Why was my EPUB rejected?

The EPUB errors that get books rejected most often

Apple Books, IngramSpark, Kobo and other EPUB stores test files against the EPUB standard before they accept them, and EPUBCheck is the standard's official validator. These are the problems that most often stop a book, with the code EPUBCheck prints for each one.

A table-of-contents entry is blank (RSC-005)

One entry in the table of contents has no text, usually because a heading in the manuscript was empty or contained only a picture or a page break. Stores that run EPUBCheck, such as Apple Books and IngramSpark, reject this. Fix: Remove the empty heading in the manuscript (or give it a title) and rebuild the table of contents.

A linked file is missing from the book (RSC-007)

A chapter refers to an image, stylesheet or page that is not inside the EPUB. This is one of the commonest store rejections. Fix: Add the missing file, or remove or correct the reference to it.

A link points to a spot that does not exist (RSC-012)

A link, often in the table of contents, aims at a heading or anchor (the part after #) that is not on that page. This is the classic broken table-of-contents link. Fix: Fix the link target, or regenerate the table of contents after editing the headings.

A page is not valid XHTML and cannot be read (RSC-016)

One chapter file has broken markup, such as a tag that is opened and never closed. Readers stop at this point. Fix: Correct the markup on the line shown, or rebuild the EPUB from the original manuscript.

The book's language is not set (RSC-005)

Every EPUB must say what language it is written in, and this one does not. Fix: Add the language (for example en) in your book's metadata and export again.

The book loads something from the internet (RSC-006)

A chapter points to an image, font or file on a website instead of carrying it inside the EPUB. Stores reject this. Fix: Download the image or font, put it inside the book, and point to the local copy.

A file is used but not listed in the book's manifest (RSC-008)

The book's package file (the .opf) must list every file the book uses. One is missing from that list. Fix: Add the file to the manifest, or rebuild the EPUB so the list is generated for you.

The book uses a feature it does not declare (OPF-014)

A page uses something special, such as scripts, SVG drawings or content from the internet, without saying so in the package file. Fix: Declare the feature in the manifest, or (usually better) remove it from the page.

The mimetype file is missing or out of place (PKG-006)

Every EPUB must begin with a tiny file called "mimetype", stored first in the archive and uncompressed. This usually happens when an EPUB is unzipped and re-zipped with an ordinary zip tool. Fix: Re-export the EPUB from your writing software rather than re-zipping it by hand.

A link or file name is not a valid web address (RSC-020)

A file name or link contains a space or another character that is not allowed in a link. Fix: Rename the file without spaces or special characters and update the link.

The old-style table of contents has a different ID (NCX-001)

The book's older table of contents file (toc.ncx) carries a different identifier from the book itself. Fix: Make the dtb:uid in toc.ncx match the book's identifier, or rebuild the EPUB.

An image is in a format EPUB does not accept (MED-003)

An image uses a format outside the EPUB core set, such as TIFF or BMP. Fix: Convert the image to JPG, PNG, GIF, WebP or SVG.