What gets checked
After the page is fetched, the checker reads og:image. It shows the value exactly as published, resolves relative URLs against the final page address, and requests the image from the server. If that request returns an image, the checker says so. Width and height are reported only when they can be read from PNG, GIF, JPEG, WebP, or an SVG with explicit pixel dimensions.
Warnings you may see
- OG image missing. The HTML has no
og:image,og:image:url, orog:image:secure_url. - Image URL is not absolute. The tag is a path such as
/cover.jpg. Browsers can sometimes resolve that on your site. Many crawlers are stricter. Publish a fullhttpsURL. - Image could not be loaded. The URL was public, but the response was an error, a timeout, or not an image.
- Image appears unusually small. At least one side is under 200 pixels. That is a poor fit for a feed card.
A practical size
1200×630 pixels is the size most often used for a large link image. Keep the subject near the center, because crops differ. JPG, PNG, and WebP are the safe formats. If this checker cannot determine a size, it leaves the field blank rather than estimating one.
The rest of the social tags are covered in the Open Graph preview guide.