Twitter Card checker

X builds link previews from Twitter Card tags, falling back to Open Graph where a Twitter tag is absent. That fallback is the part people get wrong: a page can look correct on Facebook and wrong on X, or have twitter tags that duplicate the OG ones and change nothing.

Card types

twitter:card decides the shape of the preview. Without it, X may render a small card or none at all, whatever your other tags say.

What falls back, and what does not

X reads twitter:title, twitter:description and twitter:image, and falls back to the Open Graph equivalents when they are missing. So most sites need only two Twitter-specific tags.

twitter:card has no Open Graph equivalent, so it cannot fall back — it is the one tag you genuinely have to write. twitter:site attributes the post to your account and also has no fallback.

This is what the checker's preview means when it tells you a value came from og:description: the tag is doing work, but it is not the tag you might think.

<!-- The two that cannot fall back -->
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:site" content="@acme">

<!-- Only needed if they should differ from the og: values -->
<meta name="twitter:title" content="A headline written for X">
<meta name="twitter:image" content="https://acme.com/x-card.png">

name, not property

Twitter Card tags use name, where Open Graph uses property. Writing property="twitter:card" is a frequent slip and is not part of the specification, though some parsers tolerate it.

The checker reads both attributes and reports the value it found either way, so you can see the tag exists before working out why a platform ignored it.