By David Kudler
The majority of people who read ebooks (in the English speaking world, at least) buy them on Amazon. That means, most likely, reading them on a Kindle.
But what “reading them on a Kindle” means varies a lot more than you may realize. And understanding those variations at least a little is important for an ebook publisher.
Mobi/Kindle: the Frankenstein Monster
If you’ve ever looked at the files on your Kindle or downloaded a file from KDP for preview purposes, you may have noticed a bewildering variety of file formats: mobi, azw, azw3, kfx, azk, and more.
In fact, those are all simply Kindle files optimized for different versions of Amazon’s ereaders — pre-2010 Kindles, old iPhones and iPads, Kindle apps for computers, newer Kindles, etc.
When you create a Kindle ebook using Kindle Previewer or download one from KDP, you’ll get a file that ends . mobi. Inside, it contains the two file formats that serve as the basis for that alphabet soup of variations:
- mobi — An old-style Palm Pilot Mobipocket file for old Kindles (aka MOBI7) and some older versions of Kindle apps
- kf8/kfx — A newer file format based on ePub3 that works on all new Kindles and Kindle Apps
So those “mobi” files are actually a Frankenstein monster, grafting an older (fairly limited) ebook format into Amazon’s variation of the current standard. The older mobi format has much less finesse than the newer kf8/kfx in terms of typography, images, metadata, and all around formatting. However, there are still millions of those older Kindles around, and so Amazon happily embraces and supports them.
The good thing about those Franken-files is they should load on most new and old Kindles and Kindle apps.
The not-so-good thing is that there’s no way (currently) to edit those files directly. So if you spot any content or formatting problems, or have updates you’d like to integrate, you’ll either have to work from the original file (whatever format that may have been in) and go through the conversion process from scratch, or convert from mobi to an editable format like ePub.
From a publishing point of view, there’s probably not a huge amount you need to be worried about with regards to the differences between the two embedded formats — if your book is simple, with few or no images and relatively straightforward formatting.
If you have inset images that text wraps around, drop-caps, tables, indented verse, or other fancy grace notes, you’ll need to add some @media queries that allow you to optimize your ebook’s CSS for both old and new Kindles. (That’s a longer, more technical post; I’ll cover that next time.)
Creating and Editing Kindle Files
There are essentially four ways to create a Kindle file:
- Convert using a computer app such as Calibre, Kindle Previewer, or the Kindle Creator app
- Export from a writing/publishing app like InDesign, Sigil, Scrivener, Jutoh, etc.
- Upload your base document (ie, Word doc or ePub file) to KDP
- Use the KindleGen Java applet in your computer’s command line (if you’re geeky like that)
In reality, of course, they all amount to the same thing, since the conversion apps and KDP all use KindleGen. In general, you should use whichever tool best fits into your workflow.
Nonetheless, there are a few distinctions that are worth considering.
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