How to convert Kindle KFX books

how to convert fkx booksMore and more Kindle users are telling me that they have Kindle books with “.kfx” format, when they transfer these books from Kindle eReader to computer, Kindle for PC/Mac and Calibre both can’t read it, the Calibre also can’t convert it. So what is the file with extension name “kfx”? Is it really a book? How can I read it on computer? How can I convert it? I believe these question are uncommon if you also encountered the “.kfx” files.

Let me explain the first question: What is “.kfx” file.

To make it simple, “.kfx” is the new format of Amazon Kindle eBooks. In fact, it’s only a downloader, when you buy a Kindle book, your Kindle will receive this “.kfx” file, then the “.kfx” file starts to download all the contents of the book. Why Amazon make the process so complex? For better reading experience. If your network is poor, the “.kfx” file downloads the basic version of the book (like the image are all having low resolution), when your network is good, it will download the nice version to replace to basic one. You are not aware of this entire process, everything looks like the old way, you buy a book, the books is downloaded, then you start reading.

How to get a “.kfx” book?

Currently you need to meet these two requirements:

  1.  The book is downloaded into a Kindle eReader which has the firmware version higher than 5.6;
  2. On the Kindle book’s Amazon product page, you can see “Enhanced Typesetting: Enabled” under “Product Details”

How to convert a Kindle KFX book?

As I explained in the first question’s answer, the “kfx” file is not an eBook document file in actual, so it is impossible to convert it to any eBook format like EPUB, PDF, AZW, Mobi, etc., Calibre’s developer commented on this problem like this: KFX is not an actual format, it is a bundle of separate files, and it is encrypted, so it is not possible to convert to it.

Convert Kindle KFX to Mobi, EPUB, PDF AZW3 in two solutions:

Update: On 18th, October 2017. The software called Epubor Ultimate makes it possible to remove DRM from KFX books directly and loselessly.

You can buy this software with 20% off here:

With the software above, you can remove DRM from KFX books without any tricks introduced below.

Solution A:

  1. Go to’s “Manage Your Content and Devices” page.
  2. Choose a book, click the “…”(Actions) button, choose “Download & transfer via USB”. Then a float window will pop up, there you choose the Kindle eReader you are using.
  3. Load this downloaded file into Epubor Ultimate Converter, it would ask you to input KSN, now we input the serial number of the Kindle.
  4. After inputting KSN, this book is decrypted now, we can convert it to any format as we want.

Where to check a Kindle’s serial number(KSN)?

Go to your Kindle’s home screen, click “Menu” –> “Settings” –> “Menu” –> “Device Info”.

Solution B:

  1. Install Kindle for PC/Mac.
  2. Login your Amazon account and download the book to computer.
  3. Open Ultimate Converter and convert this book, with solution B, you needn’t input KSN or any other digits.

Some thoughts of KFX

Through KFX we can see Amazon’s “boiling frog” strategy, the Kindle ecosystem is and will become more and more closed. And another truth is, Amazon is actually monopolizing the eBooks industry slowly but steadily, maybe years later, we would have only one choice when we want to read an eBook, and that would be the apocalypse of the entire industry.



Please disable your adblocker or whitelist this site! I need the money to feed my kids. Please!

Pin It on Pinterest

Share This