Have the exact EPUBCheck code?
Open the matching RSC, OPF, or PKG guide first. It tells you which file path, anchor, metadata field, or package rule to inspect before changing the EPUB.
Fix supported EPUB errors for Kindle, KDP, or Apple Books
Have a finished EPUB that Kindle, KDP, Apple Books, EPUBCheck, or a distributor rejected? Choose the closest error guide, or upload the file when you need the affected path and whether a checked repair is possible.
Error text matcher
Paste the exact error line.
Check whether this looks like your EPUB error. Upload only when you need the exact file path and repair decision.
Paste one KDP, Kindle Previewer, or EPUBCheck error line.
Waiting for error text
- Likely guide
- The closest EPUBCheck, KDP, or Kindle Previewer guide.
- Affected area
- Path, anchor, OPF field, navigation, or ZIP packaging clue.
- When to upload
- Upload when you need the report to name the real EPUB path and next step.
- 1Choose the situationStart with a Kindle, KDP, Apple Books, or EPUBCheck message, a pre-upload check, or the exact error text already on screen.
- 2Open the guideCheck the likely KDP, Previewer, EPUBCheck, path, anchor, OPF, navigation, cover, manifest, or ZIP packaging cause.
- 3Scan if it is vagueUpload the EPUB when the message does not name the affected file, anchor, OPF field, or ZIP packaging rule.
Find the right guide
Common matching phrases.
Open the guide when your error contains one of these phrases. Use the paste matcher above when the wording is close but not exact.
- How to validate EPUB before uploading to KDP, validate EPUB before KDP upload, or KDP pre-upload EPUB checkKDP pre-upload validation
- EPUB check before Kindle upload, check EPUB before Kindle Previewer, or Kindle upload EPUB structure checkKindle upload check
- EPUBCheck online free, online EPUBCheck, free EPUBCheck validator, or EPUBCheck online scannerEPUBCheck online
- Free EPUB validator, online EPUB checker, validate EPUB, or check EPUB for errorsEPUB validator
- EPUB repair, repair EPUB, fix EPUB online, or checked EPUB structure repairChecked repair
- Fix EPUB for Kindle, Kindle EPUB fixer, Kindle EPUB fix online, or Kindle Previewer EPUB repairKindle EPUB repair
- Fix EPUB for Apple Books, Apple Books EPUB fix, or Apple Books EPUB validationApple Books EPUB repair
- KDP ebook formatting error, upload failed, or Kindle Previewer validation problemKDP upload failed
- EPUB opens locally but fails KDP, Kindle Previewer, or EPUBCheckReader vs validator
- EPUB cover not showing, Kindle cover missing, or OPF cover-image problemEPUB cover
- EPUB 3 cover image is missing the cover-image propertyCover-image property
- DOCX to EPUB export, Word to EPUB output, or exported EPUB failed KDPAfter export check
- Vellum EPUB export failed KDP, validate Vellum EPUB, or check EPUB after Vellum exportVellum export check
- Atticus EPUB export failed KDP, validate Atticus EPUB, or check EPUB after Atticus exportAtticus export check
- InDesign EPUB export failed validation, check EPUB after InDesign export, or InDesign EPUB KDP errorInDesign export check
- Reedsy EPUB export failed KDP, validate Reedsy EPUB, or check EPUB after Reedsy exportReedsy export check
- Scrivener EPUB export failed KDP, validate Scrivener EPUB, or check EPUB after Scrivener exportScrivener export check
- Calibre EPUB conversion failed KDP, EPUB opens in Calibre but fails validation, or check EPUB after Calibre conversionCalibre conversion check
- EPUBCheck errors, EPUBCheck online, or RSC / OPF / PKG validation messagesEPUBCheck error codes
- RSC_005 error while parsing file, EPUB XHTML parse error, named entity, XHTML namespace, or XML encoding problemXHTML parse errors
- MED_011, MED_012, MED_013, MED_014, MED_016, MED_017, MED_018, media overlay, SMIL, or media:duration errorMedia overlay errors
- Invalid EPUB file, corrupt EPUB, damaged EPUB, duplicate ZIP entry, corrupted ebook, or not a valid EPUBInvalid EPUB
- Kindle Previewer failed, conversion failed, enhanced typesetting failed, or EPUB validation failedPreviewer conversion
- EPUB metadata checker, OPF metadata error, unique identifier, manifest item missing id or media-type, duplicate manifest entry, or package media:duration errorMetadata checker
