mozilla/pdf.js · error · Error

Invalid thumbnails rotation angle.

Error message

Invalid thumbnails rotation angle.

What it means

Thrown by PDFThumbnailViewer.pagesRotation setter when the rotation value fails isValidRotation (must be an integer multiple of 90: 0, 90, 180, 270, ...). Thumbnails mirror the page rotation and require a valid angle.

Source

Thrown at web/pdf_thumbnail_viewer.js:487

          shouldScroll = percent < 100;
          break;
        }
      }
      if (shouldScroll) {
        thumbnailView.div.scrollIntoView(SCROLL_OPTIONS);
      }
    }

    this._currentPageNumber = pageNumber;
  }

  get pagesRotation() {
    return this._pagesRotation;
  }

  set pagesRotation(rotation) {
    if (!isValidRotation(rotation)) {
      throw new Error("Invalid thumbnails rotation angle.");
    }
    if (!this.pdfDocument) {
      return;
    }
    if (this._pagesRotation === rotation) {
      return; // The rotation didn't change.
    }
    this._pagesRotation = rotation;

    const updateArgs = { rotation };
    for (const thumbnail of this._thumbnails) {
      thumbnail.update(updateArgs);
    }
  }

  cleanup() {
    for (const thumbnail of this._thumbnails) {
      if (thumbnail.renderingState !== RenderingStates.FINISHED) {

View on GitHub (pinned to 5903d58d58)

Solutions

1. Pass only integer multiples of 90 (0, 90, 180, 270).
2. Normalize input before setting: rotation = Math.round(rotation / 90) * 90 % 360.
3. Guard with isValidRotation from ui_utils before assigning.

Example fix

// before
thumbnailViewer.pagesRotation = rawDegrees;

// after
function normalizeRotation(r) {
  if (!Number.isInteger(r) || r % 90 !== 0) return null;
  return ((r % 360) + 360) % 360;
}
const rot = normalizeRotation(rawDegrees);
if (rot !== null) thumbnailViewer.pagesRotation = rot;

function validRotation(r) {
  return Number.isInteger(r) && r % 90 === 0;
}
if (validRotation(degrees)) {
  thumbnailViewer.pagesRotation = degrees;
}

function isValidRotation(angle) {
  return Number.isInteger(angle) && angle % 90 === 0;
}

When it happens

Trigger: Setting pdfThumbnailViewer.pagesRotation = 45, or a non-integer/NaN/non-number value. Also from passing rotation derived from user input or a corrupted state without normalization.

Common situations: Custom toolbar rotation controls passing arbitrary degrees; deserialization of saved rotation state; passing a float like 90.0 is fine, but 45.5 or NaN throws.

Related errors

• Not enough parameters.
• The overlay does not exist.
• Invalid pages rotation angle.
• BinaryCMapReader.process: Invalid dataSize.
• Page count in top-level pages dictionary is not an integer.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/1e0a856858af056e. Report an issue: GitHub.