view how it looks inside a Kindle on your Mac and make adjustments to your .html file. Once your changes have been made, rewrite the .mobi file by simply “control click/Run-KindleGen” on your .opf file.