- E20006: More than one title defined in OPF metadataDuplicate OPF title
- Apple Books or Google Play rejected EPUBStore rejection
- Draft2Digital, Smashwords, Kobo, Barnes & Noble Press, or IngramSpark rejected EPUBDistributor rejection
- RSC_005: Duplicate ID in an XHTML fileRSC_005 duplicate id
- RSC_007: Referenced resource could not be found in the EPUBRSC_007 missing resource
- RSC_012: Fragment identifier is not definedRSC_012 broken anchor
- Broken internal links, internal links with missing anchor, missing files, or missing anchorsBroken links and anchors
- EPUB table of contents, nav.xhtml, toc.ncx, NCX docTitle, spine toc, or NAV_003 page-list is missingTOC and navigation
- EPUB navigation document or nav.xhtml is missingMissing nav document
- nav.xhtml is not declared in the OPF manifest or is missing properties navnav.xhtml OPF wiring
- OPF file not found in the EPUBOPF_002 package path
- RSC_003: No rootfile tag was found in container.xmlRSC_003 rootfile
- OPF_019: Spine tag was not found in the OPF fileOPF_019 spine
- OPF_030: The unique-identifier was not foundOPF_030 metadata
- dcterms:modified metadata is missing, duplicated, or malformeddcterms:modified metadata
- OPF_003 / RSC_008: referenced resource is not declared in the OPF manifestOPF_003 / RSC_008 manifest item
- RSC_011: Referenced resource is not a spine itemTOC target not in spine
- NCX_001: NCX identifier does not match OPF unique identifierdtb:uid mismatch
- NCX_002: NCX is not linked from the spine toc attributeNCX spine toc wiring
- Manifest media-type does not match the file extensionOPF_029 media-type mismatch
- PKG_021: Corrupted image file encounteredPKG_021 image
- PKG_022: Wrong file extension for imagePKG_022 image extension
- OPF_010: Error resolving referenceOPF path resolution
- PKG_006: Mimetype file entry is missing, compressed, nested, or is not the first filePKG_006 ZIP packaging
- PKG_007: Mimetype file contents are invalid or compressedPKG_007 mimetype
- PKG_010: Filename contains spaces or URI escaping is necessaryPath case / URL encoding
- PKG_009: Filename contains forbidden characters, PKG_011: filename ends with a period, or EPUB filename needs normalizationEPUB filename rules
- Kindle Previewer reports EPUB validation errorsKindle Previewer report
- Kindle conversion or enhanced typesetting failedPreviewer conversion failure
Choose your path
Pick the guide based on what you have.
Some people arrive with an EPUBCheck code. Others only have a KDP upload message. Either way, the next step is to find the affected path before guessing at a fix.
Only have a KDP or Kindle Previewer message?
Use the message matcher first. If the wording is vague, scan the EPUB so the report can point to the affected path instead of making you re-export blindly.
Not sure if it can be fixed safely?
Upload the actual EPUB to separate automatic fixes, manual checks, and problems that are outside EPUB structure repair.
Guide shortcuts
Jump to the error family.
Use these shortcuts when the paste matcher does not give you one clear guide.
Find the error you see
High-volume EPUB search entries
Start here if you searched for a Kindle EPUB fixer, Apple Books EPUB validation, EPUBCheck online, KDP upload failure, or an EPUB exported from a writing or layout tool and still have the final EPUB file to scan.
- Validate EPUB before KDP upload
Upload the finished reflowable EPUB before KDP sees it, then check for EPUBCheck, Kindle Previewer, OPF, TOC, link, manifest, cover wiring, or ZIP blockers.
- Fix EPUB for Kindle Upload and Previewer Errors
Upload the EPUB that Kindle Previewer or KDP rejected. The report finds the affected path and offers a checked repair when one safe EPUB structure fix passes EPUBCheck again.
- EPUBCheck online free for KDP preflight
Upload one reflowable EPUB for a free browser-based EPUBCheck-style scan before KDP, Kindle Previewer, or another publishing upload.
- Free EPUB validator for KDP upload errors
Upload a finished reflowable EPUB when you need a free online check for KDP, Kindle Previewer, or EPUBCheck blockers before another publishing retry.
