More people are reading ebooks than ever before.
To complicate matters further, not all e-readers support all formats.
EPUB
EPUB is the most widely adopted ebook file format.
Amazon Kindle devices cannot read it (except for the Kindle Fire tablet).
MOBI
Like EPUB, the MOBI format also grew out of the old OEB format.
Amazon bought the company in 2005 and allowed it to flourish for 11 years.
There are a few key differences between EPUB and MOBI.
Most pertinently, it is not open standard and, therefore, is not publicly available.
It also cannot support sound or video.
Once again, its supported by all the major e-readers with one exception: the Barnes and Noble Nook.
Note:The MOBI format also uses the PRC extension.
AZW and AZW3
The AZW and AZW3 extensions are Amazon’s two proprietary ebook formats.
AZW is the older of the two; it debuted alongside the first Kindle back in 2007.
AZW3 arrived in 2011 with the release of the Kindle Fire reader.
AZW3 is more advanced than AZW.
It supports more styles, fonts, and layouts.
Behind the scenes, both formats are extremely similar to the MOBI format.
Unlike MOBI, the Amazon formats both support video and sound.
Because AZW is proprietary, it is not as widely supported on e-readers as EPUB and MOBI.
IBA
Technically, the format is very similar to EPUB.
The iBook format supports video, sound, images, and interactive elements.
The last major ebook format in circulation is PDF.
Its big downside is the lack of native reflowing.
All the dedicated ebook formats offer reflowing based on the sequence of objects in the content-stream.
However, tagged PDFs are still not well supported by ebook readers.
They were proprietary formats that Sony created for use on its own range of ebook readers.
LRS is now open standard, but LRF and LRX remain closed.
Regardless, Sony has abandoned all three formats in favor of EPUB.
FB2
The XML-based FB2 started life in Russia.
It is common among ebook collectors thanks to its ability to store metadata within the ebook file itself.
DJVU
DJVU is popular in the scientific community.
Note:You canreduce the size of a PDF with a few compression tricks.
LIT
LIT was Microsoft’s proprietary ebook format.
When DRM-enabled, the books were only readable on the Microsoft Reader app.
In 2011, Microsoft discontinued the LIT format.
Reader vanished earlier this year.
RFT
The Rich Text Format is compatible with every e-reader on the market.
EPUB vs. MOBI vs. AZW: Which One Is Best?
In truth, the only formats you better worry about are EPUB, MOBI, and AZW.
If you want to create a library that’s predominately Kindle-specific, choose MOBI.
It doesn’t have quite as many features as AZW but more devices can read it.
If you’d like to learn more, check outour introduction to ebookstoo.
