mozilla/pdf.js · error · FormatError

Illegal character: ${ch}

Error message

Illegal character: ${ch}

What it means

Error "Illegal character: ${ch}" thrown in mozilla/pdf.js.

Source

Thrown at src/core/parser.js:1354

        ch = this.nextChar();
        if (ch === 0x3e) {
          this.nextChar();
          return Cmd.get(">>");
        }
        return Cmd.get(">");
      case 0x7b: // '{'
        this.nextChar();
        return Cmd.get("{");
      case 0x7d: // '}'
        this.nextChar();
        return Cmd.get("}");
      case 0x29: // ')'
        // Consume the current character in order to avoid permanently hanging
        // the worker thread if `Lexer.getObj` is called from within a loop
        // containing try-catch statements, since we would otherwise attempt
        // to parse the *same* character over and over (fixes issue8061.pdf).
        this.nextChar();
        throw new FormatError(`Illegal character: ${ch}`);
    }

    // Start reading a command.
    let str = String.fromCharCode(ch);
    // A valid command cannot start with a non-visible ASCII character,
    // and the next character may be (the start of) a valid command.
    if (ch < 0x20 || ch > 0x7f) {
      const nextCh = this.peekChar();
      if (nextCh >= 0x20 && nextCh <= 0x7f) {
        this.nextChar();
        return Cmd.get(str);
      }
    }
    const knownCommands = this.knownCommands;
    let knownCommandFound = knownCommands?.[str] !== undefined;
    while ((ch = this.nextChar()) >= 0 && !specialChars[ch]) {
      // Stop if a known command is found and next character does not make
      // the string a command.

View on GitHub (pinned to 5903d58d58)

Solutions

1. Remove the illegal character from the token being parsed; PDF lexical rules only allow regular characters outside delimiters and whitespace.
2. If the file is corrupted or truncated, obtain a clean copy of the PDF.

When it happens

Trigger: Thrown at src/core/parser.js:1354 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/a96c77fa411172e0. Report an issue: GitHub.