Which tags does a link preview need?
Three do most of the work, and a fourth covers X.
- og:title: the headline of the card.
- og:description: one or two lines under it.
- og:image: the picture, ideally 1200 by 630 pixels.
- twitter:card set to summary_large_image, so X shows the large picture.
What makes a good preview image?
Use a picture made for the purpose, with your name and a short line of text large enough to read on a phone. Keep the important part away from the edges, since some apps crop to a square. A logo on a plain background is better than a random photo from the page.
Why does the old preview still show after I change it?
Apps keep a copy of the preview for days or weeks. Facebook and LinkedIn each offer a free debugger page where you can paste the link and ask for a fresh copy. In chat apps, the old preview usually clears on its own.
Does this affect search rankings?
Not directly. It affects how many people click when your link is shared, and shared links that get clicked bring visitors and, over time, links from other sites.