Web Excursions 2022-05-20
Kindle, EPUB, and Amazon’s Love of Reinventing Wheels
in sending the files through the service they would be converted to Amazon’s KF8/AZW3 format, the result of which may not always be what you expected.
At the same time the Send to Kindle documentation noted that
support for AZW and MOBI files would be removed later on this year,
as the older formats weren’t compatible with all the features of the latest Kindle models.
EPUB
The history of the EPUB format can be tracked back to 1999,
with the version 1.0 release of the Open eBook Publication Structure (OEBPS).
Used by some of the very first dedicated electronic readers from the likes of Sony and Intel,
it essentially consisted of a manifested ZIP archive that contained pages written in a form of XHTML,
with CSS used for styling.
OEBPS went through several revisions over the years, and in 2007 it became the official technical standard of the International Digital Publishing Forum (IDPF).
At that point it was renamed to EPUB, short for Electronic Publication.
EPUB continued to evolve over the years,
and in 2016 the IDPF merged with World Wide Web Consortium (W3C)
in an attempt to bring the publishing industry inline with the latest in web development.
The current version of the EPUB format (3.2) was released in May of 2019,
and offers features such as the ability for Internet-connected devices to load fonts
and other content from outside the container file itself.
EPUB can still ultimately still be thought of as a relatively simple web page contained in a ZIP file.
As they are exceptionally easy to parse and render, you can find EPUB reader applications on even very low-end devices.
while the EPUB format does allow for Digital Rights Management (DRM), it is not part of the standard.
That means if a vendor wants to implement DRM in EPUB, they have to figure out how to do it themselves.
MOBI/AZW
Even older than EPUB, MOBI has its origins in the PalmDOC format from 1996.
Originally conceived as a way of storing large text files on the Palm Pilot,
the format offered little in the way of formatting outside the ability to mark the start and end points of paragraphs.
It did however offer basic bookmarking capability, which in some cases was used to offer a rudimentary table of contents.
Being that PalmDOC was a variation of the standard “Palm Database” file,
it also featured the ability to store various bits of metadata in a standardized header,
such as the author name, book title, and current reading position.
In 2000 MobiPocket, developers of ebook reader applications on Palm, Symbian, and later BlackBerry devices,
decided to take matters into their own hands and expand PalmDOC.
They added an HTML-like markdown language, improved support for images, and as it was an open format, even borrowed a bit from OEBPS.
in 2005, Amazon purchased MobiPocket, and in turn the rights to MOBI.
But rather than use the format as-is for the Kindle,
they added a new DRM scheme and cranked the format’s LZ77 compression to the maximum.
the first-gen Kindle only offered a relatively meager 250 MB of onboard storage and was limited to downloading new titles over a 3G cellular connection
From here on out Amazon essentially starts using AZW as a blanket term for their ebook containers,
and the actual formats underneath start getting a bit blurry.
AZW1
Known officially as Topaz, this proprietary Amazon format has little relation to MOBI/AZW beyond a shared DRM scheme and similar metadata header.
In addition to supporting larger images compared to the earlier formats,
it was unique in that each title could include its own fonts and glyphs
rather than relying on what was built into the Kindle itself.
AZW2
This actually isn’t an ebook format at all, so don’t be surprised if you’ve never ran across one.
Rather, this is a container file for executable Kindle applications and games.
KF8/AZW3
With the release of the first Kindle Fire tablet in 2011, Amazon needed a new format that could handle multimedia content.
The answer was KF8, which is essentially a combination of EPUB and MOBI.
it specifically picks up some of the EPUB 3.x features such as support for HTML5 and CSS3.
Amazon decided to move all of their readers over to AZW3 and make it the new standard for the marketplace.
all of them beyond the first and second generation are able to read them
thanks to redundant MOBI header information which is kept specifically for backwards compatibility.
KFX/AZW8
With the release of the Kindle Paperwhite 3 in 2015, Amazon rolled out their latest format, KFX.
Technical information about KFX is a bit hard to come by,
as it appears Amazon developed it in-house to be their “ultimate” book format.
improvements include
an enhanced typesetting engine,
additional fonts, and
support for JPEG XR images.
It also rolls in support for video and interactivity,
theoretically allowing the same format to be used for both books and software applications.
the most obvious change was the enhanced DRM
At this point the format and DRM is understood well enough
that it can be handled by third-party software,
but it takes additional steps and intermediary tools that aren’t required for AZW3 content.
It’s generally recommended that anyone who wishes to maintain their own local library of ebook files
should avoid this format altogether — though as more and more of Amazon’s library switches over,
that may mean you need to purchase your books elsewhere.
To their credit, Amazon has largely perfected the experience of buying and consuming electronic books