Fix EPUB Formatting Problems by Finding Their Source

Where to start

First decide whether the problem comes from the manuscript, the conversion or a particular reading app. Reproduce it on a second reader and note the text size and theme. A screenshot alone rarely tells you which stage introduced the defect.

Keep the original EPUB and edit a copy. When possible, repair the source document and regenerate; repeated conversions of a damaged file can compound markup and spacing problems.

Triage the symptom

• Broken lines: inspect the source for manual line breaks, especially after PDF conversion.
• Missing chapters in navigation: check heading structure and the exporter's navigation settings.
• Huge gaps: inspect empty paragraphs, fixed spacing and forced page breaks.
• Clipped images: check fixed dimensions and whether the image can shrink to the reading area.
• Validation errors: run EPUBCheck and fix the referenced file or element before judging appearance.

Separate source defects from reader differences

If every paragraph ends after a short line on both readers, inspect the source for hard returns. If only one app changes a font, it may be applying a reader preference or handling embedded fonts differently. The first problem needs a text repair; the second needs a compatibility decision.

After a change, retest the original failing location plus a normal chapter. A global spacing fix can repair one page while making the rest cramped. Keep a small regression checklist: opening, chapter jump, long paragraph, image, footnote and ending.

Check your result

• The original failure is gone on the affected reader.
• The correction does not create a new defect elsewhere.
• EPUBCheck issues are resolved or understood.
• The repaired source can reproduce the final file.

References and scope

Reference material checked October 28, 2026. The exercises and examples are editorial guidance, not results from a comparative product test. EarnDraft publishes this guide and sells book-creation software.

EPUBCheck