Free, no sign-up. We don't store the URLs you preview.
What the card is built from
og:titleandog:description: the text. Without them each platform guesses.og:image: the picture. 1200×630 works everywhere.twitter:cardset tosummary_large_image: the big image on X.
The cards here are close approximations; each platform caches cards, so a change can take a while to show there. For the full list, run the launch readiness checker.