What your link looks like when shared
Paste the head section. The preview shows the card, and tells you which tag produced each part of it.
Paste a head section to see how the link will look when shared.
Which tags control the share preview?
og:title, og:description and og:image do most of the work, and every major platform reads them. twitter:card decides whether X shows the wide image or the small square one. Where og:title is missing, platforms fall back to twitter:title and then to the page title, which is why a page can look fine in search and wrong in a share.
What size should the og:image be?
1200 by 630 is the safe answer: it fits the 1.91:1 ratio every platform crops to. Smaller than 600 wide and some platforms refuse to show it at all, falling back to the small card or no image.
I changed the tags and the old preview is still showing
Platforms cache scraped tags, often for days. Changing the markup does not change an existing share. Each platform has its own debugging tool that forces a re-scrape, and that is the only reliable way to refresh it.
Does a share image affect SEO?
Not directly. It affects how many people click a shared link, which affects how much traffic and how many links the page gets, which does affect SEO. The effect is real but it is second order.
Other tools
This tool checks one page at a time. Visorank does the same work across every page on your site continuously, and shows you which queries people actually search rather than estimates.
What Visorank does