Find the failing path
The scan names the package path, manifest entry, anchor, or identifier behind the upload blocker.
KDP upload failure · Kindle Previewer message · EPUBCheck code
Check whether your EPUB upload error can be safely repaired.
Upload the exact .epub that failed. The report names the affected path, separates checked repairs from manual work, and only offers a repaired copy after the file passes the checks again.
What the report answers
Preview a sample report- Affected path
- The OPF, navigation, chapter, image, stylesheet, or package entry behind the failure.
- Repair boundary
- Repairable, manual review, or out of scope—with no guessed book decisions.
- Download gate
- A separate copy only after the written repair passes the structure scan and EPUBCheck again.
Download safety gate
A repaired copy appears only after both post-repair checks pass.
If either check still reports a problem, the report explains the next step but no download appears.
Write one clear structure fix
A repair is written only when the correct package change is deterministic and does not require a book decision.
Run the structure scan and EPUBCheck again
The separate copy becomes downloadable only after both post-repair checks pass.
Repair limits
See what this scanner can repair, what it will only explain, and what it will reject.
This is not a general-purpose EPUB service. It only writes changes when the correct structure fix is clear and verifiable.
Can repair
- Manifest, media-type, and identifier wiring when the correct target already exists
- Navigation, NCX, and cover metadata when one existing target is clear
- ZIP package issues such as mimetype order when the fix is deterministic
Needs manual review
- Broken anchors with several possible targets
- Reading order or TOC changes that depend on author intent
- Missing or damaged assets, cover image warnings, or malformed chapter content
Out of scope
- DOCX, PDF, KPF, or KCB conversion; fixed-layout, comics, DRM-protected, or image-first EPUBs
- Cover image editing; book formatting, layout redesign, or prose changes
- KDP account, listing, pricing, tax, review workflow, multimedia, or script issues
Common KDP blockers
Have an error code? Start with the exact match.
Compare your code or message with these common blockers. If none matches, open the full error guide index.
RSC_005duplicate ID in XHTML
Use this when EPUBCheck reports duplicate ids after export or editing, especially around footnotes, headings, backlinks, or TOC anchors.
RSC_007referenced resource could not be found
Use this when KDP or EPUBCheck says an image, stylesheet, chapter, table of contents file, or other referenced file is missing.
RSC_012fragment identifier is not defined
Use this when a link points to a note, heading, anchor, or table of contents target that no longer exists.
OPF_030unique-identifier was not found
Use this when the EPUB package points to a book identifier that is missing from the metadata.
PKG_006:EPUB mimetype missing or not first
Use this when the EPUB was zipped incorrectly, often after manual zipping or archive-tool changes.
FAQ
Short answers before you upload.
Can EPUB Fixer repair every KDP upload error?
No. It only fixes cases where the correct change is clear. If the fix would require choosing chapter order, rewriting text, picking a heading, or redesigning layout, the report stops at diagnosis.
When can I download a repaired EPUB?
Only when the file is supported, the change is automatic, and the repaired EPUB passes the structure scan and EPUBCheck again. Retry the downloaded file in KDP or Kindle Previewer before treating it as final.
Is this a DOCX to EPUB converter?
No. Upload an existing EPUB 2 or EPUB 3 book. EPUB Fixer does not turn DOCX, PDF, KPF, KCB, ZIP archives, fixed-layout books, comics, or image-first books into EPUB.
Is EPUB Fixer free to use?
Yes. You can scan an EPUB for free. If a checked repaired copy is available, the result page shows a download while the upload is still available.
What EPUB versions are supported?
EPUB Fixer works best with normal text-first EPUB 2 and EPUB 3 books. It does not handle fixed-layout books, comics, DRM-protected files, KPF, KCB, complex multimedia, or heavily scripted EPUBs.
How is this different from EPUBCheck?
EPUBCheck tells you which part failed its check. EPUB Fixer turns that message into a next step and only offers a repaired copy when one deterministic structure change passes the structure scan and EPUBCheck again.
Can I fix an EPUB online with this tool?
Yes when the issue is a clear EPUB structure problem. Upload the EPUB, check the report, and download a repaired file only if the automatic repair passes both post-repair checks. Missing content, layout, cover design, and conversion still need another workflow.
Which publishing platforms can these errors affect?
KDP and Kindle Previewer are the main focus. If another upload checker shows the same EPUBCheck-style structure error, use the report to compare the affected path before changing the file.
Why does an EPUB open locally but fail KDP?
Reading apps such as Calibre can be forgiving. KDP, Kindle Previewer, and EPUBCheck are stricter about package files, navigation, anchors, media paths, metadata, and ZIP packaging.
Does the scan change my manuscript?
No. The scan does not modify your original EPUB. When one deterministic repair is available, EPUB Fixer creates a separate copy without rewriting prose, redesigning pages, or guessing what the book should say.
Is my uploaded EPUB stored permanently?
No. The original EPUB, repaired copy, and temporary scan files are deleted automatically after 24 hours. You can delete those files sooner from the result page; scan metadata and saved follow-up records have a separate lifecycle explained on the Privacy page.
What is the maximum EPUB file size?
Upload one .epub file that is 30 MB or smaller. Larger files, ZIP archives, PDFs, DOCX files, and source project files are rejected before scanning.
Ready to retry?