Referenced resource could not be found
Find broken image, CSS, XHTML, nav, NCX, or OPF references that can make KDP reject a file even when it opens locally.
KDP upload error scanner
EPUB Fixer for KDP upload errors.
Upload a reflowable EPUB 2/3 file, get a plain-English error report, and download a repaired EPUB beta when a safe fix passes revalidation.
Reflowable EPUB 2/3EPUBCheck revalidationNo content rewriting
Best for files that open locally but fail KDP, Kindle Previewer, or EPUBCheck.
Common KDP blockers
Start with the error message you actually see.
The fastest path is matching the exact KDP wording to the structural issue behind it.
RSC-012 fragment identifier error
Check links that point to anchors, notes, headings, or TOC targets that no longer exist inside the EPUB.
OPF unique identifier not found
See whether the package unique-identifier can be aligned with a clear dc:identifier entry.
Mimetype file missing or not first
Diagnose EPUB ZIP packaging problems caused by manual zipping or archive tools.
Standards context
The scan follows EPUB structure rules, not formatting taste.
These references explain why the product focuses on package files, manifests, navigation, internal references, and revalidation instead of editing manuscript content.
EPUB 3.3 package structure
EPUB publications rely on package metadata, manifest entries, spine order, navigation documents, and the OCF container. EPUB Fixer checks these structure points instead of editing book design.
EPUBCheck conformance checking
EPUBCheck evaluates EPUB 2 and EPUB 3 files against official EPUB specifications. EPUB Fixer uses the same validation mindset to separate deterministic repairs from manual judgment.
KDP EPUB upload expectations
KDP supports EPUB uploads that meet Kindle Publishing Guidelines and recommends checking the file in Kindle Previewer before upload. EPUB Fixer is for EPUB structure errors in that pre-upload loop.
Use case
Use it when a finished EPUB is blocked by validation.
The useful question is not “is this a good book file?” It is “which structure error is blocking upload, and is the fix deterministic?”
- KDP says an EPUB upload has a validation error, but the file still opens in a local reader.
- Kindle Previewer points to a package, metadata, TOC, link, or missing resource problem.
- EPUBCheck returns RSC, OPF, or PKG errors and you need to know whether a targeted repair is safe.
When it helps
For EPUB files that open locally but fail upload checks.
Many authors export from Word, Pages, Scrivener, Atticus, Vellum, InDesign, or a formatting tool and only see the problem after KDP or Kindle Previewer rejects the file.
EPUB Fixer focuses on the package structure behind those errors, so you can see which file, reference, identifier, or navigation entry is causing the rejection.
How the scan works
A short path from failed upload to a usable diagnosis.
1
Upload
Send one reflowable .epub file exported from Word, Pages, Scrivener, Atticus, Vellum, InDesign, or another formatting tool.
2
Scan
The scanner checks EPUB container rules, OPF metadata, manifest entries, spine, nav, NCX, internal links, media paths, and anchors.
3
Review
The report explains the affected file path, likely cause, and whether the issue is repairable, manual, or out of scope.
4
Download
When a deterministic repair passes internal EPUBCheck revalidation, the result page offers a repaired EPUB beta for a KDP or Kindle Previewer retry.
Scan scope
Checks EPUB structure, not book design.
- mimetype order, container.xml, and OPF package location
- OPF identifiers, metadata, manifest, spine, nav, and NCX wiring
- broken internal links, missing resources, fragment IDs, and media types
Report output
Every issue is grouped by the next action.
Repairable
The target change is deterministic, such as a broken manifest reference or missing OPF unique identifier. If the repaired EPUB passes revalidation, a beta download appears on the result page.
Manual fix needed
The file can be located, but fixing it safely would require choosing between multiple possible author-intended targets.
Out of scope
The upload looks like fixed-layout, DRM, image-first, conversion, formatting, or KDP account work.
Repaired EPUB download
Download appears only after a safe repair passes revalidation.
- the EPUB is reflowable and accepted by the preflight checks
- the issue is a deterministic structure repair, not a formatting or content decision
- the repaired EPUB passes the internal EPUBCheck revalidation step
- the upload has not been deleted or expired
Hard boundary
No conversion, formatting, or content rewriting.
If a fix would require guessing the author intent, changing prose, choosing a chapter title, redesigning pages, or repairing a fixed-layout picture book, the report stops at diagnosis.
See unsupported casesFAQ
Quick answers before you upload.
Can EPUB Fixer repair every KDP upload error?
No. It focuses on deterministic EPUB structure problems. If a repair would require guessing chapter order, rewriting content, choosing a heading, or redesigning layout, the report stops at diagnosis.
When can I download a repaired EPUB?
A repaired EPUB beta is available only when the upload passes scope checks, the repair is deterministic, and the repaired file passes internal EPUBCheck revalidation.
Is this a DOCX to EPUB converter?
No. Upload an existing reflowable EPUB 2 or EPUB 3 file. DOCX, PDF, KPF, KCB, ZIP archives, fixed-layout books, comics, and image-first books are outside the V1A scope.
Why does an EPUB open locally but fail KDP?
Reading apps can be forgiving. KDP and EPUBCheck validate package structure, manifest declarations, navigation files, anchors, media paths, and ZIP packaging more strictly.
Does the scan change my manuscript?
The scanner does not rewrite prose, design, or author intent. It may generate a repaired EPUB beta only for safe package, OPF, manifest, spine, nav, NCX, or mimetype structure fixes.
Ready to retry?