mozilla/pdf.js · warning · FormatError

Page count is not an integer.

Error message

Page count is not an integer.

What it means

FormatError thrown inside checkHeader / numPages validation when the resolved numPages (from linearization.numPages or catalog.numPages) is not an integer. The surrounding try/catch clears caches and triggers recovery, so end-user impact is usually degraded performance rather than a hard failure. It indicates the page count entry in the linearization dict or catalog Pages /Count is corrupt.

Source

Thrown at src/core/document.js:1772

    let numPages;

    try {
      await Promise.all([
        pdfManager.ensureDoc("xfaFactory"),
        pdfManager.ensureDoc("linearization"),
        pdfManager.ensureCatalog("numPages"),
      ]);

      if (this.xfaFactory) {
        return; // The Page count is always calculated for XFA-documents.
      } else if (this.linearization) {
        numPages = this.linearization.numPages;
      } else {
        numPages = catalog.numPages;
      }

      if (!Number.isInteger(numPages)) {
        throw new FormatError("Page count is not an integer.");
      } else if (numPages <= 1) {
        return;
      }
      await this.getPage(numPages - 1);
    } catch (reason) {
      // Clear out the various caches to ensure that we haven't stored any
      // inconsistent and/or incorrect state, since that could easily break
      // subsequent `this.getPage` calls.
      this.#pagePromises.delete(numPages - 1);
      await this.cleanup();

      if (reason instanceof XRefEntryException && !recoveryMode) {
        throw new XRefParseException();
      }
      warn(`checkLastPage - invalid /Pages tree /Count: ${numPages}.`);

      let pagesTree;
      try {

View on GitHub (pinned to 5903d58d58)

Solutions

1. Repair with qpdf --check / --fix or Acrobat Save As.
2. Re-generate the PDF with a conformant producer.
3. If you observe degraded page-count detection, accept the recovery and log for follow-up.

When it happens

Trigger: A linearization dict whose /N is fractional or missing; a catalog whose /Pages /Count is non-numeric; a corrupt PDF where the Pages tree root has no integer Count.

Common situations: Truncated or hand-edited PDFs; buggy producers that omit /Count; partial downloads.

Related errors

• The Linearization dictionary doesn't point to a valid Page d
• Catalog object is not a dictionary.
• Invalid top-level pages dictionary.
• Page count in top-level pages dictionary is not an integer.
• PageLabel is not a dictionary.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/6b7d1ed032c9209c. Report an issue: GitHub.