What this check inspects
Shipwork reads the Open Graph tags on the page: og:title, og:description, og:image, og:url, og:type and og:site_name, plus twitter:card. It checks that og:image is an absolute URL and that the declared og:image:width and og:image:height meet the 1200 by 630 recommendation for a large preview. When the image is absolute and has declared dimensions, it sends a header-only probe and stops if the file is larger than about two megabytes, then reads only the few header bytes needed to measure a PNG, GIF, WebP or JPEG, and compares the real size against the declared one. The image is never rendered, only measured.
What a failure means
Each missing Open Graph tag is a warning, and a missing og:image gets the strongest wording because it removes the preview image entirely. A relative og:image, missing og:image dimensions, dimensions below 1200 by 630, or a declared size that does not match the real file are warnings. An image larger than the probe limit is reported as informational because its size was not verified. A missing twitter:card is informational, since most platforms fall back to Open Graph.
How to fix it
- Set og:title, og:description, og:image, og:url and og:type on every shareable page rather than relying on the title tag.
- Use an absolute https URL for og:image, and make sure it returns 200 without a login or a bot challenge.
- Declare og:image:width and og:image:height and make them match the real file, at 1200 by 630 or larger.
- Add twitter:card with summary_large_image for a wide preview on X, and keep the image file under the probe limit.
A typical failure, worked through
The setupA theme sets og:image to a relative path and declares 1200 by 630, but the file behind it was re-exported at 600 by 315 during a redesign.
What the check reportsThe check reports that og:image is not absolute, that the dimensions are below the recommendation, and, once the URL is fixed, that the declared size disagrees with the real file.
The pointThe tags in the HTML can all be present and still describe an image that does not match. Only measuring the file catches the mismatch that makes platforms crop or reject the preview.