The Browser Doesn't Decide What Gets Shown — the Page Does
When a link gets pasted into Facebook, LinkedIn, Slack, or X, the platform doesn't screenshot the page — it sends a request to fetch the page's HTML and looks for a specific set of meta tags in the <head> to build the preview card: a title, a description, and an image, plus a few platform-specific variations. If those tags are missing, incomplete, or point to a broken image URL, the resulting preview is whatever the platform falls back to — often no image, a generic site description, or no card at all.
Open Graph: the De Facto Standard
Open Graph tags (prefixed og:) were originally a Facebook-specific format but are now read by the overwhelming majority of platforms that generate link previews, including LinkedIn, Slack, Discord, and many others — making them the single most important set of tags for controlling how a shared link looks almost everywhere. The core four are og:title, og:description, og:image, and og:url; missing any one of them is the most common reason a shared link's preview looks incomplete.
Why X (Twitter) Needs Its Own Tags
X reads its own twitter:-prefixed tags in preference to Open Graph tags when both are present, which is why a page can look perfect when shared on LinkedIn but broken or generic on X if only Open Graph tags were added. The twitter:card tag also controls layout — summary shows a small thumbnail next to the text, while summary_large_image shows a full-width image above it; using the large-image variant without actually having set an image tag can result in an odd-looking card with a broken image slot.
Why the Title Tag Alone Isn't Enough
The standard <title> tag controls the browser tab and search result headline, but most social platforms specifically look for og:title first and only fall back to the plain title tag if it's missing. A page can have a perfectly good title tag for SEO and still show an unrelated or truncated title when shared, if og:title was never set — the two tags serve overlapping but distinct purposes, and skipping one doesn't automatically get covered by the other.
Testing Before It Matters
The failure mode for missing or broken meta tags is almost always discovered after sharing, not before — the link goes out, looks wrong, and by then it's already been seen. Generating and reviewing every relevant tag before publishing, with an accurate preview of what the card will actually look like, catches the truncation, missing image, and inconsistent-title problems while they're still a two-minute fix instead of a public correction.