The upload went through. The preview looked fine. Then, three days later, an email arrives: your Kindle book has a quality issue and needs corrections. Or Apple Books bounces your EPUB with a validation error that reads like a compiler message.
Most ebook rejections come from a short, predictable list of formatting mistakes. They usually start in the source document, a Word file or a print layout that was never built for a screen, and they show up when a retailer converts, validates or reviews the file.
This post covers 12 common ebook formatting mistakes, what each one triggers at the retailer, how to fix it at the source and how to check for it. It finishes with an ebook validation workflow, including EPUBCheck and a small Node script that scans an EPUB for the most common problems before you upload.
How Ebooks Get Rejected (Not Always at Upload)
Upload or Conversion Failure
The first gate is the file itself. On KDP, reflowable ebooks must be EPUB, DOCX or KPF. According to KDP's MOBI FAQ, Amazon stopped accepting MOBI files for reflowable books on August 1, 2021, and for fixed-layout books on March 18, 2025. Old tutorials that tell you to upload a MOBI will lead straight to an error.
Quality Review After Publishing
The second gate catches many authors by surprise. A book can be live and still be flagged later. KDP's Guide to Kindle Content Quality sorts problems by severity. It says "any Critical Issue will result in the book being removed from sale until corrections are made." Moderate distracting issues can leave the book on sale but add a temporary quality warning to its product page, which hurts sales almost as much.
KDP also notes that "Typos are among the most common quality issues customers report," and many of the examples it lists are really formatting mistakes.
Validation at Other Retailers
Apple Books, Kobo and most distributors check EPUB files against a standard. EPUBCheck, the official EPUB validator, is maintained by the W3C and describes itself as "the official conformance checker for EPUB publications." Its own documentation puts the stakes plainly: "Most retailers will not accept an EPUB file unless it successfully passes EPUBCheck scrutiny."
Reflowable vs Fixed Layout: The Root of Many Mistakes
A print book has fixed pages. A reflowable ebook doesn't. Readers change the font, the text size, the margins and the background color, and the text reflows to fit a phone, a tablet or an e-reader. There are no page numbers, no fixed line breaks and no guarantee that two things will appear on the same screen.
Most ebook formatting mistakes come from treating an ebook like a print PDF. Indents made with spaces, page numbers in the text, black text forced onto the page and pictures of tables all assume a fixed page that doesn't exist.
Fixed-layout ebooks are the exception, used for picture books, cookbooks and heavily designed books where position matters. They follow their own rules and are best handled by someone experienced with them. Everything below is about reflowable ebooks, which cover most novels and nonfiction. If you're starting from scratch, this guide on how to format a book for self-publishing covers the basics of setting up a clean manuscript.
The 12 Ebook Formatting Mistakes
Layout and Spacing
1. Inline page numbers, headers and footers. These creep in when a print PDF or a print-formatted Word file is converted. On screen, a stray "27" appears in the middle of a paragraph. KDP's quality guide says inline page numbers "must be removed." Fix: start from a manuscript without print headers and footers, or remove them before converting. Check: search the text for lines containing only a number.
2. Tabs and spaces for indents, blank lines for spacing. Pressing Tab or the space bar to indent, or Enter twice between paragraphs, produces uneven spacing after conversion. The indents vary by device and blank lines pile up at screen breaks. Fix: use a paragraph style with a first-line indent and spacing set in the style. Check: turn on hidden formatting marks in Word, or run the script below.
3. Manual page breaks made with Enter. Hitting Enter 20 times to start a new chapter creates blank screens on some devices and odd gaps on others. Fix: use a real page break or a chapter heading style that starts on a new page. Check: preview at several text sizes.
Text and Fonts
4. Forced font colors, sizes and alignment. Text set to black looks fine on white, until a reader switches to dark mode and the words disappear. KDP specifically flags "Forced white text or forced black background that causes text to be unreadable," along with forced alignment and forced body text size. Fix: leave body text on "Automatic" color and default size, and let the reading system handle it. Check: preview in dark mode.
5. Unsupported and junk characters. Symbol fonts, unusual Unicode characters and leftover soft hyphens show up as boxes, question marks or broken words. KDP lists jumbled text and soft hyphens among its quality issues. Fix: use standard characters and UTF-8 encoding, and replace decorative symbols with images or plain text. Check: page through the book in Kindle Previewer.
