Paste a link to your site into a chat and look at what comes back. That little card is doing more work than most of your homepage, and on an awful lot of sites it shows a logo, a stretched thumbnail, or nothing at all.
I find this genuinely fascinating, because the share card is the one piece of your design that gets seen by people who have not visited yet. It is a shop window you never look at.
What the platforms actually read
When something scrapes your URL, it looks for a handful of meta tags in the head of the page. The Open Graph set covers most of them, and Twitter cards add a few of their own. The four that matter:
og:title, which is often not your page title.og:description, which is often not your meta description.og:image, the picture.twitter:card, which decides between a small square thumbnail and a big banner.
Most SEO plugins fill these in for you and fall back to something generic when you have not set an image. Generic is where the logo-in-a-gray-box cards come from.
One size covers nearly everything
1200 by 630 pixels. That is the workhorse. It sits at roughly 1.91:1, it is what the large card format expects, and it downsamples gracefully everywhere else.
Two details worth knowing. Some platforms crop toward a square for the small preview, so anything essential should live in the middle two thirds rather than the edges. And several of them will not fetch an image above a certain file size, which is a spectacularly annoying way for a share card to fail, so keep it comfortably compressed.
What belongs on the card
A share card is read in about a third of a second, at thumbnail size, usually on a phone, in a feed full of other things. That is the design brief.
The headline, big. Not your logo. The title is the reason somebody stops. Set it large enough to read at 300 pixels wide, which is much larger than feels right on your monitor.
One visual. A photograph, an illustration, a color field. Not three things fighting.
A small mark of who you are. A logo in a corner at a modest size, or just your site name. It builds recognition across dozens of cards without stealing the space the headline needs.
Contrast that holds. If text sits over a photograph, put a gradient or a scrim underneath it. Always, not only when the photograph happens to be busy, because the next photograph will not be.
What does not belong: your navigation, a paragraph of body text, a call to action, or a URL. There is a real link right next to the card.
The two ways to do it, and the one I use
You can make each card by hand. For a site with twelve pages that is fine and probably better, because you can be clever about each one.
For a blog, it falls apart. Not because it is hard, because it is at the end of the publishing checklist, and things at the end of checklists do not happen at half past eleven on a Friday.
So I generate them. One dynamic template with the title bound to the post title, the category bound to the category, an image slot bound to the featured image, my logo in the corner, and a size range on the headline so a long title shrinks instead of exploding. Then Automation, Images, Featured Images runs it across whatever I select.
That run comes with WunderPaint Pro. The template itself, the bindings and the preview against a real post are free.
With Rank Math or Yoast installed, the same run can set the result as the social image rather than only the featured image, which is the step everybody forgets. The featured image and the OG image are not always the same field, and if you only fill one of them your card falls back to the plugin default.
Two settings that save you later
Skip anything that already has an image. This protects the cards you made deliberately. Without it, one bulk run flattens a year of individual decisions.
Refresh when the title changes. If the headline is baked into the picture, then editing the headline silently makes the card wrong. Regeneration on change keeps the two in step. This is the strongest argument for generating rather than drawing: a hand-made card cannot know that you rewrote the title six months later.
Test it properly, once
Every platform caches aggressively. Share a link, discover the card is wrong, fix it, share again, and you will still see the old one, sometimes for days.
So use the debug and validator tools the platforms publish before you announce anything. They fetch the URL fresh, show you exactly what they parsed, and let you clear the cache for that link. Five minutes with those tools once, at the start, beats discovering the problem on the post you actually cared about.
While you are there, check a page with a very long title, a page with no featured image, and your homepage. Those three cover most of the ways this quietly breaks.
The part that surprised me
I expected this to be a small polish job. What actually happened is that people started sharing posts more, because a link that arrives as a designed card looks like something worth opening, and a link that arrives as a gray rectangle looks like a spam message.
Same article, same words, same site. The only difference is a picture nobody on your own site will ever see.
