EPUB FixerKDP upload error scanner

EPUB error guide

Check EPUB after Calibre conversion

Use this when Calibre has produced an EPUB that opens locally but still needs a stricter KDP, Kindle Previewer, or EPUBCheck pass before you edit, clean up, or convert again.

Scan EPUB structureSee an example report

Scan the EPUB to check file paths and see what can be repaired or needs manual review. Your original EPUB stays unchanged.

No signup before the scan report.Your original file is not overwritten.Repair download only after EPUBCheck passes again.

Need fixed-layout, DRM, or source-file help? Check unsupported or review-first EPUB cases.

Match these report titles

  • Check EPUB after Calibre conversion
  • Calibre EPUB failed KDP upload
  • Calibre EPUB failed EPUBCheck
  • Calibre EPUB OPF, TOC, link, image, manifest, media-type, or ZIP blocker
  • Validate Calibre EPUB before KDP upload

Start here

Check the Calibre output before assuming the conversion is valid.

Upload the EPUB Calibre produced, not the source format. The scan checks the package KDP sees, including OPF metadata, navigation, chapter links, anchors, images, CSS, manifest entries, media types, container.xml, and ZIP structure.

Matched

What it means

Calibre output is still an EPUB package. Validators inspect whether metadata, manifest entries, navigation, resources, anchors, container paths, and ZIP structure agree.

Matched

Can it be fixed automatically?

A checked repair is possible when the converted EPUB has one clear mismatch that can be checked again, such as a path, manifest item, media type, OPF field, navigation, anchor, container, or ZIP issue.

Matched

What to check next

Upload the .epub file produced by Calibre.

Matched

What not to assume

It cannot perform conversion, clean malformed source documents, remove DRM, restore missing assets, fix visual formatting, repair fixed-layout or image-first books, or decide KDP review outcomes.

1. Example report output

What a Calibre conversion report should show.

A useful report should explain what a local reader tolerated but a stricter validator may reject.

Converted file

The .epub produced or saved by Calibre.

Package checks

OPF metadata, manifest, spine, nav.xhtml, toc.ncx, links, anchors, images, CSS, container.xml, and ZIP structure.

Common blocker

Missing converted resources, stale anchors, wrong media types, disconnected navigation, or ZIP wrapper problems.

Decision

Checked repair, manual cleanup, reconversion from source, unsupported, or no supported blocker found.

The report should tell you whether one package issue is fixable or whether the Calibre conversion output needs cleanup or reconversion.

2. Next step

Choose repair, cleanup, or reconversion.

The scan should keep you from repeatedly converting without knowing which packaged file failed.

Repair package

One converted package path is wrong.

Repair may be safe for OPF, manifest, media type, navigation, path, anchor, or ZIP wiring when the target is clear.

Manual cleanup

The report names a file but the right content is unclear.

Use an EPUB editor or source tool when headings, notes, reading order, or missing assets need judgment.

Reconvert

The conversion output is the real problem.

Return to Calibre or the original source when the output is malformed, fixed-layout, image-first, or missing core content.

3. Concrete path example

A Calibre EPUB can fail because a reader tolerated a missing resource.

Local reading does not prove the package is valid for upload.

Report:
Source file: OEBPS/Text/chapter1.xhtml
Referenced image: ../Images/titlepage.jpg
ZIP target: missing
Decision: manual review; restore the image in source or reconvert with the asset included

If the resource does not exist anywhere in the EPUB, a structure repair cannot recreate it.

Quick decision

Decide whether this is a Calibre output structure issue.

Use this after Calibre has already produced an EPUB. This page does not convert files.

Good fit

You have a Calibre-converted reflowable EPUB.

The scanner can inspect OPF metadata, navigation, links, anchors, resources, manifest entries, media types, container.xml, and ZIP packaging.

Manual fit

The conversion output is messy but still inspectable.

Use the report to find the path, then clean the EPUB or source file when the fix needs judgment.

Not this tool

You need conversion, layout cleanup, or DRM work.

EPUB Fixer does not convert files, remove DRM, rebuild missing content, or redesign formatting.

