No og: image

Hello,

Following is the priority in which Rank Math adds an image in the og:image tag:

1) The Image set in the Social >> Facebook field
2) The featured image
3) The first image from the content.
4) The default image from the Settings.

On your site, Rank Math is not adding the first image from the content because you are using an external image source.

This is a bug in the plugin and I have logged it. Please allow us some time to test and release a fix. It should be added to the plugin in upcoming updates.

For now, to fix the issue on your site, please add following code to your theme’s functions.php file:

add_filter( 'rank_math/opengraph/facebook/image', 'rank_math_set_content_image' );
add_filter( 'rank_math/opengraph/twitter/image', 'rank_math_set_content_image' );
function rank_math_set_content_image( $attachment_url ) {
	if ( $attachment_url || ! is_singular() ) {
		return $attachment_url;
	}

	global $post;
	if ( has_post_thumbnail() || get_post_meta( $post->ID, 'rank_math_facebook_image_id', true ) ) {
		return $attachment_url;
	}

	$content = $post->post_content;
	$images = [];
	if ( preg_match_all( '<code><img [^>]+></code>', $content, $matches ) ) {
		foreach ( $matches[0] as $img ) {
			if ( preg_match( '<code>src=([&quot;\&#039;])(.*?)\1</code>', $img, $match ) ) {
				if ( isset( $match[2] ) ) {
					$images[] = $match[2];
				}
			}
		}
	}

	if ( ! empty( $images ) ) {
		return $images[0];
	}

	return $attachment_url;
}

I hope that helps.