Skip to content

EPUB to AZW3 converter

EPUB to AZW3 runs through our ebook engine, and our rich EPUB became a KF8 Mobipocket file with BOOKMOBI bytes at offset 60.

  • Converted with Ebook engine · input deleted within 24 h
  • Free: 5 conversions a day · 5 MB each
  • Higher limits →

From real runs

What you get — and what changes

  • DRM Lost

    Encrypted bookstore files fail before conversion; this route does not decrypt Kindle or EPUB protection.

  • Chapter order Kept

    The two rich-fixture chapters survived the AZW3 pass and reappeared in the round-tripped EPUB table of contents.

  • Navigation package Changed

    The EPUB 3 nav document was not present after AZW3 round-trip, while our ebook engine rebuilt an NCX navigation file.

  • Images Changed

    The embedded PNG survived, but our ebook engine added a separate JPEG cover item during the AZW3 to EPUB return leg.

  • Metadata Kept

    The rich fixture kept title Rich QA EPUB and creator FTC Writer QA through AZW3 and back to EPUB.

  • Tables Changed

    The two-row Markdown table remained readable, but Kindle packaging no longer looked like the source EPUB XHTML.

Sample conversions

API-built EPUB with table and footnote

Input
6,121 byte EPUB made from Markdown by the API, with two chapters, a footnote, one embedded PNG, OPF title and creator, nav.xhtml, and toc.ncx.
Output
14,585 byte AZW3 whose header contained BOOKMOBI at byte 60; after AZW3 to EPUB, NCX labels still listed Chapter One and Chapter Two.

Feedback Atlas sample EPUB

Input
5.4 KB fixture EPUB with one report chapter, Q2 and Q3 table values, bullets, and no dc:title value in the OPF.
Output
14,757 byte AZW3 with a Mobipocket header; the source's missing title metadata meant Kindle metadata was less useful than the visible heading.

A real EPUB → AZW3 run

We converted our EPUB sample (5 KB) with Ebook engine on 2026-09-11. It took 377 ms and produced a 14 KB AZW3 file, 2.7× larger than the input. The engine raised no warnings.

Input · sample.epub · 5 KB

EPUB 3.0: 3 content documents, 0 images, EPUB 3 nav, no cover

Version
3.0
Content documents
3
Images
0
Table of contents
EPUB 3 nav
Cover
no cover

Output · sample.azw3 · 14 KB

Palm database, BOOKMOBI (KF8), title “Unknown”

Identifier
BOOKMOBI
Title
Unknown

Do it yourself

Calibre ebook-convert

bash
ebook-convert in.epub out.azw3

Only use this on files you are allowed to convert. Calibre does not remove DRM, and AZW3 is mainly for Kindle sideloading.

EPUB to AZW3 by API or MCP

The HTTP API and the MCP server run the exact engine this page uses (Ebook engine); the response carries the same warnings the web converter shows. Check support first with GET /api/v1/pairs?from=epub&to=azw3.

curl
curl -X POST https://filetypeconverters.com/api/v1/convert \
  -H "Authorization: Bearer $FTC_API_KEY" \
  -F "file=@input.epub" -F "from=epub" -F "to=azw3" \
  --output output.azw3
API reference

When this is the wrong conversion

  • Use /convert/epub-to-pdf when the recipient needs printable pages rather than a reflowable Kindle package.
  • Use /convert/epub-to-md when the goal is to edit chapter text in a repository instead of reading on Kindle.
  • Do not convert only to bypass a store restriction; protected purchases will fail here.

EPUB to AZW3 questions

How can I tell the EPUB became a real AZW3 file?

In our run, the output was identified as a Mobipocket ebook, version 8, and the bytes at offset 60 spelled BOOKMOBI. That is the header signature we checked before writing this entry.

Does EPUB navigation survive in AZW3?

Chapter navigation survived, but not as the same EPUB files. The round-trip back to EPUB had toc.ncx entries for the chapters and no nav.xhtml file.

Will this handle DRM-protected EPUB books?

No. Protected files are rejected or fail to open, and nothing in this converter removes DRM. Use an unencrypted personal document or publisher-provided export.

Related conversions