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MOBI Format and KF8: Making Sure Your Vellum Formatting and Illustrated Books Always Look Pretty

When you upload your ebook to BookFunnel, there is a checkbox to include the KF8 when we distribute your MOBI.

What is a KF8?

A MOBI file can contain two formats inside of it: the old MOBI format and the newer MOBI KF8. Most Kindles and Kindle apps will take your MOBI file, open it, and display the newer KF8 format. If you designed your book with pretty swirls, upgraded fonts, and advanced image options, then you need to check the KF8 box so that your readers will see those floopties (yes, that is their technical name). MOBIs generated through Vellum and other formatting software often require the KF8 in order to display the book EXACTLY as you designed it.

Should You Include KF8?

That depends on what you are distributing. A few issues to consider:

  1. File size. If you check the KF8, your MOBI file will likely be double what it would be if we only delivered the older format. This is a non-issue for some fans, but for Android and Kindle Fire readers, a 4 MB book may be too large for them to squeeze onto their already-at-capacity local storage. Also, internet speeds are very slow in many parts of the world, and a larger file may prohibit some readers from downloading it
  2. Kindle For iOS app won’t show your KF8, even if you check the KF8 box. It can ONLY read the older MOBI format when a book is sideloaded (meaning, distributed outside of the Kindle store). This means that your floopties and illustrations will not show up for any Kindle For iOS reader, no matter what.
According to our download stats, this accounts for about 30% of all book downloads on BookFunnel. Yes, this means that a lot of readers won’t see your floopties, even if you DO check the KF8 box and double your file size. This is not a critical issue if your floopties are non-essential to your book. However, if you have an illustrated book you will want to read this.

What will Kindle For iOS readers see?

They will see the older MOBI format, which is usually just a stripped down version of your book. The default font may be different, and the margins and chapter headings may be different. If you have used tiny images as scene breaks, those may not be in there. You can check the file yourself if you have an iOS device by emailing yourself the book and opening the emailed book in your Kindle For iOS app (or download it via BookFunnel).

Edit Your Current Book to Include KF8

You can edit your book and start including the KF8 easily, without interrupting your downloads or having to change any links.

To check the KF8 box:

  1. Click Books on your BookFunnel dashboard and then click the book title
  2. Click Edit
  3. Under Book Files, check the box to “Include the KF8 MOBI format (this will double your file size)”
  4. Click Save And Close

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