6. Embedded fonts used carelessly. Embedding fonts can trigger validation warnings, increase file size and break reader font choices. Font licenses also vary, and some don't allow ebook embedding. Fix: keep body text in the default font, and embed only licensed fonts for headings if you need them.
Structure and Navigation
7. No real heading styles. Chapters typed in bold, large text look like headings but aren't. Without proper heading styles, conversion tools can't build the navigation readers use to jump between chapters. Fix: apply Heading 1 to every chapter title and use heading styles consistently.
8. A missing or broken table of contents. Readers expect a working table of contents, and KDP lists "A link in the Table of Contents (TOC) that does not work" as a quality issue. EPUBCheck also reports links pointing to files or anchors that don't exist. Fix: generate the TOC from heading styles rather than typing it, then click every entry in the preview.
9. Broken or problem external links. Links to dead pages, or links to prohibited sites, can be flagged. Fix: test every URL before upload, keep links to a minimum and avoid linking readers to competing stores.
Images and Tables
10. Blurry images and images with small text. Low-resolution images look worse on high-resolution screens, and text inside an image can't be resized. KDP flags "blurry images and images with illegible text." Fix: use sharp images at a suitable resolution, and never put body text, charts with tiny labels or tables inside an image.
11. Wide tables. A table that fits a printed page can be cut off on a phone at the default font size, which KDP lists as a quality issue. It also flags tables used for layout rather than data. Fix: simplify wide tables, split them or turn them into lists. Check: preview on the smallest phone size.
Content and Metadata
12. Metadata that doesn't match the file, and duplicated or missing content. A subtitle in the listing that doesn't appear in the book, a chapter pasted twice, missing images or an old draft uploaded by mistake all count as quality issues. KDP removes books with the wrong content from sale. Fix: check the title page against your listing, and open the exact file you uploaded, not the one on your desktop.
Validate Before You Upload
Run EPUBCheck
EPUBCheck runs on Java and works from the command line:
java -jar epubcheck.jar mybook.epub
The output lists each problem as an ERROR or a WARNING, with the file and line inside the EPUB. Errors usually mean rejection at retailers that validate. Warnings are worth reviewing but often aren't fatal. Fix problems in your source document and export again where you can, rather than patching the EPUB by hand, so the fix survives the next revision.
Preview in Kindle Previewer
Amazon's free Kindle Previewer shows how the book will look on Kindle e-readers, phones and tablets, in different orientations and fonts. Click every TOC entry, flip through every chapter and turn on dark mode. Previewer shows you how the book looks rather than grading it, so you still have to do the looking.
A Tiny Lint Script
EPUBCheck confirms the file is valid. It won't tell you that you indented with spaces or forced black text, because those are valid HTML. This small Node script catches those mistakes. It needs no dependencies and reads an unzipped EPUB folder:
// lint-epub.js: flag common ebook formatting mistakes in an unzipped EPUB
// Usage: unzip mybook.epub -d mybook && node lint-epub.js mybook
const fs = require('fs');
const path = require('path');
const checks = [
{ name: 'Empty paragraph (blank line used for spacing)', re: /<p[^>]*>\s*( | | )?\s*<\/p>/gi },
{ name: 'Run of non-breaking spaces (manual indent)', re: /( | | ){2,}/gi },
{ name: 'Tab character', re: /\t/g },
{ name: 'Forced text color (inline style)', re: /style="[^"]*(?<![-\w])color\s*:/gi },
{ name: 'Forced font size (inline style)', re: /style="[^"]*font-size\s*:/gi },
{ name: 'Possible inline page number', re: /<p[^>]*>\s*(page\s*)?\d{1,4}\s*<\/p>/gi },
{ name: 'Soft hyphen', re: /|­/g },
];
function* walk(dir) {
for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
const full = path.join(dir, entry.name);
if (entry.isDirectory()) yield* walk(full);
else if (/\.x?html?$/i.test(entry.name)) yield full;
}
}
const root = process.argv[2];
if (!root) {
console.error('Usage: node lint-epub.js <unzipped-epub-folder>');
process.exit(1);
}
let total = 0;
for (const file of walk(root)) {
const lines = fs.readFileSync(file, 'utf8').split('\n');
lines.forEach((line, i) => {
for (const { name, re } of checks) {
re.lastIndex = 0;
if (re.test(line)) {
console.log(`${path.relative(root, file)}:${i + 1} ${name}`);
total++;
}
}
});
}
console.log(total ? `\n${total} possible issue(s) found` : 'No common issues found');
process.exitCode = total ? 1 : 0;
Run against a test chapter seeded with mistakes, it reports:
OEBPS/ch1.xhtml:4 Run of non-breaking spaces (manual indent)
OEBPS/ch1.xhtml:5 Empty paragraph (blank line used for spacing)
OEBPS/ch1.xhtml:6 Forced text color (inline style)
OEBPS/ch1.xhtml:7 Forced font size (inline style)
OEBPS/ch1.xhtml:8 Tab character
OEBPS/ch1.xhtml:9 Possible inline page number
OEBPS/ch1.xhtml:12 Soft hyphen
7 possible issue(s) found
On a clean file it prints "No common issues found" and exits with code 0, so you can drop it into a build script or CI step. It deliberately ignores background-color and a number inside a normal sentence, so it doesn't drown you in false alarms. Treat every hit as a lead, not a verdict, and fix it in the source document.
