[Conversion Output] KFX Output - Page 123

Zillion_ · 10-11-2026, 06:44 AM

Hello, I have an issue trying to use :has() pseudo-class selectors in e-books.

Example:
.ChapterS:has(+.SubChapter) {
margin-bottom: 1em !important;
color: red !important;
}

The Kindle conversion logs show this:

Reading TOC from NCX...
Merging user specified metadata...
Detecting structure...
Inserting metadata into book...
Flattening CSS and remapping font sizes...
Ignoring CSS rule with invalid selector: '.ChapterS:has(+ blockquote)' (The pseudo-class :has() is unknown)
Ignoring CSS rule with invalid selector: '.ChapterS:has(+ .ChapterLocation)' (Expected an argument, got <DELIM '.' at 16>)
Ignoring CSS rule with invalid selector: '.ChapterS:has(+ .SubChapter)' (Expected an argument, got <DELIM '.' at 16>)
Ignoring CSS rule with invalid selector: '.ChapterS:has(+ blockquote)' (The pseudo-class :has() is unknown)
Ignoring CSS rule with invalid selector: '.ChapterS:has(+ .ChapterLocation)' (Expected an argument, got <DELIM '.' at 16>)
Ignoring CSS rule with invalid selector: '.ChapterS:has(+ .SubChapter)' (Expected an argument, got <DELIM '.' at 16>)
Ignoring CSS rule with invalid selector: '.ChapterS:has(+ blockquote)' (The pseudo-class :has() is unknown)

Calibre supports them correctly for the display in the editor (text displays correctly, tested with some color tags) but the conversion doesn't.
Is this an issue in Calibre or in KFX Output ? (unclear to me)

jhowell · 10-11-2026, 09:14 AM

Quote:

Originally Posted by Zillion_

Hello, I have an issue trying to use :has() pseudo-class selectors in e-books.
...
Calibre supports them correctly for the display in the editor (text displays correctly, tested with some color tags) but the conversion doesn't.
Is this an issue in Calibre or in KFX Output ? (unclear to me)

The error messages that start with "Ignoring CSS rule with invalid selector" are produced by calibre's conversion pipeline, not by this plugin. If you instead convert the same book from EPUB to AZW3 (therefore not using this plugin) you will see the same errors and will also see that calibre strips out those pseudo-classes during conversion.

Even if you avoid calibre's removal of those pseudo-classes by using the CLI of this plugin it still will not work because they are also unsupported by Amazon and will be silently discarded by Amazon's Kindle Previewer during conversion.

tomsem · 10-11-2026, 04:29 PM

Quote:

Originally Posted by jhowell

There are also numerous, serious bugs in Kindle Previewer 4 that have not yet been fixed in the three quickly released updates to it. (I guess that Alexa is just not the best choice to use when vibe coding.)

Presumably these bugs are shared by Send To Kindle? Might be interesting to compare them.

jhowell · 10-11-2026, 09:02 PM

Quote:

Originally Posted by tomsem

Presumably these bugs are shared by Send To Kindle? Might be interesting to compare them.

Most of the bugs seem to have been introduced in attempting to update to x64 MSIX in Windows and ARM in macOS. As far as I can tell the conversion done in Amazon’s servers for send-to-kindle happens under Linux and so it is not affected.

tomsem · 10-12-2026, 11:47 AM

Quote:

Originally Posted by jhowell

Most of the bugs seem to have been introduced in attempting to update to x64 MSIX in Windows and ARM in macOS. As far as I can tell the conversion done in Amazon’s servers for send-to-kindle happens under Linux and so it is not affected.

That makes sense.

The three epub books that I reported problems with upthread, with entity in alt text are passing muster with STK (as well as Kindle Previewer 4.x). They were not passing when I tried the 3 ePubs weeks ago.

jhowell · 10-12-2026, 05:28 PM

Quote:

Originally Posted by tomsem

That makes sense.

The three epub books that I reported problems with upthread, with entity in alt text are passing muster with STK (as well as Kindle Previewer 4.x). They were not passing when I tried the 3 ePubs weeks ago.

They are definitely fixing some of the conversion problems. If they would just fix the handling of SVG images I would strongly recommend upgrading to 4. As it is now it’s a toss up between 3 and 4 for the books I test with.

SASSBS · 10-21-2026, 04:39 AM

So I stupidly purchased a new Alexa Tablet as I needed a new Kindle.

I created a Kindle and Books folders in root, placed a test KFX book there and nothing shows in Kindle app.

Checked that the local access is set for both folders rebooted the Tablet no change.

Formatted and setup fresh still not showing.

Thanks
Has anyone got any ideas on what else I can try?

JSWolf · 10-21-2026, 04:45 AM

Quote:

Originally Posted by SASSBS

So I stupidly purchased a new Alexa Tablet as I needed a new Kindle.

I created a Kindle and Books folders in root, placed a test KFX book there and nothing shows in Kindle app.

Checked that the local access is set for both folders rebooted the Tablet no change.

