KDP EPUB Upload Error? How to Find and Fix It

You've finished your book, made your EPUB file, and uploaded it to Kindle Direct Publishing (KDP). Then you get an error, or the upload just won't finish. It's frustrating, especially when the file opens fine on your own computer.

The good news: most EPUB errors come from a short list of common problems. This guide helps you find which one you have and fix it. The quickest way to see what's wrong is to run your file through Ebook Medic, which checks EPUB files and fixes common problems.

What is an EPUB, quickly?

An EPUB is like a small zipped folder. Inside are your chapters, your pictures, your cover, and a few "map" files that tell reading apps how it all fits together. If one of those map files is missing or has a mistake, upload systems can refuse the whole book.

Step 1: Read the error message

Write down the exact words KDP shows.
Note when it happened: during upload, during conversion, or in the previewer.
Check KDP's help pages for that message. They change from time to time, so the latest advice will be there.

Step 2: Check your file for errors

Your EPUB might have several small problems, and KDP may only show one.

The easy way: Ebook Medic

Go to tools.ltd/ebook-medic.
Choose your EPUB file.
Read the results. It checks your book with the same rules as EPUBCheck, fixes what it safely can, and checks it again. Your book never leaves your device.
Get the fixed file and upload it to KDP. Some problems need a person to fix, and Ebook Medic tells you which ones are left.

The free technical way: EPUBCheck

EPUBCheck is the official free checker for EPUB files. Ebook Medic checks with the same rules. It's very thorough, but it can be harder to use, and the messages are written for technical people. If you're comfortable with that, it's a good second opinion.

Step 3: Fix the common problems

Here are problems that often cause upload trouble, and what to do.

The file isn't really an EPUB. Some programs save a file ending in ".epub" that isn't built correctly. Export again from your writing program and choose EPUB.
Broken links between chapters. A chapter or picture was renamed or deleted, but the book still points to it. Check that every chapter is still there.
Missing or broken table of contents. Rebuild the table of contents in your writing program, then export again.
Cover problems. The cover image is missing, very large, or saved in an unusual format. Use a standard JPG cover.
Odd characters in file names. Spaces, accents or symbols in picture or chapter names can cause trouble. Use simple names like "chapter1" and "cover."
Huge pictures. Very large photos can make the file too big. Shrink them before adding them to the book.
Password or copy protection. Don't upload a locked file. Upload the plain EPUB, and let the store handle protection.

Step 4: Preview before you publish

After uploading, open KDP's online previewer.
Flip through every chapter.
Check the cover, table of contents, and pictures.
For a closer look, Amazon offers a free program called Kindle Previewer that shows how your book looks on different devices.

Selling a print-ready PDF too?

If you also offer a PDF version (for example, a workbook or bonus guide), make sure it's not too large for download pages or email. PageKit can shrink or split PDFs right in your browser.

Apple Books said no, too?

Kindle and Apple Books both run EPUBCheck. Each store also has its own extra rules. So a clean EPUBCheck report helps a lot, but it can't promise a store will say yes.

The problems both stores reject most often are:

The "mimetype" file is missing, or it isn't the first file in the EPUB.
The book has no title, ID, or language set.
A file is missing, or a file isn't on the book's file list.
A file name has a space in it.

Fix these first. Then upload again and read any new message the store gives you.

Frequently asked questions

Why does KDP reject my EPUB when it opens fine on my computer?

Many reading apps are forgiving and will open a file with small mistakes. Upload systems are stricter and check the file's rules.

Can I upload a Word file to KDP instead?

KDP accepts some other formats, including Word files. Check KDP's help pages for the current list. Many authors still prefer EPUB for more control.

Is Ebook Medic connected to Amazon?

No. Ebook Medic is an independent tool that checks your EPUB file for problems and fixes common ones.

Will fixing the file change my words?

Fixes should only touch the file's structure, not your writing. Always preview the fixed book before you publish.