What gets checked
It checks the parts KDP usually cares about: file list, reading order, navigation, links, images, stylesheets, anchors, metadata, and EPUBCheck messages.
EPUB error checker
Check whether your EPUB upload error can be safely repaired.
Got an EPUB that opens fine but KDP, Kindle Previewer, or EPUBCheck rejects it?
Upload the .epub to find broken file paths, links, metadata, or packaging issues. If EPUB Fixer can repair it, the download appears only after the file passes EPUBCheck again.
Existing .epub filesShows broken pathsNo text or layout changes
For authors and ebook formatters stuck on an EPUB that looks okay locally but fails the upload check.
Your upload is temporary. The report does not display manuscript text, and you can delete the file after scanning.
Before upload
Start with the EPUB you plan to retry.
Upload the .epub you plan to retry. DOCX, PDF, and Kindle Create files need to be converted before this tool can help.
See an example first
The sample report shows what you get before you upload your own book: automatic fixes, manual checks, and unsupported cases.
Know what happens to the upload
Your EPUB is temporary. The report does not show manuscript text, and a repaired download only appears after the fixed file passes EPUBCheck again.
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_007 referenced 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_012 fragment 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_030 unique-identifier was not found
Use this when the EPUB package points to a book identifier that is missing from the metadata.
PKG_006 mimetype file entry is missing or not first
Use this when the EPUB was zipped incorrectly, often after manual zipping or archive-tool changes.
Why KDP rejects it
It checks the EPUB file, not your writing or layout.
KDP does not just read the chapters. It also checks the files around them: navigation, metadata, links, images, stylesheets, and the ZIP packaging.
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.
EPUBCheck vs EPUB Fixer
EPUBCheck gives the error. EPUB Fixer explains the next move.
It keeps the decision simple: retry as-is, fix something by hand, or download a repaired copy when the change is safe.
EPUBCheck finds the error
EPUBCheck tells you which part of the EPUB failed its check. The raw message can still be hard to connect to the file you need to inspect.
EPUB Fixer explains the next action
The report turns the error into a next step: retry, repair something by hand, or stop because this file type is not supported.
Repaired downloads are checked again
A repaired EPUB appears only when the change is safe and the fixed file passes EPUBCheck again.
Best fit
Use it when the book is finished but the upload fails.
You are not trying to edit the book. You are trying to find the small EPUB problem that stops the upload.
- KDP rejects the EPUB, but Calibre or another reader still opens it.
- Kindle Previewer mentions a package, metadata, table of contents, link, or missing file problem.
- EPUBCheck returns RSC, OPF, or PKG errors and you want the next step in plain language.
Pick a starting point
Start with what you see on screen.
Use the closest guide, then trace the error back to the file, link, or metadata entry that needs attention.
EPUB opens in Calibre but fails KDP
Start here when the book opens in a reader app, but the upload fails because an internal file path cannot be found.
Kindle Previewer shows EPUB validation errors
Start here when Previewer reports package, metadata, navigation, table of contents, link, or missing-file errors before another KDP upload.
EPUBCheck says unique-identifier was not found
Use this when OPF_030 points to metadata and you need to know whether the book identifier can be fixed safely.
EPUBCheck reports PKG_006 after manual zipping
Use this guide when the book content exists but the EPUB ZIP container has a missing, compressed, or non-first mimetype file.
Common situation
For EPUB files that open on your computer but fail during upload.
Many authors export from Word, Pages, Scrivener, Atticus, Vellum, InDesign, or another formatting tool and only find the problem after KDP or Kindle Previewer rejects the EPUB.
EPUB Fixer looks inside the EPUB package and points to the file, reference, identifier, or navigation entry behind the rejection.
What happens next
Upload, read the report, retry only when it makes sense.
1
Upload
Upload one .epub file exported from Word, Pages, Scrivener, Atticus, Vellum, InDesign, or another formatting tool.
2
Scan
The scanner checks packaging, metadata, the file list, reading order, navigation files, links, image paths, stylesheet paths, and anchors.
3
Review
The report shows the affected path, the likely cause, and whether the issue can be fixed automatically or needs manual work.
4
Download
If a safe automatic fix passes EPUBCheck again, the result page offers a repaired EPUB for another KDP or Kindle Previewer try.
What it checks
Checks the files inside the EPUB, not the look of the book.
- EPUB packaging, including mimetype order, container.xml, and where the OPF file lives
- metadata, file list, reading order, navigation files, and table of contents wiring
- broken links, missing images or stylesheets, missing anchors, and incorrect media types
Reading the report
Each issue says what to do next.
Repairable
The fix is clear, such as correcting a broken file reference or a missing OPF unique identifier. If the repaired EPUB passes another check, a download appears.
Manual fix needed
The problem is found, but the tool cannot safely guess which file, heading, link, or chapter you meant.
Not supported
The file needs conversion, formatting, DRM removal, fixed-layout repair, image-first book repair, or KDP account help.
When a download appears
A repaired download appears only when the file passes the check again.
- the file is a supported EPUB
- the fix does not change the writing, layout, or intended reading order
- the repaired EPUB passes EPUBCheck again
- the upload has not been deleted or expired
What it will not do
It will not convert, redesign, or rewrite the EPUB.
If a fix would require guessing what the book should say, changing prose, choosing a chapter title, redesigning pages, or repairing a fixed-layout picture book, the report stops at diagnosis.
See unsupported casesFAQ
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 fix is safe. The file must be supported, the change must be automatic, and the repaired EPUB must pass EPUBCheck again.
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. The same EPUB problems can also matter for Apple Books, Kobo, Google Play Books, Draft2Digital, and other distributors that reject invalid EPUB files.
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?