Before you share a link, test how it renders. This free validator inspects your social-preview tags across platforms and flags the exact problems — including the one most tools miss: an og:image that doesn't load.
X uses twitter:card; Facebook/LinkedIn/Slack use Open Graph. If Twitter tags are absent, X falls back to OG — but a summary card, not a large image. Set twitter:card = summary_large_image for the big preview.
Previews break silently when an image is moved or a CDN changes. Add the check to CI (or Pro monitoring) so you find out immediately, not weeks later when traffic drops.