Common situations

Common Calibre EPUB conversion cases.

Start with the EPUB Calibre actually produced.

Matched

The Calibre EPUB opens locally but fails KDP.

Calibre's viewer may tolerate missing paths, stale anchors, OPF issues, or ZIP rules that KDP and EPUBCheck reject.

Scan the converted EPUB and inspect the first affected path.

Matched

Images or media types do not match.

Converted files can keep stale extensions or manifest media types after format changes.

Repair only when the real file type and references are clear.

Calibre conversion phrases to check

Check EPUB after Calibre conversion: scan a Calibre-converted EPUB for KDP, Kindle Previewer, EPUBCheck, OPF, TOC, links, anchors, resources, manifest, media-type, container, and ZIP blockers.

Where Calibre EPUB blockers usually appear

A Calibre-converted EPUB opens in a reader but fails KDP, Kindle Previewer, EPUBCheck, or another stricter validation step.

What it means

A Calibre EPUB can open locally while still failing stricter upload checks.

Calibre conversion blockers often include missing images or stylesheets, rewritten anchors, stale TOC links, OPF metadata mismatches, undeclared manifest items, wrong media types, disconnected nav.xhtml or toc.ncx, container.xml mistakes, and ZIP wrapper problems.

Before you edit

Check the converted package before another conversion.

Before converting again, check whether the failure is a missing resource, broken anchor, OPF mismatch, navigation wiring issue, wrong media type, container path, or ZIP wrapper mistake.

  1. 1Upload the .epub file produced by Calibre.
  2. 2Keep the original source file and Calibre conversion settings in case the report requires reconversion.
  3. 3Check whether the report names OPF, nav.xhtml, toc.ncx, XHTML links, anchors, images, CSS, manifest entries, media types, container.xml, or ZIP packaging.
  4. 4Use checked repair only when the target path or package field is unambiguous and EPUBCheck passes again.
  5. 5Return to Calibre or the original source when the converted EPUB is missing content, fixed-layout, image-first, malformed, or visually wrong.
  6. 6Do not use this scanner for DRM removal, source conversion, broad formatting cleanup, or KDP account issues.

Why validators check it

Why Calibre output still needs EPUBCheck-style validation.

EPUBCheck

EPUBCheck checks EPUB 2 and EPUB 3 files against the official rules and reports package, markup, link, and file-reference problems.

EPUB 3.3 package rules

The OPF file is the EPUB's map: metadata, file list, reading order, and navigation wiring. KDP and EPUBCheck use it to decide whether the book package is coherent.

KDP eBook file formats

KDP supports EPUB files that meet Kindle Publishing Guidelines and recommends checking the file with Kindle Previewer before upload.

Repair example

When a Calibre EPUB issue can be repaired here.

Before / after example

Before: a converted chapter points to Images/titlepage.jpg, but the EPUB only contains images/titlepage.jpg. After: the path may be aligned when the target is unique and EPUBCheck passes again. Before: the image is absent; reconvert or restore the asset.

Ready to retry?

Upload the Calibre-converted EPUB for a structure scan.

Use the converted .epub file, not the source format. The report tells you whether the problem is a repairable package mismatch, conversion cleanup, source-format work, or an unsupported file.

Upload EPUB to scan

FAQ

Questions authors ask after Calibre EPUB conversion.

Can EPUB Fixer validate a Calibre-converted EPUB?

Yes, if you upload the converted reflowable .epub. The report can identify supported package, navigation, OPF, link, anchor, media-type, container, or ZIP blockers.

Does opening in Calibre mean the EPUB is valid?

No. Calibre or another reader can tolerate issues that KDP, Kindle Previewer, or EPUBCheck rejects. The scan checks stricter package structure.

Can this convert my file with Calibre?

No. EPUB Fixer starts after you already have an EPUB. It does not convert DOCX, PDF, MOBI, KPF, KCB, or other source files.

What if the Calibre output is missing images or chapters?

Restore the source assets or reconvert. EPUB Fixer can point to missing paths, but it should not invent missing book content.

Related EPUB error guides