Checking out the FlightDeck checker for epub files

Epub is meant to be a standard but it has so many variants as retailers and distributors brew up their own particular versions that it can be a nightmare to produce a file that passes muster.

Often, the only way of finding out whether your epub is going to pass inspection is to upload it to a distributor and then find out it fails on some arcane point which isn’t explained clearly.

It’s disheartening and time-consuming to go back repeatedly to work out a trial-and-error way of producing an epub file that passes the particular conditions for a particular distributor.

But now a new, easy-to-use epub checker promises to end self-publishers’ frustrations. The FlightDeck online tool will tell users whether an epub file will be accepted by the major ebook distributors and if it doesn’t pass a check, it will tell you why and how to make changes.

FlightDeck has been produced by eBook Architects, which is owned by Firebrand Technologies, a publishing industry technology services company. It covers Epub 2 and Epub 3 files and is available for use now as a two-month open beta. The firm claims the tool will uncover EpubCheck errors with deeper validation and best practices clearly explained.

It features a Retailer Acceptance Grid to tell users if their Epub files will be accepted by retailers, including Apple, Barnes & Noble, Google, Kobo, plus NetGalley.

The grid was developed with direct input from retailers and includes the same validation checks performed by their systems to show potential problems before files are uploaded for sale.

FlightDeck also allows users to edit their Epub metadata and offers a wide range of statistics and information about the content of Epub files.

Well, there’s nothing like using a service to find out how well it works, so I tried out a couple of files.


The interface is a slick, minimalist set-up. You can drag and drop a file or use the uploader. It’s quick to upload a file, process and validate it, I timed the whole procedure at under a minute, which is a whole lot less than it can be uploading a file to a retailer.

First, I uploaded a book which I recently designed and formatted, Charlotte’s Wedding by Mary Rizza. I didn’t anticipate any problems here as I produced the file with Jutoh and the book had a simple table of contents, which is often where epub problems arise. The book is on sale at Amazon and had passed its mobi check with no problems.

The book passed the FlightDeck validation test, with the message that there were no warnings or errors.


However, closer inspection of the Retailer Acceptance Grid revealed there were a few minor problems with some of the retailers, notably with missing ISBNs, which would obviously be inserted on uploading to a distributor. The discrepancies were clearly explained and linked to entries in the FlightDeck handbook which gives further help.

I was expecting problems with the second book I uploaded, Free WordPress by myself. For this book, I devised a bespoke table of contents which had sailed through mobi validation but hit a wall with epub sellers which don’t like anything out of the ordinary with tables of content. I’d had to redo the ToC to pass epub checks with this book, but for the sake of this test I uploaded the original file to see what it found.


True to expectations, I was very soon greeted with the message, “Error! This file is not a valid EPUB file. Yet.” The validation messages were clear and pointed to the areas that needed attention.

It was a short test but proved to me the worth of the FlightDeck checker. As well as providing a fast and reliable validation of a file, it also produces an exhaustive range of invaluable statistics covering external links, embedded fonts, total of characters, words, lists, tables and images, file sizes by type, largest files, an array showing image dimensions, languages, Start Reading location, header levels and table of contents.

It’s a brilliant tool and very quick and easy to use. It’s well worth using it just for the stats, even if you’re not interested in selling an epub version of your book.

During the open beta test, eBook Architects will collect feedback on the features and functionality of FlightDeck and make plans for future enhancements and additions. Users are encouraged to use the site often and send feedback and suggestions to the development team at any time.

Lead developer Derek Kurth says, “FlightDeck sets high expectations for the quality of epub files but also makes it much easier to meet those expectations. Consistent, high-quality files make ebook distribution easier and less frustrating and deliver the best possible reading experience for consumers.”

Firebrand Technologies was set up in 1987 to provide software and services to publishers. The firm owns eBook Architects, a leading ebook design and conversion services.