social.og-image-missingNo share image
Why it matters
The image is most of a link preview: on Facebook, LinkedIn, WhatsApp, Slack and Discord a shared link without og:image is a line of grey text that people scroll past, where one with an image is a card that fills the width of the feed. It is one of the four properties the Open Graph protocol requires, and LinkedIn lists it as required for a preview. Some networks guess an image from the page instead, and the guess is usually a logo fragment or an advert.
Sources: The Open Graph protocol; Facebook: images in link shares; LinkedIn: make your website shareable.
How to fix it
Make an image of 1200×630 pixels (JPEG or PNG, under 600 KB) with the page's subject or your brand on it, upload it, and add inside <head>, with the full address:
<meta property="og:image" content="https://www.example.com/share.png" />
<meta property="og:image:width" content="1200" />
<meta property="og:image:height" content="630" />
<meta property="og:image:alt" content="A three-tier wedding cake with fresh flowers" />One good image for the whole site is far better than none; a different one per page is better still.