EPUB Error: Broken Internal Link (RSC-007)

RSC-007 fires when an internal hyperlink inside your EPUB content points to a target that does not exist — either a file that was removed from the package, or an anchor ID that was renamed, deleted, or never created in the target document. The most common cases are footnote links (<a href="#fn-23">) where the corresponding <span id="fn-23"> in the endnotes file was removed during editing, chapter cross-references that became stale after chapters were renumbered or reorganized, and navigation document links that do not match the heading IDs in the chapter files. Because EPUB is XHTML-based, every internal link is validated as a real resolvable reference — unlike HTML in a browser where a broken anchor simply scrolls to the top of the page, EPUB validators treat unresolved internal links as structural errors.

1. Run EPUBCheck and collect all RSC-007 errors — each one includes the file containing the broken link and the exact href value that failed to resolve.
2. For each broken link, determine whether the href targets a fragment identifier only (e.g., #fn-23) or a separate file plus fragment (e.g., endnotes.xhtml#fn-23). If it targets a file, confirm that file exists in the package and is declared in the OPF manifest.
3. Open the target file and search for an element with an id attribute matching the fragment (e.g., id="fn-23"). If absent, either add the missing id to the correct element or update the broken link's href to match an existing id.
4. For footnote and endnote systems, ensure each reference anchor in the chapter body has a matching return link in the notes file, and that both sides use identical id values without typos or case differences.
5. After fixing all instances, re-validate with EPUBCheck and test footnote navigation in Kindle Previewer to confirm links resolve correctly end to end.

Common EPUB errors: Duplicate ID attribute in EPUB, NCX navPoint mismatch, OPF manifest references a missing file