Short answer
Images fail when they aren't PNG or JPG, aren't square, are larger than 1200 × 1200 pixels, or aren't publicly accessible. Image URLs must return the image itself, not a preview or sign-in page.
Quick fixes
- Export as PNG or JPG at 1200 × 1200 or smaller, square
- Host on your domain or CDN, AWS S3/CloudFront, or a public Google Drive link
- Test the URL in a private browser window: it should show only the image
- Make sure your CDN doesn't block crawlers
Questions
Can I use WebP?
Not according to the specs: use PNG or JPG.
Facts checked against the sources below on 12 October 2026. Platforms change quickly: if something here no longer matches what you see, tell us and we will update it.
