There are dozens of ways to make an ebook, but one format is emerging as the international standard: the EPUB. One day soon, the EPUB format may be the first ebook picture that comes to mind.

EPUB Defined

The International Digital Publishing Forum (IDPF) is dedicated to developing and maintaining the EPUB format. IDPF executive director Bill McCoy, who was at the forefront of EPUB’s creation, defines EPUB as “a portable document technology that’s converged with and built on the latest open web standards.” More specifically, EPUB is “a means of representing, packaging and encoding structured and semantically enhanced Web content … for distribution in a single-file format,” according to the IDPF.

EPUB 2, which was a successor to the Open eBook Publication Structure, became the IDPF standard in 2007. EPUB 3, the first major upgrade to the format, was ratified in October 2011 by about 300 member organizations, says McCoy, who was secretary of the IDPF’s EPUB 3 Working Group.

Free to Be EPUB 3

The “vision of EPUB 3 was really to converge this EPUB portable document standard with the latest and greatest web standards” such as HTML5 and to take advantage of the fact that the ebook market was shifting from dedicated e-readers (e-ink technology, black-and-white displays, and limited web connectivity) to tablets and smartphones, McCoy says.

The major updates to the EPUB format in EPUB 3 are as follows:

• Rich media support (audio and video)
• Interactivity support (e.g., quizzes and crossword puzzles)
• Global language support (e.g., vertical writing and right-to-left reading)
• Mandatory embedded font support (the inclusion of font files in the document)
• Enhanced metadata and navigation support (e.g., tables of contents are now HTML5-based)
• Annotation and bookmarking support
• Mathematic equation formatting capabilities
• Additional styling and layout capabilities for reflowable content (meaning the content adapts its presentation to the device on which it is being viewed)
• Fixed-layout support (for prepaginated and reflowable content)
• Accessibility features (e.g., enhanced semantic tagging and text-to-speech)

Strengths and Weaknesses

Joshua Tallent, chief ebook architect at the ebook design company eBook Architects, says EPUB’s biggest strength is its industry support across different devices, publishers, and retailers that “see it as a standard that they can apply without having to build their own.”

EPUB is also dynamic: Publishers “can do things like change the font size and have the document reflow, so all the text is still visible,” whereas with a “PDF on a small screen you have to kind of pan and zoom around, which is not a very convenient way to read,” says McCoy.

On the flip side, Ori Idan, CEO of Israeli technology company Helicon Books, sees EPUB’s complicated structure as a hindrance for the standard. “[Y]ou don’t have automatic software that can generate EPUB. … Especially if you add some more features like sound, video, all the features of EPUB 3, then you can’t make it with the click of a button.”

Another problem with EPUB occurs because of the variety of devices on the market. “People have this idea that EPUB is a standard and it’s going to work great across everything, but … [i]t looks different across different devices,” says Devorah Ashlem, senior project manager at Data Conversion Laboratory (DCL), a conversion services company.

Tallent and McCoy both cite the example of Amazon and Apple converting EPUB files to their own proprietary, locked-down formats as a problem for consumers. For example, “[I]f you buy an EPUB file from the [Apple] iBookstore, you can use it on your iBooks application, but you can’t open it in a NOOK device or in a Kobo application; even a Kobo application on that same iPad can’t open a file you bought from the iBookstore,” says McCoy.

For Tallent, there’s a common misconception that “it’s not about what kind of device you have, it’s about the reading system that’s on that device.” He defines the reading system as the application that opens a file and displays it on an e-reader screen. For example, the Kindle Paperwhite uses a reading system different from a Kindle Fire and the Kindle app on an Apple device, even though they are all Amazon products. “And while there’s a lot of core code that’s going to be used between the three different reading systems … they are still different applications. …”

Slow and Steady Wins the Race

“The adoption rate [of EPUB 3] is much slower than I thought,” says Idan. “I think that this is a very conservative market, and it takes a long time to penetrate through this market. If you think in terms of technology, 2 years [since EPUB 3’s ratification is] a lot of time. If you think in terms of publishing, 2 years [is] not a long time.”

Apple was one of the first companies to use EPUB 3 commercially because its software is naturally compatible with EPUB 3’s features, such as the ability to sync text with prerecorded audio. “They could have invented a proprietary way to do that, but because EPUB 3 had that already defined, it was much simpler and easier for Apple” to support EPUB, says McCoy. “I think in this case they saw that adopting a consistent standard made it easier for them to get content from the different publishers and authors and it made less work for them to develop [their] platform.”