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MOBI to AZW3 converter

MOBI to AZW3 upgrades an old Mobipocket package to a version 8 Kindle file while leaving DRM-protected inputs unsupported.

  • 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

  • Kindle container Changed

    The fixture MOBI became a version 8 Mobipocket ebook, and BOOKMOBI remained visible at byte offset 60.

  • Text order Kept

    Our ebook engine preserved the linear reading order while rebuilding the Kindle package.

  • Legacy MOBI limits Changed

    The output cannot invent rich styling that was never present in the source MOBI file.

  • Metadata Changed

    The sample kept Unknown title metadata, showing that conversion does not repair missing catalog fields by itself.

  • Images Changed

    Images can be repackaged or recompressed during the Kindle-format rebuild.

  • DRM Lost

    Encrypted MOBI inputs remain unusable because the converter does not read or strip protected payloads.

Sample conversions

Legacy MOBI fixture

Input
11 KB sample MOBI reported as Unknown, version 6, with BOOKMOBI in the header.
Output
14,002 byte AZW3 reported as version 8; the header still contained BOOKMOBI and metadata stayed sparse.

Rich generated MOBI

Input
10,778 byte MOBI produced from the rich EPUB that had chapter headings, a table, image content, and a footnote.
Output
15,103 byte AZW3 with BOOKMOBI at byte 60, confirming our ebook engine rebuilt it as a Kindle KF8-style file.

A real MOBI → AZW3 run

We converted our MOBI sample (11 KB) with Ebook engine on 2026-09-11. It took 274 ms and produced a 14 KB AZW3 file, 1.3× larger than the input. The engine raised no warnings.

Input · sample.mobi · 11 KB

Palm database, BOOKMOBI (KF7), title “Unknown”

Identifier
BOOKMOBI
Title
Unknown

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.mobi out.azw3

Converting from MOBI improves the container, not the source quality; missing metadata and simple styling may stay simple.

MOBI 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=mobi&to=azw3.

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

When this is the wrong conversion

  • Use /convert/mobi-to-epub when the destination is Apple Books, Kobo, or another EPUB reader.
  • Use /convert/mobi-to-pdf for print review or fixed-page archiving.
  • Do not use this to process encrypted Kindle downloads.

MOBI to AZW3 questions

Is AZW3 always better than MOBI?

AZW3 supports newer Kindle rendering than old MOBI. It still cannot recreate layout, metadata, or images that were already simplified in the MOBI source.

How did you verify the AZW3 output?

Both tested outputs had BOOKMOBI at offset 60, and file identified them as Mobipocket version 8 ebooks. That matched the expected AZW3/KF8 container.

Will MOBI to AZW3 add missing title metadata?

No. The sample with Unknown title stayed sparse after conversion. Fix metadata before conversion if Kindle library sorting matters.

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