AZW to EPUB is a conversion problem that starts with a decision Amazon made deliberately: Kindle devices and apps do not read EPUB, the open ebook standard used by every other major platform, and non-Kindle e-readers do not read AZW, Amazon's own format. AZW was introduced alongside the first Kindle in 2007 as a lightly modified version of the older MOBI/PalmDOC format, tagged with Amazon's own header so its DRM scheme could hook into it. AZW3, sometimes called KF8 (Kindle Format 8), arrived in 2011 to support the richer HTML5 and CSS3 layout that modern Kindle books, comics, and textbooks need — think fixed-layout picture books or magazines with multi-column text, neither of which the older MOBI-based AZW could represent well. Both formats remain closed: Amazon has never published a full specification, and no browser ships a JavaScript decoder for either one, which is precisely why this page can't offer a drag-and-drop conversion the way an image or Word-document tool can.
EPUB, the format you're converting to, is a completely different animal architecturally, even though the underlying idea — HTML and CSS wrapped in a ZIP container — is shared with AZW3/KF8. EPUB is maintained by the W3C as an open, patent-free standard, which is exactly why Apple Books, Kobo, Google Play Books, Nook, Adobe Digital Editions, and virtually every ebook app apart from Kindle can open it without licensing anything from anyone. That openness is also why EPUB has stayed remarkably stable since its 2011 (EPUB 3) revision, while Kindle formats have quietly evolved multiple times to suit Amazon's own hardware and storefront needs.
The practical reason people land on this page is almost always one of three things: they bought a DRM-free AZW file directly from a publisher and want to read it on a non-Kindle device, they're migrating a personal library after switching from a Kindle to a Kobo or an Android tablet, or they have an old personal document (a manuscript, a scanned book, a research PDF) that was "sent to Kindle" years ago and now only exists as an AZW file on an aging device. In every one of those cases, the honest answer is that browser-based conversion isn't possible today, and the free, reliable answer is Calibre — the open-source ebook management application that has handled this exact conversion since long before EPUB 3 existed.
It's worth being direct about the one thing this page can't help with: DRM. The overwhelming majority of Kindle books purchased through the Amazon store are wrapped in Amazon's DRM scheme, which encrypts the file so that only an authorized Kindle app or device — tied to your Amazon account — can decrypt and display it. That encryption is a deliberate legal and technical barrier, and stripping it (even from a book you paid for) sits in a legal grey zone in most countries and violates Amazon's terms of service everywhere. Calibre, run by itself, cannot and will not remove that encryption; it only converts files that are already DRM-free, such as personal documents, publisher-provided review copies, or ebooks bought from DRM-free retailers like Baen Books, Tor/Forge, or Smashwords-distributed titles that happen to be saved in Kindle format.
