A quick EPUB check before upload can prevent distributor rejection and reader-facing problems. Validate structure, navigation, and metadata together, then upload one clean final file.
Start with your newest EPUB only
Always validate the latest export, not an older file from an earlier draft.
If chapter order, heading structure, front or back matter, or metadata changed, treat the EPUB as a new file and rerun the checks.
Use clear file names so you always know which EPUB you just tested.
Check structure and navigation before styling details
Open the EPUB in at least one reader and click through the table of contents from top to bottom.
Check chapter order, where chapters begin, and where back matter appears before worrying about cosmetic warnings.
If the structure is wrong, smaller visual fixes are not your main problem yet.
Check metadata in the same pass
Make sure title, author name, language, and identifier are correct for this edition.
Metadata problems can hurt storefront quality even when the book looks fine on screen.
If metadata changes, rerun both the validator and the TOC checks on the new export.
Separate stop-sign problems from minor warnings
If the TOC is broken, links fail, or required metadata is missing, stop and fix those problems before upload.
If a warning affects reading order, navigation, or visible rendering, fix it before you distribute the file.
Only minor advisory warnings should ever move forward, and only if you understand why they are safe.
Fix the source file, export again, and validate again
Make fixes in the source manuscript or export settings, then generate a fresh EPUB.
Avoid editing the EPUB package directly as your normal workflow. That usually drifts away from the source file and makes future updates harder.
Repeat the validator and the click-through checks until one EPUB passes the way you want it to.
Numbers and Reference Tables
EPUB Validation Triage Matrix
Issue class
Example signal
Source-first action
Release decision
Navigation or TOC error
TOC jump lands on the wrong chapter or a missing target
Clean up heading hierarchy and anchor-producing headings in the source file
Do not upload until fixed
Broken internal link
Back matter link or chapter cross-reference fails
Repair link targets in the source file and export again
Do not upload until fixed
Metadata defect
Missing or invalid language or identifier field
Correct metadata fields and regenerate the EPUB
Do not upload until fixed
Rendering warning
Unsupported CSS affects readability
Simplify style usage and verify in multiple readers
Fix before upload if readers can see the problem
Advisory-only warning
A non-critical best-practice notice
Document why it is safe and run extra device QA
Proceed only if you understand the tradeoff
Publish Checklist
Export one EPUB from the latest manuscript source.
Verify chapter order and front/back matter order in a reader.
Click every TOC entry and confirm the destination is correct.
Confirm title, author name, language, and identifier metadata.
Run EPUB validation on that exact file.
Sort findings into stop-sign problems, rendering warnings, or minor advisories.
Fix stop-sign problems and visible structural warnings in the source file.
Export again and rerun validation on the new EPUB.
Run TOC and internal-link checks again after fixes.
Test in at least two reading environments before upload.
Upload only the validated EPUB and keep that exact file.
Warning-to-Fix Map
Warning pattern: navigation document missing or invalid
Fix: Rebuild chapter heading structure in the source file and regenerate the EPUB with a complete navigation document.
Verify: Validator confirms the navigation document is present and valid.
Warning pattern: TOC entry lands on the wrong chapter
Fix: Remove duplicate heading targets and normalize chapter heading hierarchy.
Verify: Every TOC link lands on the intended chapter heading.
Warning pattern: duplicate id or anchor target
Fix: Make sure each chapter and major section heading has one unique target in the source content.
Verify: Validator no longer reports duplicate identifiers.
Warning pattern: broken internal hyperlink
Fix: Correct link targets in the source front matter, back matter, and chapter references.
Verify: All internal links work in reader click-through checks.
Warning pattern: malformed metadata field
Fix: Clean up title, author, language, and identifier values before exporting again.
Verify: Validator reports no required metadata field errors.
Warning pattern: unsupported CSS or rendering warning
Fix: Simplify source styles and remove unsupported properties that affect reader rendering.
Verify: Warning count drops and layout stays stable in at least two readers.
Warning pattern: chapter order looks correct but TOC is stale
Fix: Regenerate the TOC from the current heading structure before exporting again.
Verify: TOC order and chapter order both match the manuscript.
Warning pattern: issue remains after fix
Fix: Make sure validation is running against the newest export and remove stale local files.
Verify: The newly named EPUB passes the same validation step.
The Senswriter way (faster)
Use the same workflow in one workspace: draft, export, run checks, fix the source, and upload one clean final file.
Write and reorganize chapters/scenes without switching between multiple tools.
Generate print-ready PDF, EPUB, and DOCX from the same manuscript source.
Re-export quickly after fixes so KDP and EPUB checks stay repeatable.
Use optional BYOK AI assist only if you want drafting support.