- KDP EPUB upload failed and formatting errors
Scan the same EPUB that failed KDP upload or Kindle Previewer when the message mentions formatting, TOC, navigation, metadata, links, or validation.
- EPUB cover not showing
Scan the same EPUB when its cover is missing in Kindle Previewer, KDP, or a reader. Check whether the OPF metadata, manifest image, cover-image property, and packaged file point to one clear cover.
- Check exported EPUB after Word or DOCX workflow
Use this after a DOCX, Word, Atticus, Vellum, Reedsy, Kindle Create, or InDesign workflow has already exported an EPUB and you need to check why that EPUB may fail KDP, Kindle Previewer, or EPUBCheck.
- Check EPUB after Vellum export
Scan a Vellum EPUB before upload to check TOC links, OPF data, cover metadata, manifest entries, and ZIP packaging for KDP, Previewer, or EPUBCheck blockers.
- Check EPUB after Atticus export
Use this when you have an Atticus EPUB and need to know whether the exported file has a KDP, Kindle Previewer, or EPUBCheck blocker before you change headings, images, notes, or export settings.
- Check EPUB after InDesign export
Scan an InDesign reflowable EPUB to check generated XHTML, CSS, image paths, TOC wiring, OPF entries, media types, and ZIP packaging before upload.
- Check EPUB after Reedsy export
Use this when you have the EPUB Reedsy exported and want to know whether the final file has a KDP, Kindle Previewer, or EPUBCheck blocker before you edit the book or export again.
- Check EPUB after Scrivener export
Scan a Scrivener-compiled EPUB to check generated chapters, anchors, front matter, TOC targets, OPF metadata, manifest entries, cover wiring, and ZIP packaging.
- 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.
- EPUBCheck errors: find the affected file and next step
Keep the exact EPUBCheck code, message, and path. Use them to separate missing resources, OPF or NCX wiring, ZIP packaging, and XHTML parse errors before you change the EPUB.
- Invalid, corrupt, or damaged EPUB file
Scan when an EPUB is invalid, corrupt, unreadable, or contains duplicate ZIP entries. Check whether the wrapper can be repaired before replacing the whole export.
- Kindle Previewer conversion failed
Scan the EPUB that Kindle Previewer could not process when conversion fails, enhanced typesetting stops, or Previewer reports validation, TOC, metadata, link, anchor, or package problems.
- Fix EPUB for Apple Books or Google Play Rejection
Upload the EPUB that Apple Books rejected. The report separates a standard EPUB structure blocker from an Apple Books workflow issue and offers a checked repair only when the fix is clear.
- Draft2Digital, Kobo, B&N, or IngramSpark EPUB rejected
Use this when Draft2Digital, Smashwords, Kobo Writing Life, Barnes & Noble Press, or IngramSpark rejects an EPUB and you need to know whether the file has a standard EPUB structure blocker before another upload.
Find the error you see
Broken references and anchors
Start here when EPUBCheck or KDP points to a missing image, stylesheet, chapter file, internal link with a missing anchor, broken link target, or duplicate XHTML id.
- EPUB broken links and missing anchors
Scan when KDP, Previewer, or EPUBCheck says an EPUB link, image, stylesheet, chapter path, nav.xhtml entry, NCX target, or anchor is broken.
- Referenced resource could not be found or OPF_010
Scan when an EPUB resource cannot be found or a packaged filename breaks OCF rules. Match the source reference, real ZIP path, and dependent links before renaming anything.
- RSC_007 referenced resource could not be found
Use this when you already have the exact RSC_007 line. Follow the source file and missing target path before you change nav.xhtml, content.opf, chapters, images, or CSS.
- RSC_012: fragment identifier is not defined
Use this when an EPUB link reaches the right XHTML file but the anchor after # is missing. Check the file, the missing id, and where the reader should land before changing the link.
- EPUBCheck RSC-005 duplicate ID
Use this page only when the full RSC_005 message names a duplicate id. The scan can preserve the file, line, and error evidence, but choosing which id to rename remains manual.
Find the error you see
Package and metadata errors
Start here when the EPUB package cannot be opened cleanly, container.xml points to the wrong OPF file, metadata identifiers do not line up, images are mislabeled, or the mimetype file was zipped in the wrong place.
- OPF_030: EPUB unique identifier was not found
Use this when EPUBCheck says the EPUB unique identifier was not found. The scan checks the package unique-identifier value against the dc:identifier entries in content.opf.
