mozilla/pdf.js · error · FormatError

Dictionary key must be a name object

Error message

Dictionary key must be a name object

What it means

Thrown as a FormatError by Parser.makeInlineImage() while reading the key-value pairs of an inline image dictionary (the tokens between BI and ID). Inline image keys must be Name objects; if a non-Name token appears where a key is expected, the structure is malformed. Unlike the regular dict parser (which just warns and skips), the inline-image path is stricter and throws.

Source

Thrown at src/core/parser.js:545

      } else if (state === 2) {
        break;
      }
    }
  }

  /**
   * @param {CipherTransform | null} cipherTransform
   * @returns {Streams}
   */
  makeInlineImage(cipherTransform) {
    const lexer = this.lexer;
    const stream = lexer.stream;

    const dict = new Dict(this.xref);
    let dictLength;
    while (!isCmd(this.buf1, "ID") && this.buf1 !== EOF) {
      if (!(this.buf1 instanceof Name)) {
        throw new FormatError("Dictionary key must be a name object");
      }
      const key = this.buf1.name;
      this.shift();
      if (this.buf1 === EOF) {
        break;
      }
      dict.set(key, this.getObj(cipherTransform));
    }
    if (lexer.beginInlineImagePos !== -1) {
      dictLength = stream.pos - lexer.beginInlineImagePos;
    }

    // Extract the name of the first (i.e. the current) image filter.
    const filter = dict.get("F", "Filter");
    let filterName;
    if (filter instanceof Name) {
      filterName = filter.name;
    } else if (Array.isArray(filter)) {

View on GitHub (pinned to 5903d58d58)

Solutions

1. Extract and inspect the page content stream around the BI operator to find the malformed key.
2. Re-export or rebuild the PDF with a reliable producer (Ghostscript, qpdf) to normalize the content stream.
3. If the image is non-essential, catch FormatError during page rendering to still show the rest of the page.

try {
  await page.render({ canvasContext }).promise;
} catch (e) {
  if (e.name === 'FormatError' && /name object/.test(e.message)) { /* malformed inline image */ }
  else throw e;
}

When it happens

Trigger: makeInlineImage() loops while buf1 isn't 'ID' or EOF; each buf1 must be a Name. If a number, string, or Cmd appears as a key, the `instanceof Name` check fails and the FormatError fires. Happens in PDF content streams with malformed inline image syntax.

Common situations: A PDF page content stream with a broken BI/ID inline image — e.g. missing a value so the next token (a value) is read as a key, or an encoder that emitted non-name tokens. Often caused by content-stream corruption or a buggy PDF producer. Less common than the regular-dict variant because inline images are rare.

Related errors

• End of file inside array.
• End of file inside dictionary.
• Duplicate entry in "${this._type}" tree.
• Parent must be a dictionary.
• Kids must be an array.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/fc881c9a2f7922d3. Report an issue: GitHub.