Mastodon Open Graph Preview

Mastodon expands a wide preview image above the text. Under it, the card shows the provider or hostname, a bold title, and one clipped description line. Images wider than they are tall use the expanded layout; small or square images, or a page with no og:image, get a compact row instead. Mastodon never falls back to twitter:image, and without og:site_name it prints the full hostname, www included.

Use a 1.91:1 image such as 1200×630 and keep essential text away from the edges. Mastodon instances cache preview cards, so an old share may keep the earlier image after you update the page.

Each Mastodon server fetches links for its own users. A page that blocks the instance's bot, requires a login, or returns incomplete metadata can appear as a bare link on one server even when another server already has a cached card.

Set og:title, og:description, og:image, and og:url. Add og:site_name when you want a recognizable provider name above the title. The crawler row above shows whether Mastodon could fetch both the page and its image.