Book Batcher

AZW3 → MOBI

AZW3 to MOBI

For a Kindle or an app that predates Kindle Format 8. The book is read from its AZW3 structure — with the chapter divisions it was written with — and written out as a MOBI with a contents list that lands where it should.

No upload · Files are read in this tab and never sent anywhere

Intake

Drop AZW3 files here

.azw3 and .kf8, as many as you like. A combination file holding both an old MOBI and a KF8 version is read from its newer half.

Output format

MOBI — The older Kindle format for compatible devices via USB, with limited styling.

What survives

  • The chapters as the book was authored, taken from the KF8 document boundaries.
  • Title, authors, publisher, subjects, description and identifiers.
  • Every image, with the cover marked so the Kindle library shows it.
  • A working table of contents, with links measured after the book is laid out.

What does not

  • The book’s stylesheet and embedded fonts, which MOBI cannot carry.
  • Kindle-internal kindle:pos: links, which point into positions in the original file.
  • Fixed layout. MOBI always reflows, so comics belong in PDF.

Going to anything other than a Kindle?

Convert to EPUB instead — AZW3 to EPUB keeps more of the book, and every other reader opens it. Sending to a Kindle by email or app? Read how to put an EPUB on a Kindle first.

Questions

Why convert AZW3 to MOBI at all?
Older Kindle models and some reading apps open MOBI but not AZW3 (Kindle Format 8). Converting gives those devices a file they can read. If your device already opens the AZW3, keep the AZW3: it carries the book’s own stylesheet, and MOBI cannot.
What is lost in the conversion?
The typography. MOBI has no support for stylesheets or embedded fonts, so the book is shown in the device’s own type. The text, chapters, images, cover, metadata and contents list are kept, and the conversion says on the file what it changed.
Can it convert a Kindle book I bought from Amazon?
Not if it is protected by DRM, which most purchased Kindle books are. Protection is detected from the file header and the book is refused with an explanation. Nothing here removes DRM.
Is my book uploaded anywhere?
No. The file is read and converted inside this browser tab, in a background thread, and saved with the browser’s own download. The page’s security policy blocks connections to any other server.