OG image checker

The image is the part of a preview people actually notice, and the part most likely to be wrong in a way nothing tells you about. The tags can declare one size while the file is another; the URL can be unreachable from outside your network; the image can be too small for a platform to use at all.

Size and ratio

1200×630 is the size to use unless you have a reason not to. It is a 1.91:1 ratio, which is what the large-image card layouts are built around, and it is large enough that no platform will reject it as too small.

Declared versus actual

og:image:width and og:image:height let a platform reserve layout space before the image has loaded, so the preview does not reflow. They are useful — and they are also just numbers you typed, with nothing checking them against the file.

When the file is replaced and the tags are not updated, the declared size is now a lie that no browser will ever surface. The checker fetches the image and reads its real dimensions from the file header, then compares.

<meta property="og:image" content="https://acme.com/og.png">
<meta property="og:image:width" content="1200">
<meta property="og:image:height" content="630">
<meta property="og:image:alt" content="Acme pricing table">

Reachable from outside

An image behind a login, on an internal host, or served only to browsers with a session cookie will look perfect to you and fetch as nothing to a crawler.

The checker fetches from outside your network with an ordinary crawler User-Agent, so an image that only works for you shows up as inaccessible rather than as fine.