Link previews
The card under a pasted link, where it comes from, and what the other site learns.
Paste a link into a post and a card appears under it with the page's title, description and picture.
Who fetches it Copy a link to this section
Our server, not your browser, and not the browser of anybody reading the post.
That distinction is the whole design. If your browser fetched the page, the site at the other end would learn that you were about to link to it. If every reader's browser fetched it, that site would learn about every person who read your post.
Instead the server fetches the page once, some time after you write it, and keeps its own copy of the picture. Reading the post afterwards contacts nobody.
What the other site learns Copy a link to this section
That something at Easybie asked for the page. No cookies are sent, no referrer, and nothing about you — not your address, not your account, not the post.
They cannot tell who wrote the link or who read it.
Why it sometimes takes a moment Copy a link to this section
The fetch happens in the background rather than while you wait, so publishing is not held up by somebody else's slow server. The card usually appears within a minute of the post going out.
If it never appears, the page probably refused the request or has nothing to describe itself with. The link still works; it is just a link.
When there is no card Copy a link to this section
Some sites give nothing to describe themselves with, and some refuse automated requests entirely. Neither is a fault at this end.
A moderator can also turn previews off across the whole site during a busy spell — they are the heaviest thing the background queue does. Existing cards stay; new ones wait.