Browser extension
Social Preview Inspector
See the title, description, canonical URL and share image a page really offers to link previews, with warnings.
Paste-and-pray no more: open the page, click, and see exactly what chat apps and social networks will show, plus 14 warning rules for missing or wrong tags. Runs locally, so private and unpublished pages are fine.
Privacy: runs entirely in your browser, on the active tab, only when you click. No account, no network requests, no data collected.
Get it for Firefox Not on the Chrome Web Store yet
The Firefox version is live on addons.mozilla.org. A Chrome Web Store listing is planned but not published; this page will link it when it exists.