What failed
Shows the OPF, XHTML, nav, NCX, image, CSS, or package entry tied to the validation error.
Example report
Preview the EPUB scan report before uploading your file.
See the kind of answer you get before you upload an unpublished EPUB. This fictional sample shows paths, plain-English notes, and next steps without using a real file or manuscript text.
Before you upload
Know what the report will actually show.
Use this page to decide whether the scan output is useful for your KDP, Kindle Previewer, or EPUBCheck problem.
Can it be fixed safely?
Separates automatic fixes from manual review and EPUB types this scanner should not change.
Privacy boundary
The report uses paths and error summaries. It does not display manuscript text in the sample or result view.
What to look at first
Start with the affected path and next step.
A useful scan report should tell you where the error lives and whether changing the EPUB package is safe without guessing the book's intended content.
- Path: the OPF, XHTML, nav, NCX, image, CSS, or package entry connected to the error.
- Safe-fix note: whether the change can be made and pass EPUBCheck again.
- Next step: what to check before another KDP or Kindle Previewer upload attempt.
Statusaccepted
Safe fix1
Manual review1
Not supported1
Before / after validation
See how the report moves from error to decision.
The important part is not just whether an error exists. It is whether the EPUB can be safely changed, left for manual review, or stopped before a risky edit.
Before
EPUBCheck reports the original blocker.
ERROR(RSC-007): OEBPS/Text/chapter-03.xhtml(44,19): Referenced resource "../Images/map.png" could not be found in the EPUB.
Fix decision
The report separates safe repair from manual review.
Manual review: the missing image has no single clear replacement target. Safe repair: only offered when the package contains one obvious target and the repaired file can be checked again.
After
The next state is explicit.
Manual review issues stay unchanged with a path to inspect. Safe repairs show a download only after the repaired EPUB passes EPUBCheck again.
Repair boundary
The scanner should not guess what your book should contain.
This is the boundary to check before trusting any automatic repair. If the correct change requires editorial judgment, the report stops at diagnosis.
- No manuscript text shown in the report.
- No layout rewrite or visual redesign.
- No guessed chapter, anchor, or image replacement.
- Download appears only after EPUBCheck passes again.
Example findings
Each issue ends with a practical next step.
A real report includes the affected file path inside the EPUB, a plain-English summary, a safe-fix note, and a next step for each issue.
OPF_030 unique identifier not found
The package metadata does not point to a clear unique identifier.
Source pathOEBPS/content.opf
Original messageERROR(OPF-030): OEBPS/content.opf(-1,-1): The unique-identifier "uid" was not found.
KDP / Previewer wordingKDP or Kindle Previewer may describe this as invalid package metadata instead of showing OPF_030.
Triggerpackage unique-identifier points to id="uid", but no matching dc:identifier id exists
Evidenceone UUID-style dc:identifier is present and no competing ISBN or retailer id is packaged
DecisionSafe to repair if that UUID is the intended publication identifier.
Next stepDownload appears only if the repaired file passes EPUBCheck again.
AvoidDo not create a new ISBN, UUID, or retailer id just to clear the validator message.
RSC_007 referenced resource could not be found
A chapter points to an image path that is not present in the EPUB package.
Source pathOEBPS/Text/chapter-03.xhtml
Original messageERROR(RSC-007): OEBPS/Text/chapter-03.xhtml(44,19): Referenced resource "../Images/map.png" could not be found in the EPUB.
KDP / Previewer wordingKDP may say the EPUB has a missing resource, broken image, or content validation error.
Triggerimage src points to ../Images/map.png
Evidenceno single matching image file exists in the EPUB package
DecisionNot safe to invent or replace the missing image automatically.
Next stepCheck the affected XHTML file or ask a formatter to restore the missing resource.
AvoidDo not delete the image reference unless you know the image is not part of the book.
Fixed-layout metadata detected
The EPUB declares pre-paginated layout metadata.
Source pathOEBPS/content.opf
Original messagePreflight check: OPF metadata declares rendition:layout as pre-paginated.
KDP / Previewer wordingKindle Previewer may still open fixed-layout pages, but structural auto-repair is not safe here.
Triggerrendition:layout is set to pre-paginated
Evidencefixed-layout pages need visual and editorial review
DecisionOutside this scanner because automatic structural edits can damage page design.
Next stepUse the original design/export tool or a fixed-layout specialist instead of this scanner.
AvoidDo not remove fixed-layout metadata to force a reflowable repair path.