Compile to MOBI uses wrong CSS, breaks on Kindle Fire

Hi there -

I’ve had a weird issue when viewing Scrivener-compiled MOBI files on a Kindle Fire - all the bold text is unbolded. I contacted Amazon Support, and they asked for a sample MOBI, which I sent them. Their repsonse was:

[i]"Hello From Kindle Publishing Team,
We have looked over your content, to make the content bold, you are using the CSS style “font-weight:600”. Please change this style to “font-weight:bold”. This is the recommended CSS style to make the content bold.

Best regards,

Kindle Publishing Team"[/i]

Is it possible to configure Scrivener to set how it creates MOBIs? Or is this hard-coded?


Hmm. Possible workaround, but another problem.

Calibre has a ‘Tweak Book’ function, which can ‘explode’ an e-book into the component files which you can then edit, in my case changing the font-weight setting. Then you just hit the ‘Rebuild’ button and it pulls it back together into a single MOBI file.


When I explode one of my Scrivener created MOBI files I’m told: ‘This MOBI file contains KF8 and older Mobi6 data. Tweaking it will remove the Mobi6 data, which means the file will not be usable on older Kindles.’

Which isn’t much use - and lo and behold, the recreated MOBI does indeed look terrible on the Kindle Previewer for old-style Kindles.

Second Scrivener question: is there a way to compile MOBI files from Scrivener without KF8 data? I haven’t got anything fancy in my book, so I can’t think what the KF8 stuff is…


KF8 will be, as far as I understand, the format that Amazon is transitioning to over time, so it only makes sense to start using it. In fact, the result you get it out of Scrivener isn’t really Scrivener at all, but Amazon’s own KindleGen software. All we are doing is giving it an ePub file. This would also be why, I suspect anyway, Calibre’s rebuild option simply asks if you want to discard the old version rather than give you a choice between the two.

But another trick you can use is .epub, which has more editors available for it (I like Sigil). Once you are done with that, just open the .epub in KindlePreviewer to automatically convert it to .mobi.

Ah, OK. I’ll give that a whirl. Thanks Amber!

That was so easy!

  • Compile to ePub in Scrivener
  • Open in Sigil
  • Find/replace font-weight:600 with font-weight:bold in all HTML files
  • Save ePub
  • Open in Kindle Previewer, creates MOBI

Took two minutes! I haven’t actually tested the new MOBI on a Kindle Fire yet (my fiancee’s taken it to work), so I don’t know for sure if the original lost-boldness problem is fixed, but I’m hopeful.

Thanks again, Karen.

Yup! It’s not bad, and it’s a good trick to know if you want to tweak the ToC or anything else. I’ve made a note to check up on the best way to describe font weight, though. It might be we’re not doing the best thing by using numeric values.

Thanks, it would save some (minimal) effort if I could get a clean MOBI direct from Scrivener.