The PDF file is that kid in school who talks to everyone. Not just all the other kids in different groups, but this kid chats up the custodians, receptionists, and even the crusty retired librarian. PDF files are the oldest of the lot, and as far as documents go, they’re an industry standard. This means that most electronic devices are compatible with PDF formats. And for an added bonus, not only is it incredibly easy to turn a Microsoft Word document into a PDF (hint: you’ll usually end up having to convert to PDF for the other formats regardless) but this format is also easiest for printing on standard-size paper.

A winner, right? But hang on a moment—there’s a catch.

The first big drawback of PDF files is that they tend to be large. When you start accumulating PDF files on smaller devices with limited memory, you run into problems storing your reading library.

PDFs are also not optimized purely for e-readers or reading books from a mobile device. They use something called a “fixed layout,” which means the text in these documents does not adjust to accommodate a screen’s size. The text is static, so that no matter how you look at it, it will always look exactly the same way, regardless of device. On a computer, this is no problem. Try reading that 350-page document on your Android phone, however, and you will notice that not only is the text far too small to read but zooming in requires you to move the text around with your finger in order to follow it. Not exactly a seamless, user-friendly experience.

FILE TYPE:  ePUB (Electronic Publication)

Compatible platforms: Computers, e-readers, e-reader applications, smart devices

Ideal platform for this file: E-readers, smart devices, tablets

When it comes to e-readers and e-reader applications, ePUB files are the standard format. Flexible and widely adopted, ePubs were designed with reading in mind. The text flows so that readers can select a text size, and the file will automatically adjust to fit on the screen, requiring users to do little more than swipe to flip the page.

The ePUB format’s greatest strength is its ability to accommodate multimedia and even interactive features. It’s easiest to think of it like a web page, designed to support HTML (including HTML5), CSS, and more. Image-heavy pages render beautifully, which means even children’s picture books can be enjoyed. The ePUB format even has the ability to accommodate comics and graphic novels.

Because ePUB files are optimized for books, they are currently the publishing industry’s preferred file type for any e-reading platform and the most widely used by booksellers.

However, unlike PDFs, most word-processing programs do not have a useful “save as ePUB” option. The complexity of the format means that authors will need to use e-book-specific software (such as Calibre, Scrivener, or Sigil) in order to create these documents, or find a service or contractor to convert the file for you.

FILE TYPE:  MOBI (Mobipocket)

Compatible platforms: Amazon Kindle devices and applications only

Ideal platform for this file: Amazon Kindle devices and applications

We’re in the age of proprietary software, and e-book formats are no exception. Bought by Amazon for their Kindle devices, MOBI was created exclusively for the Kindle, and these files are likely to be supported for some time. With an image size limitation (64K), this format is best used on smaller devices.

The good news is that the MOBI format has fewer hardware requirements and a lower file format. The bad news? This is because MOBI is not the mighty and all-powerful ePUB. It is a far older format, designed to be used on devices with limited capabilities. MOBI files also use outdated GIF image formats, which means reduced resolution, fewer colors, and limited compression—so this is not the best choice for enhancing books that contain images or illustrations.

Although Kindle only uses MOBI files, you can convert many other formats (DOC, DOCX, EPUB, HTML, TXT, RTF, or PDF) to MOBI for Kindle. Visit https://kdp.amazon.com/en_US/help/topic/G200634390 for more information on supported formats and how to convert them.

These days, most booksellers will accommodate different formats according to your needs. By familiarizing yourself with these file types and knowing the pros and cons of each, you won’t accidentally lock yourself into a more restrictive format and negatively affect your sales or readers’ experiences.

Before you decide on any file type, just remember to do your research for each bookseller, and ensure you meet their technical requirements.

Digital publishing is a beautiful world—with many options and many online resources to steer you in the right direction. And eventually, you’ll discover that the more you know, the more easily you will be able to navigate the world of self-publishing…one technical term at a time.