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image.not-an-image

Image URL does not serve an image. Level: Warning.

When it is raised

Raised when the API's crawler receives a 2xx response for the image but the Content-Type header does not begin with image/ (compared case-insensitively). The message names the content type served, or says "another content type" when the header is absent.

What it does to a shared link

The response is not treated as an image, so no dimensions, size or crop are measured and the image checks that depend on a loaded image do not run. The robots.txt checks for the image host still run, because that file is fetched separately.

How to fix it

  1. Open the image URL and confirm it serves the image file itself rather than an HTML page such as a login page or a not-found page with status 200.
  2. Configure the server or storage bucket to send the response header Content-Type: image/png or Content-Type: image/jpeg for the file.
  3. If the tag points at a page, change it to the direct URL of the image file.
<meta property="og:image" content="https://example.com/card.png">

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