mozilla/pdf.js · error · Error

Encoding required.

Error message

Encoding required.

What it means

Thrown by CMapFactory.create when the encoding argument is neither a Name nor a BaseStream - the only two supported input shapes. It means the caller passed undefined, a raw string, a number, or a malformed dictionary entry where a CMap/encoding was expected.

Source

Thrown at src/core/cmap.js:720

      if (encoding.isAsync) {
        const bytes = await encoding.asyncGetBytes();
        if (bytes) {
          encoding = new Stream(bytes, 0, bytes.length, encoding.dict);
        }
      }
      const parsedCMap = await parseCMap(
        /* cMap = */ new CMap(),
        /* lexer = */ new Lexer(encoding),
        fetchBuiltInCMap,
        useCMap
      );

      if (parsedCMap.isIdentityCMap) {
        return createBuiltInCMap(parsedCMap.name, fetchBuiltInCMap);
      }
      return parsedCMap;
    }
    throw new Error("Encoding required.");
  }
}

export { CMap, CMapFactory, IdentityCMap };

View on GitHub (pinned to 5903d58d58)

Solutions

1. Repair the PDF so the font dictionary has a valid /Encoding (Name or stream).
2. If calling the API directly, pass a Name (e.g. Name.get('Identity-H')) or a BaseStream wrapping CMap bytes.

Example fix

// before
CMapFactory.create({ encoding: 'Identity-H' }); // raw string

// after
import { Name } from './primitives.js';
CMapFactory.create({ encoding: Name.get('Identity-H') });

import { Name } from './primitives.js';
import { BaseStream } from './base_stream.js';

function validateEncoding(encoding) {
  if (!(encoding instanceof Name) && !(encoding instanceof BaseStream)) {
    throw new TypeError('encoding must be a Name or BaseStream');
  }
}

function isCMapEncoding(encoding) {
  return encoding instanceof Name || encoding instanceof BaseStream;
}

When it happens

Trigger: Calling CMapFactory.create({ encoding: undefined }) or { encoding: 'Identity-H' } (raw string instead of Name), or a PDF whose font /Encoding or ToUnicode reference resolves to something other than a Name or stream.

Common situations: Corrupt PDF with a missing or wrong-typed /Encoding entry; programmatic misuse of the internal CMapFactory API by a downstream library.

Related errors

• mapCidRange - ignoring data above MAX_MAP_RANGE.
• mapBfRange - ignoring data above MAX_MAP_RANGE.
• mapBfRangeToArray - ignoring data above MAX_MAP_RANGE.
• Malformed CMap: expected string.
• Malformed CMap: expected int.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/34c1ba260b860f82. Report an issue: GitHub.