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.
EPUB error guides
KDP, Kindle Previewer, and EPUBCheck errors explained.
Got a KDP, Kindle Previewer, or EPUBCheck message? Start here before you edit the EPUB. Match the exact code or wording, then see which file path, anchor, metadata field, or ZIP packaging issue usually causes it.
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.
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.
Find the right guide
Start with the exact words on screen.
If KDP, Kindle Previewer, or EPUBCheck shows one of these phrases, open the matching guide first. If the message is still too vague, scan the EPUB to find the affected path.
- RSC_007: Referenced resource could not be found in the EPUB
RSC_007 missing resource
- RSC_012: Fragment identifier is not defined
RSC_012 broken anchor
- OPF file not found in the EPUB
OPF_002 package path
- OPF_030: The unique-identifier was not found
OPF_030 metadata
- PKG_006: Mimetype file entry is missing or is not the first file
PKG_006 ZIP packaging
- Kindle Previewer reports EPUB validation errors
Kindle Previewer report
Common cases
Broken references and anchors
Start here when EPUBCheck or KDP points to a missing image, stylesheet, chapter file, broken link target, or duplicate XHTML id.
- Referenced resource could not be found in the EPUB
How to trace the exact 'referenced resource could not be found' EPUB message back to the broken internal path before another KDP or Kindle Previewer retry.
- RSC_007 referenced resource could not be found
How to read an EPUBCheck RSC_007 error, identify the source file and missing target path, and decide whether the correction is safe before another KDP upload.
- RSC_012 fragment identifier is not defined
How to handle an RSC_012 missing fragment error by checking the file before the # symbol and the anchor id after it before another KDP upload.
- EPUBCheck RSC-005 duplicate ID
What duplicate ID and RSC_005 EPUB parsing errors mean, and why many require careful review.
Common cases
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, or the mimetype file was zipped in the wrong place.
- OPF_030 unique-identifier was not found
How OPF_030 happens when the package unique-identifier points to a missing metadata id, and when that OPF metadata link can be repaired safely.
- OPF_003 item is not declared in the OPF manifest
How to understand the OPF_003 EPUBCheck error when a file exists in the EPUB but is missing from the OPF manifest, and when a manifest repair is safe before KDP upload.
- OPF_048 package is missing unique-identifier
How to understand the OPF_048 package missing unique-identifier error, what to check in EPUB metadata, and when the identifier can be repaired safely.
- OPF_049 item id was not found in the manifest
How to understand the OPF_049 item id was not found in the manifest error when EPUB spine, guide, navigation, or package references point to a missing manifest id.
- OPF file not found in the EPUB
Why OPF_002 happens when container.xml points to a missing package file, and how to scan for a safe fix.
- container.xml missing in EPUB
Why META-INF/container.xml matters, how it points to the OPF package, and when a missing EPUB container file can be rebuilt safely.
- PKG_006 mimetype file entry is missing or not first
How PKG_006 happens when the EPUB ZIP wrapper has a missing, compressed, or misplaced mimetype entry, and when rebuilding the archive is safe.
Common cases
KDP and Kindle Previewer navigation symptoms
Start here when the EPUB opens, but KDP or Kindle Previewer still reports navigation, TOC, or preview validation problems before upload approval.
- KDP EPUB missing table of contents
Why KDP or Kindle Previewer may not show your EPUB table of contents, and what to check before deciding whether the navigation can be fixed safely.
- Kindle Previewer EPUB validation errors
How to read Kindle Previewer EPUB validation errors, map vague messages to EPUB structure problems, and decide whether to scan, repair, or review by hand.
After scanning
The report should leave you with one clear next step.
Either fix it automatically, review the affected file by hand, or stop because the problem is not an EPUB structure issue.
- Automatic fix: the report found one clear package, metadata, reference, or container change.
- Manual check: the affected file is visible, but the right change depends on the book's intended content or reading order.
- Not supported: the issue is conversion, formatting, fixed-layout, DRM, KDP account setup, or another non-EPUB-structure problem.
Not covered
What this page does not cover
- DOCX, PDF, KPF, KCB, or ZIP conversion into EPUB
- fixed-layout, comic, picture book, manga, or image-first EPUB repair
- DRM removal, cover design, typography, book formatting, or KDP account issues