Link Previews turn shared web addresses into rich Markdown cards using metadata the page already publishes.
Metadata
- Open Graph title, description, image, URL, and site name
- Twitter/X Card title, description, image, and URL fallbacks
- Schema.org JSON-LD headline, description, image, publisher, and provider fallbacks
- HTML title, description, and canonical URL fallbacks
- oEmbed JSON discovered from page links or HTTP Link headers
In the Conversation
Paste a link into a channel or a private message and its card appears under the message, with the source, the headline, the byline and reading time, the page's own image, and its summary.
The card is read from the archive when the conversation is drawn, so it survives a reload and is there again when you scroll back. A page nobody has read yet leaves the message untouched until the fetch lands, and then fills in on its own. Turning off text formatting hides cards along with the rest.
Only plain messages get a card, and only for their first link. A message you write in Markdown is left exactly as you wrote it — you have already chosen how the link should look, which is also why a feed bot's own card is never given a second one.
Used By
RSS bots post new feed items as the same card, so a feed item and a link somebody pasted read identically.
Every consumer reads from one shared archive. A page is fetched the first time anyone links to it and kept for 120 days, so the same link posted in another channel, or published later by a feed bot, is answered without contacting the site again.
When a stored page ages out it is refreshed with a conditional request, which most sites answer with "unchanged" — no page is downloaded twice unless it actually changed.
Safety
- Only HTTP and HTTPS URLs are fetched
- URLs with embedded credentials are refused
- Private, local, documentation, benchmark, multicast, and reserved address ranges are blocked
- Redirects and discovered oEmbed/image URLs are checked before use
- Markdown images are sanitized, lazy-loaded, and rendered without referrer leakage
