Book Formats

“Which file formats do I need to load my book to vendors and distributors?”

In the beginning, you needed a MOBI for Kindle Direct Publishing (KDP), and an EPUB for all the other vendors and distributors.  Very few sites accepted Word documents.

Formats have evolved since the early days of self-publishing. Let’s look at what works now.


Word docs

Many vendors will now accept a correctly formatted Word docx (filename.docx) which are converted to EPUBs. Many of them have instructions for you to follow.

Smashwords accepts only Word doc files (filename.doc) even though Microsoft hasn’t supported this file format for years. The Word file is converted via a proprietary process to an EPUB. Unfortunately, Word files don’t always convert easily. More on this later.


In the beginning, Kindle Direct Publishing accepted only mobipocket (mobi) files which were converted to a proprietary format for Kindle devices.

After June 28, 2021, KDP will no longer accept mobi files for new and updated reflowable ebooks. A nasty wrinkle is that many book reviewers prefer mobi for use on their older Kindles. You can upload an epub file to the Kindle Previewer and then export a mobi file from there.


EPUB is the gold standard for ebook files.  They’re now at version 3, though all versions are accepted at all vendors. Not all ereaders (there millions of old devices still in use) are advanced enough for the full functionality of version 3.

Use Adobe Digital Editions to view an epub on your device. For instructions, see  How to Preview Your Epub File Before Uploading to Retailers

All vendors and distributors, including KDP and Smashwords, now take EPUBs.

Before you upload, all EPUBs must validated by EpubCheck, a Java-based validation tool.

Word doesn’t create any form of ebook file.  You can use Adobe InDesign or one of the many apps out there; Sigil, Calibre, Jutoh to name a few, that use a Word document as their basis.

Whichever app you use, check for the validation. Don’t worry, Woven Red provides validated files.


These are PDF files, created in Word or Adobe InDesign, that have a flowable structure. Vendors will take them but the conversion is unreliable. Some reviewers prefer them.

Print Books

Regardless of whether you use KDP, IngramSpark, or a local printer, all files for print books are PDFs. They are essentially a digital picture of your words that is loaded to a huge digital printer that will create your book.

Word and Adobe InDesign both create PDFs. Go to their support sites for details.

The same PDF for the same trim size can be loaded to KDP, IngramSpark, and most other printers. Local printers may vary, so do check with them.

Use Adobe Acrobat in two-page view to preview your PDF file before loading. For instructions, see How to Preview Your Print Book.


We’ve been talking about files for the interior of the book, its content, front and back matters.

Ebook covers are jpeg files of the front cover. The standard size is 1600 pixels by 2560 pixels, or a width to height ratio of 1:1.6. The jpegs are embedded in the book files to present as the first page when you open the file on an ereader.

Print book covers are PDFs sized to wrap the interior pages, calculated according to the trim size and the spine size.

The most common issue with print covers is a variation in spine size which depends on the page count and the thickness of the paper. KDP and IngramSpark provide downloadable templates that factor in trim size, bleed margins, page count, and paper thickness. Local printers will have their own paper stocks, so do check with them. With thinner books, you might be able to get away with the same cover file for all printers.

The standard cover is paperback. Hardback and dust-jacketed covers are also available on IngramSpark. KDP doesn’t have this option, but IngramSpark will distribute the books to KDP for you. When this happens you can claim your book via KDPs Author Central.


If you’re not going with Word files, you will need the following for a successful upload to vendors and distributors.

Ebook interior EPUB to upload, MOBI for reviewers
Ebook cover JPG
Print book interior PDF
Print book cover PDF for each printer, as needed

Formatting in Word

Getting your Word document formatted correctly for loading to vendors and apps can be a tedious, frustrating business. Print book precision is demanding and can cause hair loss. You can follow the instructions on the various vendor sites or you can sign up for Mastering Word for Fiction Writers, the definitive online course to save time, money, and effort and tame the beast that is Word. Don’t fight your book, write your book!

Five Giveaways to Amateur Self-Publishing
Why Do a Print Book?
Why Your eBook Doesn’t Look Like Your Print Book