Formatted and setup fresh still not showing.

Thanks
Has anyone got any ideas on what else I can try?

Using the Kindle app on the tablet, where is it that the app places downloaded eBooks from Amazon?

SASSBS · 10-21-2026, 04:47 AM

I assume in the hidden android data .com folder but it's locked down and you can't access it at all.

JSWolf · 10-21-2026, 08:42 AM

Quote:

Originally Posted by SASSBS

I assume in the hidden android data .com folder but it's locked down and you can't access it at all.

Can you jailbreak?

SASSBS · 10-21-2026, 08:51 AM

Don't believe there are any yet, I am going to return it. Too many issues you can't send books from my content page to it, and transferring 1000 books took 3 hours and I still have 3500 to go.
Shame as having Play store was nice

jhowell · 10-21-2026, 05:03 PM

Quote:

Originally Posted by SASSBS

So I stupidly purchased a new Alexa Tablet as I needed a new Kindle.
...
Has anyone got any ideas on what else I can try?

From what I have read I assume that an Alexa Tablet should function more or less like a regular Android device.

The folder in which the Kindle for Android app stores books is accessible via MTP as /Android/data/com.amazon.kindle/files. Placing a KFX book file into that folder should cause it to appear in the Kindle app.

SASSBS · 10-22-2026, 02:08 AM

yeah I returned it for now, it's a shame if you can't sideload books without plugging it into a PC it's not ideal for me, though Amazon will think it's great I am sure.

Between the slowness of getting books on and the fact that I couldn't send bought books from the My Content and Devices to it along with the poor home screen design it's just not worth it at the moment.

10-11-2026, 06:44 AM	#1831
Zillion_ Enthusiast Posts: 40 Karma: 10 Join Date: Jul 2023 Device: Kindle ColorSoft	Using :has() Hello, I have an issue trying to use :has() pseudo-class selectors in e-books. Example: .ChapterS:has(+.SubChapter) { margin-bottom: 1em !important; color: red !important; } The Kindle conversion logs show this: Reading TOC from NCX... Merging user specified metadata... Detecting structure... Inserting metadata into book... Flattening CSS and remapping font sizes... Ignoring CSS rule with invalid selector: '.ChapterS:has(+ blockquote)' (The pseudo-class :has() is unknown) Ignoring CSS rule with invalid selector: '.ChapterS:has(+ .ChapterLocation)' (Expected an argument, got <DELIM '.' at 16>) Ignoring CSS rule with invalid selector: '.ChapterS:has(+ .SubChapter)' (Expected an argument, got <DELIM '.' at 16>) Ignoring CSS rule with invalid selector: '.ChapterS:has(+ blockquote)' (The pseudo-class :has() is unknown) Ignoring CSS rule with invalid selector: '.ChapterS:has(+ .ChapterLocation)' (Expected an argument, got <DELIM '.' at 16>) Ignoring CSS rule with invalid selector: '.ChapterS:has(+ .SubChapter)' (Expected an argument, got <DELIM '.' at 16>) Ignoring CSS rule with invalid selector: '.ChapterS:has(+ blockquote)' (The pseudo-class :has() is unknown) Calibre supports them correctly for the display in the editor (text displays correctly, tested with some color tags) but the conversion doesn't. Is this an issue in Calibre or in KFX Output ? (unclear to me)

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10-21-2026, 04:39 AM	#1837
SASSBS Zealot Posts: 105 Karma: 118 Join Date: Aug 2011 Device: Kindle Keyboard; Kindle Fire	So I stupidly purchased a new Alexa Tablet as I needed a new Kindle. I created a Kindle and Books folders in root, placed a test KFX book there and nothing shows in Kindle app. Checked that the local access is set for both folders rebooted the Tablet no change. Formatted and setup fresh still not showing. Thanks Has anyone got any ideas on what else I can try?

10-21-2026, 04:47 AM	#1839
SASSBS Zealot Posts: 105 Karma: 118 Join Date: Aug 2011 Device: Kindle Keyboard; Kindle Fire	I assume in the hidden android data .com folder but it's locked down and you can't access it at all.

10-21-2026, 08:51 AM	#1841
SASSBS Zealot Posts: 105 Karma: 118 Join Date: Aug 2011 Device: Kindle Keyboard; Kindle Fire	Don't believe there are any yet, I am going to return it. Too many issues you can't send books from my content page to it, and transferring 1000 books took 3 hours and I still have 3500 to go. Shame as having Play store was nice

10-22-2026, 02:08 AM	#1843
SASSBS Zealot Posts: 105 Karma: 118 Join Date: Aug 2011 Device: Kindle Keyboard; Kindle Fire	yeah I returned it for now, it's a shame if you can't sideload books without plugging it into a PC it's not ideal for me, though Amazon will think it's great I am sure. Between the slowness of getting books on and the fact that I couldn't send bought books from the My Content and Devices to it along with the poor home screen design it's just not worth it at the moment.