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 mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as mult ...

, tablets,

computers A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations ('' computation''). Modern digital electronic computers can perform generic sets of operations known as ''programs'', ...

, or

e-reader An e-reader, also called an e reader or e device, is a Mobile computing, mobile electronic device that is designed primarily for the purpose of reading digital e-books and Periodical literature, periodicals. Any device that can display text on ...

s that have Amazon's Kindle app.

E-book An ebook (short for electronic book), also spelled as e-book or eBook, is a book publication made available in electronic form, consisting of text, images, or both, readable on the flat-panel display of computers or other electronic devices. Al ...

files in the Kindle File Format originally had the

filename extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (for example, .txt, .mp3, .exe) that indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...

.azw; version 8 (KF8) introduced

HTML5 HTML5 (Hypertext Markup Language 5) is a markup language used for structuring and presenting hypertext documents on the World Wide Web. It was the fifth and final major HTML version that is now a retired World Wide Web Consortium (W3C) recommend ...

& CSS3 features and had the .azw3 extension; and version 10 introduced a new typesetting and layout engine featuring hyphens,

kerning In typography, kerning is the process of adjusting the spacing between Character (symbol), characters in a Typeface#Proportion, proportional font, usually to achieve a visually pleasing result. Kerning adjusts the space between individual le ...

and ligatures and has 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. Similar to

EPUB EPUB is an e-book file format that uses the ".epub" file extension. The term is short for ''electronic publication'' and is sometimes stylized as ''ePUB''. EPUB is supported by many e-readers, and compatible software is available for most smart ...

, 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 Free and open-source software (FOSS) is software available under a license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term encompassing free ...

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 lim ...

(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 syste ...

(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

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

hyphen The hyphen is a punctuation mark used to join words and to separate syllables of a single word. The use of hyphens is called hyphenation. The hyphen is sometimes confused with dashes (en dash , em dash and others), which are wider, or with t ...

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.

Footnotes

References

{{Ebooks Amazon (company) Computer file formats Electronic paper technology Ebooks