Markdown/DOCX → MOBI/AZW3

What is Markdown/DOCX?

Markdown (.md) and Word documents (.docx) are grouped here because they play the same role in conversion: lightweight structured authoring sources. Markdown is plain text plus markers (# headings, ** bold) — clean but limited. A .docx is a ZIP of Office Open XML with far richer layout (pagination, headers, footers, comments, tracked changes). Both are good conversion sources rather than final reading formats.

What is MOBI/AZW3?

Mobipocket (.mobi) was long the default format Amazon accepted for Kindle delivery. AZW3 (also called KF8) is its successor with fuller HTML5/CSS support, and .azw is an earlier Amazon container. All three reflow and carry navigation and metadata, so they behave as one family. They are proprietary to Amazon's ecosystem, and since 2022 Amazon sends KFX/EPUB instead, so .mobi is mostly a legacy format now.

What to watch out for when converting Markdown/DOCX to MOBI/AZW3

Extracting from the source

A .docx is a ZIP of Office Open XML with content in word/document.xml. Heading styles decide whether chapters survive: if the author used manually-bolded large text instead of Heading 1, the resulting EPUB has no table of contents. Markdown, by contrast, cannot express complex tables or deep nesting.

Writing the target format

Producing .mobi/.azw3 requires Amazon's toolchain or Calibre. AZW3 supports reasonable CSS while legacy .mobi supports very little; for newer devices, target AZW3 — or simply deliver an EPUB.

Where the two formats interact

• Chapter headings in the source are ordinary lines while the target demands a real table of contents. Converters try to match patterns such as "Chapter N"; when the match is poor the TOC is garbled or the book has a single chapter. Check that TOC entries match the actual chapter count.

Post-conversion checklist

1. Convert the first three chapters as a trial and check for lost text, interleaved lines or misplaced blocks before doing the whole book.
2. Check chapter splitting: the TOC entry count should match the real chapter count.
3. Jump to five random spots and search a character name to confirm the text is fully searchable.
4. Confirm illustration count and placement — check that images are not all dumped at the end of a chapter.
5. Fill in title, author and language — a wrong language tag breaks typesetting such as Chinese line breaking.

Converting novels: what is different

Fiction is the most common and the most peculiar kind of e-book: hundreds or thousands of chapters, almost no figures, often nothing but a TXT source, and Chinese sources that frequently carry anti-piracy garbling. These are the points that bite hardest.

• A long novel can run to hundreds or thousands of chapters, so the table of contents decides whether the result is usable. Normalise chapter headings to one recognisable pattern first — say "Chapter N Title" alone on its own line — or the target will miss chapters, merge them, or collapse the whole book into one.
• Volume markers ("Volume One", "Volume Two") usually degrade to ordinary headings, losing the volume/chapter hierarchy. If that matters, promote volume headings one level in an editor afterwards so they are not siblings of chapter titles.

Tools for converting Markdown/DOCX to MOBI/AZW3

Any of the tools below can handle this direction; pick one by your operating system and how many files you have. Read the previous section first — doing the steps out of order (converting a scanned file before running OCR, for instance) usually means starting over.

Common questions

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