Uses the file you retry
Upload the exported .epub that failed. The scan follows package files, links, anchors, and metadata inside that exact file.
See whether your failed EPUB can be repaired before you upload again.
Your EPUB opens in a reader, but KDP, Kindle Previewer, or EPUBCheck still rejects it?
KDP upload errorsKindle Previewer messagesEPUBCheck codes
Example scan report
3 upload blockers found
Second EPUBCheck
Passed
Repairable
2
Manual review
1
Download
Ready
RSC_007Missing image targetManual review
OPF_030Unique identifierRepairable
PKG_006Mimetype orderRepairable
EPUBCheck passed againRepaired EPUB available
Use the upload when the EPUB itself failed KDP, Kindle Previewer, or EPUBCheck. EPUB Fixer follows the package paths in that file, stops before changing book decisions, and only shows a repaired download after another EPUBCheck pass.
Names the failing path
The report points to the OPF, nav.xhtml, chapter, image, stylesheet, anchor, or manifest entry behind the upload blocker.
Stops before guessing
If the next move depends on reading order, headings, images, or layout, the report stops at manual review.
Checks again before download
A repaired EPUB appears only after the written structure change passes another EPUBCheck run.
Start here
Choose based on what you have right now.
You do not need to know the EPUB internals first. Start from the file, the error text, or the sample report.
I have the EPUB file
Upload the file you plan to retry.
Use this when KDP, Kindle Previewer, or EPUBCheck already rejected the exported .epub.
I only have the error text
Find the closest error guide first.
Use this when you have RSC_007, RSC_012, OPF_030, PKG_006, or a Kindle Previewer message.
I want to see the output
Preview the report before using your file.
Use this to see affected paths, repair status, and download boundaries before uploading.
Checked repair proof
A repaired EPUB appears only after the second EPUBCheck pass.
If that second check does not pass, the report still explains the problem, but no repaired download appears.
Detect the failing package part
The scan names the package path, manifest entry, anchor, or identifier behind the upload blocker before you edit anything.
Write only clear structure changes
Checked repairs stay inside package wiring such as manifest entries, media types, identifiers, navigation links, or ZIP structure.
Hold the download until EPUBCheck passes again
If the second EPUBCheck run still reports issues, the report stays in explanation mode and no checked download appears.
EPUB 3.3 package structure
An EPUB includes chapter files, metadata, a file list, reading order, navigation files, and a ZIP container. These parts must line up for upload checks to pass.
EPUBCheck conformance checking
EPUBCheck reports rule errors. EPUB Fixer uses those messages to separate simple fixes from issues that need a person to decide.
KDP EPUB upload expectations
KDP accepts EPUB files that meet Kindle Publishing Guidelines and recommends checking them in Kindle Previewer first. EPUB Fixer is for errors found in that step.
Coverage matrix
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 entries or media types when the correct file already exists
- Package identifier wiring such as OPF unique-identifier links
- Navigation or NCX wiring when one clear target already exists
- ZIP package issues such as mimetype order when the correct fix is clear
Needs manual review
- Broken anchors when several headings or notes could be the intended target
- Reading-order or TOC fixes that depend on author intent
- Missing files, damaged images, or malformed chapter content
- Cases where the scanner can explain the problem but should not choose the fix
Out of scope
- DOCX, PDF, KPF, or KCB conversion
- Fixed-layout, comics, DRM-protected, or image-first EPUBs
- Book formatting, layout redesign, or prose changes
- KDP account, listing, pricing, tax, or review workflow issues
Common KDP blockers
Match the exact EPUBCheck or KDP error text.
Paste the code or compare the message. Most EPUB errors point to a missing file, broken link, bad metadata entry, or packaging problem.
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_006mimetype file entry is missing or not first
Use this when the EPUB was zipped incorrectly, often after manual zipping or archive-tool changes.
Common EPUB structure checks
Start with the part of the EPUB that failed.
These entry points all use the same scanner and result page. They only set the default report focus.
Broken links and missing anchors
Use this when EPUBCheck points to RSC_007, RSC_012, missing images, stale chapter links, or anchors after # that no longer exist.
TOC and navigation wiring
Use this when KDP or Kindle Previewer says the table of contents is missing, nav.xhtml is not declared, or toc.ncx is disconnected.
Manifest and media-type problems
Use this when a file exists but is missing from the OPF manifest, or content.opf declares the wrong media type for an existing file.
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 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 safe 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 the fix is safe.
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. EPUB Fixer does not rewrite prose, redesign pages, or guess what the book should say. It only fixes clear EPUB package problems such as file lists, reading order, navigation, table of contents, or ZIP packaging.
Is my uploaded EPUB stored permanently?
No. The upload is temporary scan input. EPUB Fixer does not show manuscript text in the report, lets you delete the upload after scanning, and removes expired uploads automatically.
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?