mozilla/pdf.js · error · FormatError

Max size of CID is 65,535

Error message

Max size of CID is 65,535

What it means

Thrown while building the ToUnicode map for a CID font when iterating the font's CMap and encountering a character identifier (CID) greater than 0xFFFF (65,535). CID values are 16-bit by definition; a larger value indicates a corrupt CMap or a CIDSystemInfo/registry mismatch. The check guards against array-index overflow in the toUnicode lookup table.

Source

Thrown at src/core/evaluator.js:3988

      // by the font’s CMap (for example, Adobe and Japan1) from its
      // CIDSystemInfo dictionary.
      const { registry, ordering } = properties.cidSystemInfo;
      // c) Construct a second CMap name by concatenating the registry and
      // ordering obtained in step (b) in the format registry–ordering–UCS2
      // (for example, Adobe–Japan1–UCS2).
      const ucs2CMapName = Name.get(`${registry}-${ordering}-UCS2`);
      // d) Obtain the CMap with the name constructed in step (c) (available
      // from the ASN Web site; see the Bibliography).
      const ucs2CMap = await CMapFactory.create({
        encoding: ucs2CMapName,
        fetchBuiltInCMap: this._fetchBuiltInCMapBound,
        useCMap: null,
      });
      const toUnicode = [],
        buf = [];
      properties.cMap.forEach(function (charcode, cid) {
        if (cid > 0xffff) {
          throw new FormatError("Max size of CID is 65,535");
        }
        // e) Map the CID obtained in step (a) according to the CMap
        // obtained in step (d), producing a Unicode value.
        const ucs2 = ucs2CMap.lookup(cid);
        if (ucs2) {
          buf.length = 0;
          // Support multi-byte entries (fixes issue16176.pdf).
          for (let i = 0, ii = ucs2.length; i < ii; i += 2) {
            buf.push((ucs2.charCodeAt(i) << 8) + ucs2.charCodeAt(i + 1));
          }
          toUnicode[charcode] = String.fromCharCode(...buf);
        }
      });
      return new ToUnicodeMap(toUnicode);
    }

    // The viewer's choice, just use an identity map.
    return new IdentityToUnicodeMap(properties.firstChar, properties.lastChar);

View on GitHub (pinned to 5903d58d58)

Solutions

1. Repair or regenerate the CMap data in the offending font; ensure CID values fit in 16 bits.
2. Re-export the PDF through Ghostscript (gs -sDEVICE=pdfwrite) which normalizes CID/CMap structures.
3. Catch the error per-page and continue rendering with an incomplete ToUnicode map (search/copy fidelity will suffer).
4. If authoring CJK content with a custom tool, validate CID ranges against the relevant Adobe CMap resource before embedding.

Example fix

// before
await page.getTextContent(); // throws if a CID > 0xFFFF

// after
try {
  await page.getTextContent();
} catch (e) {
  if (/Max size of CID/.test(e.message)) {
    console.warn('CID font corrupt, text extraction will be partial');
  } else throw e;
}

try {
  await page.getTextContent();
} catch (e) {
  if (e.name === 'FormatError' && /Max size of CID/.test(e.message)) {
    // CID font corrupt; accept partial text extraction
  } else throw e;
}

When it happens

Trigger: A composite (Type0/CID) font whose CMap yields a CID > 65535 during the registry-ordering-UCS2 mapping step. Fires in buildToUnicode() inside PartialEvaluator, only for fonts whose CIDSystemInfo is one of the standard Adobe collections (GB1, CNS1, Japan1, Korea1).

Common situations: Corrupt or hand-built CMap data, a CID font whose CMap was concatenated with a wrong/use CMap, or a generator that emitted non-truncated CID ranges. Rare in the wild but seen in PDFs produced by experimental or academic CJK typesetting tools.

Related errors

• Unknown CMap name: ${name}
• Built-in CMap parameters are not provided.
• Unsupported CID string (charCode ${charCode}): "${cid}".
• Max size of CID is 65,535
• mapCidRange - ignoring data above MAX_MAP_RANGE.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/fb170e84d5b13d23. Report an issue: GitHub.