Kindle File Format is a
proprietary e-book file format created by
Amazon.com that can be downloaded and read on devices like
smartphones
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating system
A ...
,
tablets,
computers, or
e-readers that have Amazon's
Kindle app. E-book files in the Kindle File Format originally had the
filename extension .azw; version 8 (KF8) introduced HTML5 & CSS3 features and have the
.azw3 extension, and version 10 introduced a new typesetting and layout engine featuring hyphens, kerning, & ligatures and have the
.kfx extension.
History
Kindle devices and apps are designed to use Amazon's e-book formats: AZW that is based on
Mobipocket; in fourth generation and later Kindles, AZW3, also called KF8; and in seventh generation and later Kindles, KFX. Kindles now support the
EPUB file format used by many other e-book readers. Similar to EPUB, Amazon's file formats are intended for
reflowable, richly formatted e-book content and support
DRM restrictions, but unlike EPUB, they are
proprietary formats. AZW files debuted with the first Amazon Kindle in 2007.
Software such as the
free and open source Calibre, Amazon's ''KindleGen'', and the email based Send-to-Kindle service are available to convert e-books into supported Kindle file formats. Kindle devices can also display some generic document formats such as
plain text
In computing, plain text is a loose term for data (e.g. file contents) that represent only characters of readable material but not its graphical representation nor other objects ( floating-point numbers, images, etc.). It may also include a li ...
(TXT) and
Portable Document Format
Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating sys ...
(PDF) files; however,
reflowing is not supported for these file types.
In late 2011, the Kindle Fire introduced "Kindle Format 8" (KF8), also known as AZW3 file format. AZW3 supports a subset of
HTML5 and
CSS3 features, while acting as a container for a backwards-compatible
MOBI content document.
["Amazon Throws A Minor Curveball With HTML5-Powered Kindle Format 8"]
TechCrunch, October 20, 2011.
In August 2015, all the Kindle e-readers released within the previous two years were updated with a new typesetting and layout engine that adds
hyphens,
kerning
In typography, kerning is the process of adjusting the spacing between characters in a proportional font, usually to achieve a visually pleasing result. Kerning adjusts the space between individual letterforms, while tracking (letter-sp ...
and
ligatures to the text; e-books that support this engine require the use of the "Kindle Format 10" (KFX) file format. E-books that support the enhanced typesetting format are indicated in the e-book's description on its product page.
In 2017, Amazon released Kindle Create, a tool that can convert Microsoft Word files to Kindle file format.
In 2022, while the
Send-to-Kindle service only supported the original .mobi/.azw ebook formats (along with some other non-ebook file formats),
Amazon announced removing this support in favor of
.epub which will be converted to Amazon's KF8 (.azw3) from late-2022.
References
{{Ebooks
Amazon (company)
Computer file formats
Electronic paper technology
Ebooks