All links to Twitter tweets, Instagram photos and YouTube videos are beautifully rendered so that you’ll see what the link is all about before opening it. Once you paste a URL to the message input field, Telegram will start analyzing the link and getting a preview for it. If you prefer to send a particular message without the preview, just tap the (X) to remove it.
Link parsing is managed by the server. This allow the apps to behave in the same way, and to avoid developers manually managing links at every app update (link parsing has to be constantly fixed/changed). It also helps caching the most used links in order to have even faster information.
The link preview is generated server-side. Means, that users send the link to the server, server is fetching infos via API, creates a rich text preview and sends it back to the user. IP of server is shown to the API, not the IP address of the user.
Telegram is using the Open Graph protocol, so it's very easy to update existing web pages to support rich link summaries. Make sure that you can edit the source code of your website and add some meta tags.
<meta property="og:title" content="The title of the page" /> <meta property="og:description" content="Some longer description text" />
Make sure you do not block access to your website. The robots noindex meta tag forbids the Telegram server to fetch information from your website. If you did it once, the Telegram server will remember that it's forbidden to fetch it. Use @WebPageBot to refresh Telegram's link preview server cache.