Ebook Formatting Answers: Ebook Standards

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Each week, we’ll answer your burning questions about ebook formatting. This week’s question is about universal and proprietary standards for ebooks.

Q. Different ebookstores can reject your ebook if it doesn’t meet certain standards for ebook files. What are some of these standards for ebook formatting and who sets them?

A. All the different platforms have different criteria, and they all trigger problems different ways. They may publish these standards openly, but there’s a bit of alchemy and randomness involved too.

Q. So how do I know if my book will be accepted?

A. You just sort of have to see what happens when you submit your book. Normally the baseline is that the book should be a valid EPUB. And if that’s the case you are likely to have a book that gets accepted. With some caveats. (Books produced with Pressbooks book formatting software are designed to meet all the ebookstore standards, so it’s rare that a Pressbooks user would encounter an issue.)

Q. So how can I check if my ebook is going to pass before I submit it?

A. There’s a great (paid) tool called FlightDeck. This is the best tool out there–it takes your book and checks everything and tells you in detail which platform is going to be annoyed by what thing. (In some cases, there are certain things that a platform won’t like, but it will accept them anyway, so don’t panic if you see some issues.) On the rare occasions when we have a mysterious problem with a book, we usually go to FlightDeck to find out what’s going ion. FlightDeck will tell you based on all the platforms what the problems are. And whether something is just a warning that a certain platform doesn’t a certain thing or a specific problem that really needs fixing before you submit your book.

Q. Why do the stores care about the quality of my ebook formatting? Are they just protecting their readers from a bad user experience?

A. Because they are reading systems, it’s reading software, and some of the reading software will choke on certain problems. Because everyone has their own software platform to display their ebooks that treats things slightly differently, certain platforms might break with an EPUB that has x or y in it. Or they’ve decided that that element for whatever reason is something they’ll reject. Take Kindle for instance: If you have a very small cover image they might reject your book. And that’s because they want nice high-res image as covers in their system.

Q. Since different bookstores have different proprietary requirements for ebook formatting, is there any governing body that regulates the universal standards for ebooks?

There is the International Digital Publishing Forum. They’re the keeper and maker of the EPUB specifications for valid EPUBs.

Q. How do I tell if my EPUB is valid?

At Pressbooks, we actually validate all the EPUBs as they go through our system, so if you sometimes see one of those messages that say there was an error with your book, it’s usually because something’s not valid in your EPUB. And that is almost always going to be something that you have in the content. So if you see that error you should go to and see if you can figure out what the problem is.

Q. Sometimes I’ve seen a message like this, and it says there are notifications for me. But I can’t find the notifications.

The notifications should be sent to the administrator’s email address. You can enable that under Settings / Export.

Do you have questions about ebook formatting? Email We may just answer your question in a future blog post.