- EPUB metadata checker
Use this when content.opf has a metadata or file-list error, including identifiers, modified date, incomplete manifest items, duplicate entries, missing feature properties, or media:duration totals.
- dcterms:modified missing in EPUB
Use this when EPUBCheck, Kindle Previewer, or a publishing platform points to missing, duplicated, or malformed dcterms:modified metadata in the OPF package file.
- More than one title in OPF metadata (E20006)
Use this when EPUBCheck finds more than one book title inside the EPUB package. Compare the title values before removing anything; changing the KDP listing does not change content.opf.
- OPF_029: EPUB media type does not match the file
Use this when EPUBCheck says a file does not match its declared media type. The scan compares content.opf with the file path and extension, then shows whether only the manifest needs to change.
- PKG_021 corrupted image file encountered
Use this when EPUBCheck reports PKG_021 or says a corrupted image file was encountered. Locate the packaged image before editing OPF or rebuilding the EPUB.
- PKG_022 wrong file extension for image
Use this when EPUBCheck reports PKG_022 or says an image has the wrong file extension. Compare the packaged image bytes, extension, and OPF manifest media type.
- OPF_003 or RSC_008 item is not declared in the OPF manifest
Scan when EPUBCheck, KDP, or Previewer says an EPUB resource is not declared in the OPF manifest, or when nav.xhtml exists but is not wired as navigation.
- OPF_048 package is missing unique-identifier
Use this when the OPF package tag has no unique-identifier. Check whether one real dc:identifier should identify the book before you edit the metadata.
- OPF_049 item id was not found in the manifest
Use this when an OPF reference names a manifest id that does not exist. Find where the missing id is used before you change spine or navigation wiring.
- EPUB cover-image property is missing
Use this when the EPUB cover image exists but the OPF manifest does not mark it with the EPUB 3 cover-image property.
- PKG_007 mimetype file contents invalid or compressed
Use this when the EPUB mimetype file contents are wrong or the file is compressed. Check the ZIP wrapper before you touch chapters, OPF, or navigation files.
- OPF_002 OPF file not found in the EPUB
Use this when EPUBCheck reports OPF_002, container.xml points to an OPF path the EPUB does not contain, or when the rootfile path is wrong. Find the real package file before you change the rootfile path.
- RSC_002 container.xml missing in EPUB
Use this when KDP or EPUBCheck reports RSC_002, META-INF/container.xml is missing, or the container map is not usable. Confirm the real OPF package path before rebuilding the EPUB container map.
- RSC_003 no rootfile tag in container.xml
Use this when EPUBCheck says container.xml has no rootfile tag. Check the EPUB package map before you edit chapters, metadata, or KDP settings.
- OPF_019 spine tag was not found
Use this when EPUBCheck reports OPF_019, failed handling EPUB spine item, or says the OPF spine is missing. Check the package reading order before changing nav.xhtml, toc.ncx, or chapter files.
- EPUB mimetype file missing or not first (PKG-006)
If EPUBCheck reports that the mimetype file entry is missing or is not the first file in the archive, scan that EPUB before zipping it again. The report checks the root entry order and separates PKG-006 from PKG-007 content or compression errors.
What the report will tell you
Use the report label to decide the next action.
Either fix it automatically, review the affected file by hand, or stop because the problem is not an EPUB structure issue.
- Automatic fixThe report found one clear package, metadata, reference, or container change and checks the repaired EPUB again before download.
- Manual checkOpen the affected file because the right change depends on the book's intended content or reading order.
- Not supportedUse the source tool, EPUB editor, or KDP workflow because the issue is outside EPUB structure repair.
If this is not a structure error
Use the source tool or KDP workflow instead.
- Have a DOCX, PDF, KPF, KCB, or ZIP archive? Export a real .epub before using this scanner.
- Have a fixed-layout, comic, picture book, manga, or image-first EPUB? Use the source design tool or a specialist workflow.
- Have a cover design, crop, white-border, compression, paperback PDF, spine, bleed, barcode, or Canva export problem? Fix that in the cover or design workflow instead.
- Need Send to Kindle conversion, Apple Books app/device troubleshooting, DRM removal, cover artwork changes, typography, book formatting, or KDP account help? That work happens outside the EPUB structure scan.