[Conversion Plugin] KFX Input - Page 82

jhowell · 05-20-2026, 02:18 PM

Version 2.33.0 - 20 May 2026

Handle new variant of KFX comic format. (Fixes "BookPart filename xxx is not unique")

Dragonqueen · 05-21-2026, 02:25 AM

KFX is now being transferred from the device as a KFX ZIP file again.
I suspect a new KFX version.
I'm using Calibre 9.8, DeDRM 10.0.9, KFX Input 2.33.0 & the serial number is stored

The error is: Conversion not possible
This book is locked by DRM

JSWolf · 05-21-2026, 08:29 AM

Quote:

Originally Posted by Dragonqueen

KFX is now being transferred from the device as a KFX ZIP file again.
I suspect a new KFX version.
I'm using Calibre 9.8, DeDRM 10.0.9, KFX Input 2.33.0 & the serial number is stored

The error is: Conversion not possible
This book is locked by DRM

Your Kindle was updated by Amazon to change the DRM used by KFX.

jhowell · 05-21-2026, 10:33 AM

Quote:

Originally Posted by Dragonqueen

KFX is now being transferred from the device as a KFX ZIP file again.
I suspect a new KFX version.
I'm using Calibre 9.8, DeDRM 10.0.9, KFX Input 2.33.0 & the serial number is stored

The error is: Conversion not possible
This book is locked by DRM

Amazon has recently updated the DRM in use on almost all Kindle devices, even older ones that have not received a full firmware update in years. The first post in the thread Dealing with Kindle ebooks in calibre generally has the latest information on the status of Kindle DRM.

kkkkkk · 06-16-2026, 02:24 AM

When I open an EPUB converted from KFX using Sigil, the following warning pops up:

"Warning: This EPUB had HTML files that were not well formed or are missing a DOCTYPE, html, head or body elements."

I noticed that the XHTML files are missing the modern web standard <!DOCTYPE html>.

In kfxlib/epub_output.py, around lines 550 to 570, near the end of the save_book_parts function, the original code is:

Original code:

Code:

if not self.generate_epub2:
    html_str = html_str.replace(doctype + b"\n", b"")

To fix this for EPUB 3, I suggest modifying it like this:

Suggested modification:

Code:

if not self.generate_epub2:
    html_str = html_str.replace(doctype + b"\n", b"<!DOCTYPE html>\n")

This simple change ensures that the generated EPUB 3 files include the proper DOCTYPE declaration and resolves the Sigil warning.

Additionally, I would like to know what the reason is for setting PLACE_FILES_IN_SUBDIRS = False to disable the categorized resource folder structure?

jhowell · 06-16-2026, 10:21 AM

Quote:

Originally Posted by kkkkkk

When I open an EPUB converted from KFX using Sigil, the following warning pops up:

"Warning: This EPUB had HTML files that were not well formed or are missing a DOCTYPE, html, head or body elements."

I noticed that the XHTML files are missing the modern web standard <!DOCTYPE html>.

DOCTYPE is optional in EPUB 3, but since it does not hurt to include it I will change the plugin to do so in the next release.

Quote:

Originally Posted by kkkkkk

Additionally, I would like to know what the reason is for setting PLACE_FILES_IN_SUBDIRS = False to disable the categorized resource folder structure?

There were occasional problems with the linkages between files for some books when they were placed in separate folders. Since there is no technical advantage to separating them it was easiest to resolve that by just keeping them together.

yoshi · 06-18-2026, 08:35 AM

We were able to download almost all books published before April 23, 2025 as AZW3 files using the old version of "Kindle for PC" in Japan.

I recently downloaded a comic book as AZW3 and then downloaded the same title again as KFX using the new Kindle app. I converted the AZW3 file to EPUB with "KindleUnpack" and the KFX file to EPUB with "From KFX". I compared the two "content.opf" files. In the AZW3 version, the cover page has the property "page-spread-center", but this property is missing in the KFX version.

Is it impossible to retrieve this information from KFX?

I uploaded two files.

jhowell · 06-18-2026, 10:10 AM

Quote:

Originally Posted by yoshi

I recently downloaded a comic book as AZW3 and then downloaded the same title again as KFX using the new Kindle app. I converted the AZW3 file to EPUB with "KindleUnpack" and the KFX file to EPUB with "From KFX". I compared the two "content.opf" files. In the AZW3 version, the cover page has the property "page-spread-center", but this property is missing in the KFX version.

Is it impossible to retrieve this information from KFX?

That property is not present in comics in KFX format.

There is an option to have this plugin add it during conversion to EPUB. See the section "Plugin Tweaks" under "Configuration" in the first post of this thread for more information.

yoshi · 06-18-2026, 08:13 PM

Thank you for your reply.
"page-spread-center" was added.

yoshi · 06-23-2026, 05:19 AM

May I ask you a question?

Does the Kindle app treat the cover page as centered by default, even without the page-spread-center property?

And is that why Amazon doesn't include it in KFX?

bustacap · 06-23-2026, 05:54 AM

Quote:

Originally Posted by yoshi

May I ask you a question?

Does the Kindle app treat the cover page as centered by default, even without the page-spread-center property?

And is that why Amazon doesn't include it in KFX?

its definitely not needed. even if there are epub readers that dont center it, they (should) always display the first page alone (next to a blank page if not centered)

yoshi · 06-23-2026, 10:01 AM

I understand that an EPUB produced from an AZW3 file is generally close to the publisher's original data.

As I wrote earlier, I noticed that the EPUB converted from the AZW3 edition of the same book contains the page-spread-center property. I'm curious why this property does not appear in KFX.

