As the popularity and consumption rates of e-books continue to skyrocket, the technology behind them is constantly evolving. From DRM solutions to desktop publishing tools, it seems like the markets are being hit with a new advance every day like an endless storm. In this constantly changing environment, publishers and authors are faced with many different choices in how they deliver their content to readers, and how the content is viewed.
Perhaps the question I'm asked most often regarding these choices is the differences between e-book formats; particularly why and how to use which one. I thought a blog post to clarify this topic could be beneficial to readers, so here we go. :)
Although there are many e-book formats on the market now, I want to focus on two most popular and open formats currently used; EPUB and PDF. Some might argue that PDF isn't really open due to the fact that it was created by Adobe. Even so, let's not forget that the PDF spec is now completely open and has become an ISO standard
. Therefore, I consider it to be open for the purposes of e-book content delivery and publishing. Let's take a look at some differences between the formats to better understand their strengths and weaknesses;
PDF documents are what we call fixed layout documents, where the layout and positioning of elements contained within are fixed independent of the viewing medium. A PDF document will look pretty much the same on whatever device we view it on, whether it's a desktop computer, tablet device or mobile phone. The design of the document remains exactly the same as we created it in our PDF creation tool. In contrast, EPUB documents support reflowing; which in essence means that EPUB documents dynamically adapt to the viewing medium to maximize compatibility across platforms. The logic behind EPUB files are based on the same foundation as web pages. You can think of the dynamic behavior similar to what happens when you resize your browser window. For example, go ahead and try resizing the window looking at this blog post, you'll see what I mean.So the main difference between these two formats is fixed versus dynamic layout.
Of course, the differences don't end there. When reading EPUB files, you can change your font family and font size on the fly, again because it is based on web technology and layout changes occur dynamicly. PDF files have begun allowing similar features lately, but they're not really usable in my opinion, because fixed design is the main idea here and when you increase the size of a font your design is bound to get messed up quite a bit.
Both formats allow rich media to be included as of now. The EPUB3 specification supports HTML5 Video/Audio content, PDFs have had this support for a long time. However, most reader devices are not capable of rendering video so this feature may not be very viable yet, unless you're specifically targeting devices with multimedia capabilities like the Apple iPad or Samsung Galaxy Tab tablet devices. Also, both formats support Adobe DRM, the leading mechanism for e-book digital rights management. Therefore, you can protect your content and control the access rights to it using both formats if you choose to do so.
Now that we've covered a bit of ground about the differences and features of the two leading e-book formats, let's discuss how we can make a choice. From my experience, making the choice becomes a lot easier once we consider these points;
- Design: Is it important for us that our content is displayed exactly as we designed it?
- Target Mediums: Are we targeting tablet devices only? Or do we wish to target e-ink readers and desktop readers as well?
- Rich Media: Is our publication mostly based on rich media such as images and even audio/video content? Or is it mostly text, like a novel?
These points will not only help you choose the right format for your use case, they may also assist you in identifying your audience.
Please feel free to discuss through comments, and thanks for reading!