Why the preview is worth more than the traffic
When a link is shared on WhatsApp, LinkedIn or X, the preview card is the entire advertisement. A card with a clear image and a real headline is a link people tap; a bare blue URL with no image is a link people scroll past, whatever is behind it.
In India this weighs more heavily than the global averages suggest, because so much sharing happens in WhatsApp groups rather than on public feeds. A link forwarded into a group of forty people either carries a card or does not, and that single difference decides whether anyone opens it.
It costs about six lines of HTML, set once per page, usually by a template. It is one of the few genuinely high-return, low-effort things left in this area.
The mistake that breaks most cards
A relative og:image. Writing content="/images/og.png" works everywhere else in HTML, because your browser resolves it against the current page — and fails here, because Facebook, LinkedIn and WhatsApp fetch the image from their own servers, where that path resolves to nothing.
The result is a card with no image and no error message, which is why it survives so long: nothing tells you, and the person who shared the link is not the person who wrote the tag. Every image URL must be absolute, starting with https://.
Two more that follow closely: an image served over http, which some platforms refuse to load into an HTTPS context, and og:url pointing at a tracking-parameter version of the page, which fragments the share count across every campaign that ever linked to it.
Sizing, caching and testing
1200×630 is the size to use. It is the standard large-format ratio, and it degrades acceptably everywhere else — including WhatsApp's small square thumbnail, which centre-crops. Keep essential text away from the edges, because different platforms crop differently.
Every platform caches aggressively. Change your tags and the old preview keeps appearing for days, which is exactly when people conclude the tags do not work and start rewriting things that were already correct.
Force a refresh instead: Facebook's Sharing Debugger, LinkedIn's Post Inspector and X's card validator each re-fetch on demand. WhatsApp uses Facebook's cache, so the Sharing Debugger covers it too. Run those once after publishing and the problem disappears.