A Pre-Upload Checklist
- No page numbers, headers or footers in the text
- Indents and spacing come from paragraph styles, not tabs, spaces or blank lines
- Chapters start with real page breaks and Heading 1 styles
- Body text has no forced color, size or alignment, and reads correctly in dark mode
- No boxes, question marks or broken words from unsupported characters or soft hyphens
- The TOC is generated from headings, and every entry works
- Every external link opens the right page
- Images are sharp, and no body text lives inside an image
- Tables fit a phone screen or have been simplified
- The file matches your title, subtitle and description, with no duplicated or missing content
- EPUBCheck reports no errors, and the book has been previewed on several devices
When to Hire a Formatter
DIY formatting works well for straightforward novels and simple nonfiction. It gets harder with complex nonfiction, many images, tables, footnotes, poetry with exact line breaks, fixed layout or a book going to several retailers. It's also worth getting help if a file keeps coming back with quality flags.
Western Reflections Publishing offers professional book formatting services for print interiors, and separate EPUB and Kindle conversion for ebooks, with files checked in Kindle Previewer before delivery.
FAQs
Why was my ebook rejected by KDP?
Usually because of an unsupported file type, a conversion failure or a quality issue found after upload. Common quality flags include inline page numbers, forced font colors, broken table of contents links, blurry images, tables cut off on screen and metadata that doesn't match the book. KDP's email names the issue category.
What are common ebook formatting mistakes?
The most common are page numbers left from print files, tabs and spaces used for indents, blank lines for spacing, missing heading styles, broken tables of contents, forced font colors, unsupported characters, blurry images and wide tables. Most come from treating a reflowable ebook like a fixed print page.
How do I validate an EPUB file?
Run it through EPUBCheck, the official validator maintained by the W3C, using java -jar epubcheck.jar mybook.epub. Fix every error and review the warnings. Then preview the book in Kindle Previewer or on real devices, because a valid file can still have visual and readability problems.
Can an ebook pass upload and still get a quality warning?
Yes. KDP reviews quality after publishing, often in response to customer reports. Depending on severity, a book can be removed from sale until it's fixed, or stay on sale with a temporary quality warning on its product page. Critical issues always lead to removal until corrected.
Should I convert a PDF to an ebook?
Generally no. PDFs are fixed print layouts, so converting them carries over page numbers, headers, hard line breaks and spacing problems. Start from a clean Word file or source document with proper styles, or rebuild the ebook in a formatting tool designed for reflowable text.
What file format is best for uploading an ebook?
For KDP, use EPUB, DOCX or KPF. MOBI is no longer accepted. For Apple Books, Kobo and most distributors, a valid EPUB is the standard. A single, well-built EPUB that passes EPUBCheck usually works everywhere, which is why many authors make it their master ebook file.
Wrapping Up
Ebook formatting mistakes get books rejected because ebooks aren't printed pages. Format for reflow, use styles instead of spaces, let readers control color and size, build the TOC from headings, keep images sharp and tables small, and match the file to your listing. Then run EPUBCheck, lint the file and preview it before you upload, not after the quality email arrives.
If you'd rather hand the file to someone who does this every day, Western Reflections offers professional book formatting services built for KDP, IngramSpark and other retailers.
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