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EPUB to AZW3 Converter
Convert EPUB to Kindle’s AZW3 format for sideloading. Runs entirely on your device.
Files never uploaded Works offline Free, no signup No file size limits
How it works
- Drop your EPUB into the box above.
- Chapters, images, styles and the table of contents are repacked into Kindle’s KF8 container.
- Copy the .azw3 to your Kindle over USB and it appears in your library.
Why “no upload” matters
Every conventional converter site works the same way: your file travels to their server, sits in their queue, gets converted on their hardware, and – you hope – gets deleted afterwards. You can’t verify any of it. The FBI has even warned about free converter sites that use that upload as a way to deliver malware or harvest the documents themselves. Your books are yours; a format change shouldn’t require handing them to a stranger.
ebook.tools removes the question entirely. The converter is delivered to your browser as code and runs on your machine; the file you drop is opened from memory, transformed, and saved back – the network isn’t involved at all. That isn’t a policy promise, it’s an architecture, and you can test it: load this page, switch off your wifi, and convert. It works exactly the same, because there was never anything to send.
When AZW3 is the right choice – and when it isn’t
Modern Kindle and internet handy? Send to Kindle with EPUB is usually the better route – books sync position and appear in your Amazon library. Run yours through the fixer first. AZW3 shines where that route doesn't reach.
AZW3 – Kindle Format 8 – is what Kindles have natively spoken since 2011, and there are three genuinely good reasons to convert to it. Sideloading by USB: a Paperwhite-era Kindle takes an AZW3 by drag-and-drop with no Amazon account, no wifi and no email loop involved. Kindles that predate EPUB support: a decade of models accept AZW3 over USB but never learned to ingest EPUB directly. Staying off the cloud: Send to Kindle uploads your book to Amazon's servers by design; a USB sideload keeps a private manuscript entirely between you and your device.
Because KF8 is built on the same HTML-and-CSS foundations as EPUB, this is the highest-fidelity Kindle conversion: your chapter structure, stylesheets, images and table of contents are repacked rather than flattened, and the on-device TOC and in-book navigation work as Kindle expects. Under the hood the converter builds the real KF8 structures – the skeleton and fragment indexes, flow table and NCX navigation index – the same binary anatomy Amazon's own kindlegen produced.
The honest bits: as with everything here, DRM-protected input is detected and declined, and this converter is new – output is verified against the same KF8 parser the Foliate reader uses, and we test on real hardware before each release, but if a particular book misbehaves on your Kindle we genuinely want to hear about it. Converting the other direction? AZW3 to EPUB is over here.