TL;DR: EPUB formatting broken after conversion? Fix missing images, lost bold text, broken hyperlinks, and other common EPUB issues with this guide.
What Is This Guide About?
EPUB formatting broken after conversion? Fix missing images, lost bold text, broken hyperlinks, and other common EPUB issues with this guide.
It is designed to help readers move from uncertainty to a repeatable result without extra software, hidden steps, or unnecessary account creation.
Why It Matters
A clearer process matters because troubleshooting often becomes messy when tools hide the real trade-offs. Readers need a fast way to compare options, avoid broken formatting, and choose a method that respects privacy and time.
How It Works
The best results usually come from a simple sequence: prepare the source file, choose the right converter or workflow, check the output, and keep only the version that preserves structure. That approach is especially useful for troubleshooting because it keeps the process repeatable.
Practical Steps
Why EPUB Formatting Breaks During Conversion
EPUB formatting issues almost always come from the conversion step, not the EPUB format itself. EPUB is a well-designed format that supports rich formatting, images, hyperlinks, and structured content. The problem is that many converters do a poor job of extracting and mapping the source file’s formatting into proper EPUB structure.
The most common source of problems is PDF to EPUB conversion. PDFs use fixed positioning for every element, while EPUB is reflowable. Bridging this gap requires sophisticated analysis of fonts, spacing, images, and document structure — which many basic converters skip entirely.
The 8 Most Common EPUB Formatting Issues (and How to Fix Them)
Issue 1: Bold and Italic Text Disappeared
What happened: Your source file had bold headings, italic emphasis, and monospace code, but the EPUB shows everything in the same plain font.
Why it happens: Many converters extract raw text from the source file without reading font metadata. In a PDF, bold text isn’t flagged with a “bold” attribute — it’s rendered in a different font (e.g., “TimesNewRoman-Bold” vs “TimesNewRoman”). Converters that don’t analyze font names will lose all styling information.
How to fix it:
- Use a better converter: CheersPDF’s PDF to EPUB converter reads font name metadata for every text span and applies
<strong>,<em>, and<code>tags automatically. - Manual fix in Calibre: Open the EPUB in Calibre’s editor (Edit Book → select the EPUB), then manually add bold/italic tags to the XHTML files.
- Manual fix with Sigil: Sigil is a free EPUB editor. Open your EPUB, find the chapter files, and add
<strong>or<em>tags around text that should be styled.
Issue 2: Missing or Broken Images
What happened: The source file had images, but the EPUB shows broken image placeholders or no images at all.
Why it happens: Image extraction from PDFs requires rendering each image object to a canvas and exporting it. Some converters skip images entirely, extract them at tiny resolutions, or fail to properly reference the image files in the EPUB’s XHTML content.
How to fix it:
- Use a converter with proper image extraction: CheersPDF extracts images at their original resolution, renders them to a canvas, and exports at 92% JPEG quality for large images or lossless PNG for smaller graphics.
- Check the EPUB structure: Open the EPUB as a ZIP file (rename .epub to .zip). Look in the OEBPS/images/ folder. If images are there but not showing, the XHTML files may have broken
<img>references. - Re-add images manually: In Sigil, you can add images to the EPUB and insert
<img>tags in the appropriate chapter files.
Issue 3: Paragraphs Merged Into Walls of Text
What happened: In the source file, paragraphs were clearly separated. In the EPUB, everything runs together with no spacing between paragraphs.
Why it happens: PDF text extraction returns individual text items with X/Y coordinates, but no explicit “paragraph break” marker. Basic converters treat every line as continuous text, only breaking at page boundaries. Without analyzing the vertical gap between lines, paragraph breaks are lost.
How to fix it:
- Use a converter with gap analysis: CheersPDF measures the Y-position distance between consecutive text lines and compares it to the statistical median line gap. A gap exceeding 1.8x the typical line spacing triggers a new paragraph.
- Manual fix: Open the EPUB in Sigil and add
<p>tags to separate paragraphs. This is tedious for long documents but effective. - Calibre heuristic processing: In Calibre, enable “Heuristic processing” and the “Unwrap lines” option during conversion. This can help detect paragraph boundaries.
Issue 4: Broken or Missing Hyperlinks
What happened: The source PDF had clickable URLs, but in the EPUB they’re just plain text.
Why it happens: Hyperlinks in PDFs are stored as “annotations” — invisible rectangles overlaid on the text, each with a target URL. These annotations are separate from the text content. Converters that only extract text will miss the link annotations entirely.
How to fix it:
- Use CheersPDF: CheersPDF reads PDF link annotations, matches them to text spans by position, and wraps the linked text in
<a>tags with the original URLs. Links are sanitized to only allow http, https, and mailto protocols. - Manual fix: In Sigil, find URL text in the XHTML and wrap it in
<a href="URL">...</a>tags. - Auto-link URLs: Some EPUB editors can detect URL patterns and auto-convert them to clickable links.
Issue 5: Wrong Image Sizes
What happened: Images appear in the EPUB but are either tiny or stretched to fill the entire page, ruining the reading experience.
