Everything you need to know about AZW3
AZW3 (.azw3, also Kindle Format 8 / KF8) is Amazon's modern Kindle ebook format, introduced in 2011. It replaced MOBI as the default Kindle format and brought EPUB-3 level features: embedded fonts, advanced typography, fixed-layout support for comics and children's books, and HTML5/CSS3 capabilities.
How it works under the hood
- HTML5/CSS3 inside. Like EPUB 3, AZW3 uses modern web standards for content - clean separation of structure (HTML) and styling (CSS).
- Embedded fonts. AZW3 supports custom fonts (TTF/OTF), unlike MOBI - critical for non-Latin scripts and design-heavy books.
- Fixed-layout support. For comics, children's books, and cookbooks where layout matters more than reflow.
- Amazon DRM (optional). Books from the Kindle store have AZW DRM; self-published or library AZW3 may not.
Where you'll actually use it
- Modern Kindle devices (2011 onwards)
- Kindle apps (iOS, Android, Mac, Windows)
- Amazon KDP self-publishing (Amazon converts EPUB upload to AZW3 internally)
- Books with custom typography or fixed layout
How it compares to alternatives
AZW3 vs EPUB: AZW3 is Kindle-specific; EPUB is universal. They have similar capabilities. AZW3 vs MOBI: AZW3 replaced MOBI - better typography, embedded fonts, more features.
Things that will trip you up
- AZW3 with Amazon DRM only works on Amazon-registered devices and apps
- Older Kindles (pre-2011) cannot read AZW3 - send MOBI to legacy devices
- Calibre's AZW3 conversion is reliable; sideloading converted files works for personal libraries
Test it yourself: Calibre (free, best AZW3 tool), Amazon's Kindle Previewer (free, official), Kindle apps for cross-device testing.