Imagine that you download an ePub file from an online library and you want to read that book on your newly purchased Kindle device (such as Kindle Scribe), then what should you do? For a long time we are told to convert the ePub format book to Kindle AZW3 format. Yes, it works for a long time, but things are changed in May 2026, especially if your Kindle device is released after 2024.
Amazon blocks the AZW3 format books' viewing on newer Kindle models. Yesterday I successfully converted one ePub into AZW3 and uploaded it to my Kindle Paperwhite (12th generation), however, when I tried to open it, all pages are blank!
I tried to convert it to Mobi, the same issue as what I saw for the azw3 format!
So what is the solution if we really need the epub reading on newer Kindle devices?
Blank pages after sideloading usually mean the EPUB’s formatting is broken or the Kindle is handling that file poorly, so the most reliable next step is to test a different delivery/conversion path rather than keep re-copying the same file.
Solution 1. Send ePub to Kindle via Send2Kindle online service.
Solution 2. Convert ePub to KFX format (free) and read KFX on Kindle.
Here in this article I will introduce the later solution, because the online kindle service can only help send ePub files lower than 200MB and I did always see the sending server errors. It seems like the Amazon Kindle online service is not as stable as we think. Personally, I am inclined to believe that Kindle’s objective with this online service is to collect data on the books users upload, using this information to determine which high-selling e-books to list in their store. While this constitutes a sound competitive strategy, it is not something I personally care for; consequently, I do not recommend this approach in this article. I prefer a localized workflow—after all, my ultimate goal is simply to convert the files I have purchased into local files stored on my own device.
Step 1. Add KFX Output Plugin to Calibre.
The purpose of the KFX Output plugin is to convert e-books into KFX files that can be sideloaded to newer Kindle apps and devices. This allows books obtained from sources other than Amazon to be read with Enhanced Typesetting, multi-thumbnail Page Flip, non-justified alignment, continuous scrolling, page curl, Guided View for comics, and sticky notes (on Kindle Scribe). - jhowell
Requirement: Ensure you have installed the Kindle Previewer 3 on your laptop. It's essential. Otherwise, you will get the "KFX conversion failed" error.
Download the KFX Output plugin(version 2.19.0, last edited on April 2026) to Calibre first.
Open Calibre, then nevigate to "Preferences" -- "Plugins" -- "Load plugin from file".
Continue, select the downloaded KFX Output.zip file to finish the plugin importing.
From the pop up "Are you sure" window click "YES" to let the Calibre approve this plugin's adding.
Now the plugin is successfully added, restart Calibre to take effect.
The KFX Output plugin is installed under "Conversion output".
Step2. Convert ePub Cleanly into KFX with Calibre (free)
Drag one ePub file to Calibre library and click on "Convert books" icon.
Tips: To ensure Kindle covers to show up in our library, I highly recommend you check the "Use cover from source file".
From the output format dropdown menu select "KFX" as the target format. It might take a couple minutes.
Once it's finished, click "Book files" folder to locate the newly generated KFX format file.
Note: You can't directly open the KFX format file with calibre built-in reader.
Step 3. Transfer KFX to Newer Kindle Device via USB
Connect the Kindle device via USB cable. Then copy the .kfx format file to its local drive This PC\Kindle Paperwhite\Internal Storage\documents.
Now eject kindle device. Different from the azw3 or mobi format file, the newly copied kfx book is shown up in Kindle library and can be viewed correctly.
The Benefits of KFX
Older Kindle devices support both azw3 format and mobi format, but for modern kindle devices, the KFX format is your best choice for your sideloaded book files(deliver the best possible reading experience).
| Benefit | Mobi | AZW3 | KFX |
|---|---|---|---|
| Introduced | ~2000 | 2011 | 2015 |
| Enhanced Typesetting | / | / | Yes |
| Fixed Layout Support | / | Yes | Yes |
| Real Page Numbers | / | Partial | Yes |
| Font Embedding | / | Yes | Yes |
| File Compression | Basic | Medium | Advanced |
| CSS Support | Limited | HTML5/CSS3 | Extended |
| X-Ray/page flip Support | Partial | Partial | Full |
| Works on new Kindles(2024+) | Blocked | Blocked | Yes |
That's all. This guide is mainly for readers who want to read non-Amazon books on their newer Kindle devices with the best reading experience. Of course, there are other ways of converting book files into KFX format. If you are an author, when conver book files to KFX format with Calibre, you'd better customize the "KFX Output" features to enable "Create book EBOK instead of personal document PDOC". But this guide I won't show the details, if you are an author, visit the Amazon KDP help page for mor assistance please.
Angel Dan has covered software online marketing for more than 10 years. She joined Epubor since 2013, covering content writing, affiliate marketing, global brand expansion, video marketing, and business development.