Why it happens: If the converter doesn’t preserve the original image dimensions, the EPUB reader has to guess the display size. Without explicit width and height attributes, images may be scaled unpredictably.
How to fix it:
- Use a converter that preserves dimensions: CheersPDF stores the original width and height of every extracted image and includes these as attributes in the EPUB’s
<img>tags, ensuring correct display. - Edit the CSS: In the EPUB’s stylesheet, add
img { max-width: 100%; height: auto; }to prevent images from overflowing while maintaining their aspect ratio. - Fix individual images: In Sigil, edit the
<img>tags to add explicit width/height attributes or inline styles.
Issue 6: No Chapter Structure or Table of Contents
What happened: The EPUB has no chapters in the table of contents — it’s just one long, continuous document.
Why it happens: The converter didn’t detect chapter boundaries in the source file, or didn’t create separate XHTML files for each chapter. Without a proper table of contents (NCX and navigation documents), ebook readers can’t show a chapter list.
How to fix it:
- Look for page-break converters: CheersPDF creates chapter breaks based on the PDF’s page count, generating a navigable chapter structure with both EPUB 3 navigation and EPUB 2 NCX compatibility.
- Add chapters in Sigil: Split the content into separate XHTML files at chapter boundaries, then update the navigation document.
- Add chapters in Calibre editor: Use Calibre’s “Edit Book” feature to split content and regenerate the table of contents.
Issue 7: Garbled Characters or Encoding Issues
What happened: Some characters appear as question marks, boxes, or completely wrong symbols in the EPUB.
Why it happens: Character encoding mismatches. The source file uses one encoding (e.g., Windows-1252) but the converter outputs UTF-8 without proper mapping. This is most common with non-English text and special characters.
How to fix it:
- Verify source encoding: If converting with Calibre, set the correct input encoding in the conversion settings.
- Check XHTML declaration: Ensure the EPUB’s XHTML files have
<?xml version="1.0" encoding="UTF-8"?>at the top. - Re-convert with UTF-8: CheersPDF outputs UTF-8 EPUB files by default, which handles all Unicode characters correctly.
Issue 8: Lists Lost Their Formatting
What happened: Bulleted or numbered lists in the source file appear as plain paragraphs in the EPUB, with bullet characters or numbers mixed into the text.
Why it happens: PDF files don’t have a “list” element. Bullets and numbers are just rendered text characters. Converters must detect list patterns (lines starting with •, –, numbers) and convert them to proper <ul>/<ol>/<li> HTML tags.
How to fix it:
- Use a smart converter: CheersPDF detects common list prefixes (bullets, dashes, numbers, letters) and converts them to proper HTML lists with the prefix character removed.
- Manual fix: In Sigil, replace paragraph tags containing list items with proper
<ul><li>...</li></ul>or<ol><li>...</li></ol>markup.
Prevention Is Better Than Cure
The best way to avoid EPUB formatting issues is to use a high-quality converter from the start. CheersPDF’s PDF to EPUB converter is specifically designed to preserve formatting by:
- Analyzing font metadata for every text span (bold, italic, monospace detection)
- Reading PDF link annotations and creating clickable hyperlinks
- Extracting images at original resolution with preserved dimensions
- Detecting paragraph breaks through Y-position gap analysis
- Recognizing list patterns and converting to proper HTML lists
- Detecting bold short lines as subheadings for better document structure
All of this happens in your browser with zero file upload, making it both the highest-quality and most private option available.
Quick tip: If you’ve already converted a file and the EPUB has issues, try re-converting the original source file with CheersPDF before attempting manual fixes. A better converter often solves the problem without any editing.
Tools for Editing EPUB Files
If you still need to manually edit your EPUB after conversion, here are the best tools:
- Sigil: Free, open-source EPUB editor for Windows, macOS, and Linux. The best option for hands-on EPUB editing with full access to XHTML, CSS, and images.
- Calibre’s Edit Book: Built into Calibre, it provides a code editor for EPUB content with preview. Good for quick fixes.
- Any text editor: Since EPUB files are ZIP archives containing XHTML files, you can rename .epub to .zip, edit the files with any text editor, and re-zip.
Common Mistakes
- Skipping the sample test and judging a workflow by one file only.
- Ignoring output fidelity until after the conversion is complete.
- Choosing a tool without checking privacy, device support, and file size limits.
FAQ
Q: What is the main benefit of this guide? A: It gives readers a direct answer and a repeatable workflow for troubleshooting.
Q: Who should use this workflow? A: It is best for readers who want a private, low-friction way to complete the task.
Q: What should I check before I start? A: Start with a clean source file, review the output, and keep the version that preserves structure and readability.
Q: Does this approach work on mobile and desktop? A: Yes, the workflow is designed to work across modern desktop and mobile browsers when the source file is supported.
Q: What should I read next? A: Read the related posts in the blog hub for comparisons, troubleshooting, and deeper guidance on fix epub formatting issues after conversion.
Conclusion
A good conversion or workflow guide should leave the reader with a clear next step, a defensible decision, and fewer unknowns than when they started. That is the standard this migration now aims to meet.