For EPUB files, some reading systems do not center the cover page when page-spread-center is not specified.

jhowell · 06-23-2026, 10:15 AM

Quote:

Originally Posted by yoshi

Does the Kindle app treat the cover page as centered by default, even without the page-spread-center property?

Yes.

Quote:

Originally Posted by yoshi

And is that why Amazon doesn't include it in KFX?

Amazon's KFX format is only loosely based on EPUB and HTML. It has its own unique way of representing double page spreads which is not an exact equivalent of the EPUB page-spread properties. Basically in a KFX comic, a "section" has either two pages (rendered either left-and-right or right-and-left based on the page progression direction) or a single page (rendered centered). The related properties that appear in the converted EPUB are added by this plugin.

Upon reflection it appears that it would be best to always add "rendition:page-spread-center" in the single page case to better match how Kindles display them. I will change this in the next plugin release.

yoshi · 06-23-2026, 08:59 PM

Thank you for your explanation.

Adding "rendition:page-spread-center" without using "Plugin Tweaks" would be beneficial for EPUB readers.

yoshi · 06-23-2026, 09:10 PM

I tried to correct the above corrupted character but failed to do it.

06-16-2026, 02:24 AM	#1220
kkkkkk Junior Member Posts: 2 Karma: 10 Join Date: Jun 2026 Device: none	When I open an EPUB converted from KFX using Sigil, the following warning pops up: "Warning: This EPUB had HTML files that were not well formed or are missing a DOCTYPE, html, head or body elements." I noticed that the XHTML files are missing the modern web standard <!DOCTYPE html>. In kfxlib/epub_output.py, around lines 550 to 570, near the end of the save_book_parts function, the original code is: Original code: Code: if not self.generate_epub2: html_str = html_str.replace(doctype + b"\n", b"") To fix this for EPUB 3, I suggest modifying it like this: Suggested modification: Code: if not self.generate_epub2: html_str = html_str.replace(doctype + b"\n", b"<!DOCTYPE html>\n") This simple change ensures that the generated EPUB 3 files include the proper DOCTYPE declaration and resolves the Sigil warning. Additionally, I would like to know what the reason is for setting PLACE_FILES_IN_SUBDIRS = False to disable the categorized resource folder structure?

06-23-2026, 08:59 PM	#1229
yoshi Enthusiast Posts: 33 Karma: 10 Join Date: Aug 2024 Location: Japan Device: Kindle (2024), Kindle Voyage & Kindle for Windows	Thank you for your explanation. Adding "rendition:page-spread-center" without using "Plugin Tweaks" would be beneficial for EPUB readers. Last edited by theducks; 06-23-2026 at 09:56 PM. Reason: Character corruption

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05-20-2026, 02:18 PM	#1216
jhowell Grand Sorcerer Posts: 7,383 Karma: 95902893 Join Date: Nov 2011 Location: Charlottesville, VA Device: Kindles	Version 2.33.0 - 20 May 2026 Handle new variant of KFX comic format. (Fixes "BookPart filename xxx is not unique")

05-21-2026, 02:25 AM	#1217
Dragonqueen Junior Member Posts: 1 Karma: 10 Join Date: May 2026 Device: Kindle, Pocketbook P741, Android	KFX is now being transferred from the device as a KFX ZIP file again. I suspect a new KFX version. I'm using Calibre 9.8, DeDRM 10.0.9, KFX Input 2.33.0 & the serial number is stored The error is: Conversion not possible This book is locked by DRM

06-18-2026, 08:35 AM	#1222
yoshi Enthusiast Posts: 33 Karma: 10 Join Date: Aug 2024 Location: Japan Device: Kindle (2024), Kindle Voyage & Kindle for Windows	We were able to download almost all books published before April 23, 2025 as AZW3 files using the old version of "Kindle for PC" in Japan. I recently downloaded a comic book as AZW3 and then downloaded the same title again as KFX using the new Kindle app. I converted the AZW3 file to EPUB with "KindleUnpack" and the KFX file to EPUB with "From KFX". I compared the two "content.opf" files. In the AZW3 version, the cover page has the property "page-spread-center", but this property is missing in the KFX version. Is it impossible to retrieve this information from KFX? I uploaded two files.

06-18-2026, 08:13 PM	#1224
yoshi Enthusiast Posts: 33 Karma: 10 Join Date: Aug 2024 Location: Japan Device: Kindle (2024), Kindle Voyage & Kindle for Windows	Thank you for your reply. "page-spread-center" was added.

06-23-2026, 05:19 AM	#1225
yoshi Enthusiast Posts: 33 Karma: 10 Join Date: Aug 2024 Location: Japan Device: Kindle (2024), Kindle Voyage & Kindle for Windows	May I ask you a question? Does the Kindle app treat the cover page as centered by default, even without the page-spread-center property? And is that why Amazon doesn't include it in KFX?

06-23-2026, 10:01 AM	#1227
yoshi Enthusiast Posts: 33 Karma: 10 Join Date: Aug 2024 Location: Japan Device: Kindle (2024), Kindle Voyage & Kindle for Windows	I understand that an EPUB produced from an AZW3 file is generally close to the publisher's original data. As I wrote earlier, I noticed that the EPUB converted from the AZW3 edition of the same book contains the page-spread-center property. I'm curious why this property does not appear in KFX. For EPUB files, some reading systems do not center the cover page when page-spread-center is not specified.

06-23-2026, 09:10 PM	#1230
yoshi Enthusiast Posts: 33 Karma: 10 Join Date: Aug 2024 Location: Japan Device: Kindle (2024), Kindle Voyage & Kindle for Windows	I tried to correct the above corrupted character but failed to do it.