mozilla/pdf.js · error · FormatError

Page dictionary kids object is not an array.

Error message

Page dictionary kids object is not an array.

What it means

Thrown in Catalog.getPageDict() (catalog.js:1423) when a /Pages dictionary's /Kids entry is not an array, after the inline-Page recovery path (handling producers that inline Page dicts directly in Kids) also fails. /Kids must be an array of references; a non-array with a present /Kids that is not /Page-typed is invalid.

Source

Thrown at src/core/catalog.js:1423

        kids = await xref.fetchAsync(kids);
      }
      if (!Array.isArray(kids)) {
        // Prevent errors in corrupt PDF documents that violate the
        // specification by *inlining* Page dicts directly in the Kids
        // array, rather than using indirect objects (fixes issue9540.pdf).
        let type = currentNode.getRaw("Type");
        if (type instanceof Ref) {
          type = await xref.fetchAsync(type);
        }
        if (isName(type, "Page") || !currentNode.has("Kids")) {
          if (currentPageIndex === pageIndex) {
            return [currentNode, null];
          }
          currentPageIndex++;
          continue;
        }

        throw new FormatError("Page dictionary kids object is not an array.");
      }

      // Always check all `Kids` nodes, to avoid getting stuck in an empty
      // node further down in the tree (see issue5644.pdf, issue8088.pdf),
      // and to ensure that we actually find the correct `Page` dict.
      for (let last = kids.length - 1; last >= 0; last--) {
        const lastKid = kids[last];
        nodesToVisit.push(lastKid);

        // Launch all requests in parallel so we don't wait for each one in turn
        // when looking for a page near the end, if all the pages are top level.
        if (
          currentNode === this.toplevelPagesDict &&
          lastKid instanceof Ref &&
          !pageDictCache.has(lastKid)
        ) {
          pageDictCache.put(lastKid, xref.fetchAsync(lastKid));
        }

View on GitHub (pinned to 5903d58d58)

Solutions

1. Repair with 'mutool clean' or 'qpdf --linearize' to normalise /Kids into an array of refs.
2. Run 'qpdf --check' to detect the malformed /Kids before runtime.
3. Enable recovery/ignoreErrors so PDF.js can skip the broken subtree.
4. If producing PDFs, always emit /Kids as a PDF array of indirect references.

// Cannot cheaply validate /Kids shape pre-load via public API.
// Repair: qpdf --linearize in.pdf out.pdf

try {
  const page = await pdf.getPage(n);
} catch (err) {
  if (/kids object is not an array/i.test(err?.message)) {
    console.warn('/Kids is not an array; document needs repair', err);
  } else throw err;
}

When it happens

Trigger: currentNode.getRaw('Kids') (after ref-fetch) is not an Array, and the node is not a /Page (isName(type,'Page') false) and still has a Kids key, so the recovery branch at line 1415 does not apply. Reached during getPage(n).

Common situations: A producer that wrote /Kids as a single dict or scalar instead of an array; a corrupt page tree where /Kids was overwritten; an edited PDF. Known-corrupt specimens are partially tolerated (issue9540.pdf) before this throws.

Related errors

• Pages tree contains circular reference.
• Page dictionary kid reference points to wrong type of object
• Page index ${pageIndex} not found.
• The reference does not point to a /Page dictionary.
• Node must be a dictionary.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/5240f085aff9771f. Report an issue: GitHub.