Scan first
You only have the duplicate id value.
Find every occurrence and every href, nav, toc, footnote, or backlink that points to the same id.
EPUB error guide
EPUBCheck RSC-005 duplicate ID
What duplicate ID and RSC_005 EPUB parsing errors mean, and why many require careful review.
1. Example report output
What the RSC_005 report should show.
A useful duplicate id report should show the repeated value and whether links make automatic repair risky.
EPUBCheck message
ERROR(RSC-005): OEBPS/Text/chapter2.xhtml(88,12): Error while parsing file: duplicate ID "note-4".
KDP / Previewer wording
The EPUB contains invalid XHTML or a duplicate anchor that prevents reliable conversion.
EPUB Fixer report
chapter2.xhtml has two id="note-4" values. nav.xhtml and footnote backlinks may target one of them.
Do this next
Rename and update links only when the intended target for each duplicate is clear.
Do not do this
Do not delete one id before checking TOC links, footnotes, endnotes, backlinks, and internal anchors.
Safe repair is possible only when the duplicate can be separated without changing where readers land.
2. Next step
Choose the next step from the duplicate id context.
RSC_005 can be a small XHTML cleanup or a navigation-risk problem.
Safe repair
One duplicate is clearly accidental.
Rename the accidental duplicate and update affected links only when the intended targets remain clear.
Manual review
The duplicate affects notes or navigation.
Stop when footnotes, endnotes, repeated headings, MathML, semantic markup, or reading order are involved.
3. Concrete path example
A typical RSC_005 duplicate id problem.
The report should connect the repeated id to the links that might break.
EPUBCheck: ERROR(RSC-005): OEBPS/Text/chapter2.xhtml(88,12): Error while parsing file: duplicate ID "note-4". Report: File: OEBPS/Text/chapter2.xhtml Duplicate id: note-4 References: chapter2.xhtml#note-4, nav.xhtml#note-4 Fix decision: manual review if footnote backlinks use the same id After: validate XHTML and EPUBCheck again
If both copies are footnote targets or reader navigation anchors, passing EPUBCheck is not enough; the links still need to land in the right place.
Quick decision
Decide whether RSC_005 is a simple duplicate or a link-risk issue.
The more links that point to the id, the less safe an automatic rename becomes.
Scan first
Find every occurrence and reference.
Use the file path and id value from EPUBCheck, then search nav, toc, XHTML links, footnotes, and backlinks.
Safe fix
One duplicate is unused and accidental.
Rename or remove only the accidental duplicate, update any affected links, and validate the EPUB again.
Stop
The duplicate controls navigation or notes.
Do not auto-rewrite footnotes, endnotes, semantic markup, repeated headings, MathML, or reading-order anchors.
Start here
Start with the XHTML file and duplicate id.
RSC_005 can look like a simple rename, but duplicate ids are often tied to TOC anchors, footnotes, backlinks, or repeated headings. Find every reference before changing one.
What it means
IDs are supposed to be unique within a document. Duplicate IDs can break links, footnotes, TOC anchors, and reading system behavior.
Can it be fixed automatically?
EPUB Fixer can help with simple duplicate attributes or clearly isolated duplicate IDs when the affected links can be updated and the file passes EPUBCheck again.
What to check next
Find the XHTML file named in the validator message before editing any other file.
What not to assume
Do not rewrite complex XHTML structure, MathML-heavy content, semantic footnotes, or cases where changing an id would break intended reading links.
Common situations
Common RSC_005 duplicate id cases.
Duplicate ids often appear after editing or conversion, but the safe action depends on what points to the id.
Two headings use the same generated id.
A converter created id="chapter-title" more than once in the same XHTML file.
Rename only if TOC and internal links can be updated cleanly.
Footnotes were copied between chapters.
The same note id appears twice and backlinks may return to different paragraphs.
Manual review is safer unless every footnote link target is obvious.
A section was duplicated during editing.
Copy-paste preserved old anchors inside a repeated block.
Check whether the duplicate block is intended content before editing ids.
Malformed XHTML is reported near a duplicate id.
The parser may stop at the id while the real issue is broken surrounding markup.
Inspect the local XHTML before making id-only changes.
The RSC_005 duplicate id error text
RSC_005: Error while parsing file. Duplicate ID.
Where RSC_005 appears in EPUBCheck and Kindle checks
EPUBCheck cannot parse an XHTML file cleanly because the same id appears more than once, or markup is malformed.
What it means
RSC_005 usually starts inside one XHTML file.
IDs are supposed to be unique within a document. Duplicate IDs can break links, footnotes, TOC anchors, and reading system behavior.
Duplicate IDs often appear after copy-paste editing, automatic export bugs, or manual XHTML edits.
Before you edit
Trace the duplicate id and every link that targets it.
The safe question is not just whether the id is repeated. It is whether renaming one copy can preserve the intended reading target and all backlinks.
- 1Find the XHTML file named in the validator message before editing any other file.
- 2Search that XHTML file for the duplicate id value or malformed markup reported by EPUBCheck.
- 3Check whether nav.xhtml, toc.ncx, footnotes, endnotes, or internal links point to that id.
- 4Rename or remove a duplicate only when you can update every affected link without changing the reading target.
- 5Avoid automatic changes when the duplicate id affects footnotes, semantic markup, repeated headings, or reading order.
Why KDP checks it
Why duplicate ids break EPUB validation.
EPUBCheck
EPUBCheck checks EPUB 2 and EPUB 3 files against the official rules and reports package, markup, link, and file-reference problems.
EPUB 3.3 package rules
The OPF file is the EPUB's map: metadata, file list, reading order, and navigation wiring. KDP and EPUBCheck use it to decide whether the book package is coherent.
Can this be fixed safely?
When a duplicate id repair is safe.
When automatic repair is safe
EPUB Fixer can help with simple duplicate attributes or clearly isolated duplicate IDs when the affected links can be updated and the file passes EPUBCheck again.
When you need manual review
Do not rewrite complex XHTML structure, MathML-heavy content, semantic footnotes, or cases where changing an id would break intended reading links.
Before / after example
Before: two headings use id="subhead-1". After: a safe repair is only possible if references can be updated without changing reading order or meaning.
Ready to retry?
Scan duplicate ids before editing XHTML.
A scan should show the file path, line number, repeated id value, and any TOC, nav, footnote, endnote, or internal link that points to that id.
Upload EPUB to scanFAQ
Questions authors ask about EPUBCheck RSC-005 duplicate ID.
What does EPUBCheck RSC-005 duplicate ID mean?
It means an XHTML document contains repeated id values or malformed markup that prevents EPUBCheck from parsing the file safely. Duplicate ids can break TOC links, footnotes, and internal anchors.
Can EPUB Fixer repair duplicate ID errors automatically?
Only in simple cases where one duplicate can be renamed and all affected links can be updated safely. If the duplicate affects footnotes, semantic markup, or reading order, the report should stop for manual review.
Why can a duplicate ID pass a local reader but fail validation?
Some readers ignore repeated ids or choose the first match. KDP, Kindle Previewer, and EPUBCheck need valid XHTML structure so links and navigation targets resolve consistently.
Should I just delete one duplicate id?
Only if no link, TOC entry, footnote, or backlink depends on it. Deleting the wrong id can pass validation while breaking reader navigation.