Why a shared link looks the way it does
Paste a link into Slack, WhatsApp, X or Facebook and a card appears with a title, a short blurb and an image — that card is not generated from the visible page content. It is built from a small set of <meta> tags in the page's <head> called Open Graph tags, a convention originally introduced by Facebook and now read by essentially every platform that unfurls links. If those tags are missing, wrong, or point at an image that no longer exists, the preview is blank, generic, or embarrassingly outdated — and it is worth checking rather than assuming it is fine.
The tags that actually matter
| Tag | What it controls |
|---|---|
| og:title | The bold headline shown in the preview card |
| og:description | The one or two lines of body text under the title |
| og:image | The preview thumbnail — the single biggest factor in whether people click |
| og:url | The canonical URL the platform associates the share with |
| og:site_name | The site name shown in small text, often near the URL |
Fill these in and this tool generates the exact HTML block to paste into your page's <head>.
The image size mistake that ruins previews
The single most common reason a preview looks bad is an og:image that is the wrong shape. Platforms expect roughly a 1.91:1 ratio — 1200×630 pixels is the widely used safe size — and a square or portrait image gets awkwardly cropped or centred with ugly padding by whatever algorithm the platform uses to fit it into a fixed frame. Always use an absolute URL for the image, not a relative path; a relative path resolves differently — or not at all — depending on how the crawler fetches your page.
Why the preview does not update when you change the tags
Platforms cache the preview the first time a link is shared, sometimes for a long time, so editing your tags and re-sharing the same URL often shows the old cached card rather than the new one. Most major platforms provide a debugging tool that also forces a cache refresh — Facebook's Sharing Debugger and X's Card Validator are the two most commonly needed. Without using one of those, you may be looking at a stale preview and wrongly concluding your tags did not work.