Fill in your page details once, get every Open Graph and Twitter Card tag you need, and see a live preview of how the link will look when shared.
Fill in a page's title, description, URL, and image once and this generates the full set of Open Graph tags (used by Facebook and LinkedIn) plus Twitter Card tags, while rendering a live mock-up of how the link card will actually look when shared. It's meant to save the trial-and-error of pasting tags into a page and re-checking a social platform's debugger every time.
Twitter/X will fall back to your Open Graph tags if Twitter-specific ones are missing, but including explicit `twitter:card` tags is the only way to guarantee the large-image summary layout instead of a smaller, less eye-catching card.
1200×630px (a 1.91:1 ratio) is the commonly recommended size, it displays cleanly as a large image on Facebook, LinkedIn, and Twitter's summary_large_image card without odd cropping on any of them.
Each platform renders its own final layout and may cache an older preview of a URL, so this is a close approximation rather than a pixel-perfect guarantee. After publishing, tools like Facebook's Sharing Debugger or Twitter's Card Validator can force a fresh re-scrape if a stale preview sticks around.