Paste a URL — see how its card looks on every network and exactly what to fix.
The set of meta tags (og:title, og:image…) that tells X, WhatsApp, LinkedIn and others how to render your link as a card.
Usually a missing og:image, an image that 404s, or a wrong size. This tool tells you exactly which.
They use different fields and image rules — WhatsApp shrinks small images, X needs twitter:card for the large layout, etc. The previews here simulate each.
Networks cache previews. Re-scrape on the network's own debugger (X Card Validator, LinkedIn Post Inspector) or add a cache-busting query.