Too Long; Didn't Read
Twitter automatically shows the preview of the link in a tweet that you post. Hashnode includes meta tags in every one of the blog posts which is enabling twitter to create that beautiful card. Meta tags are snippets of text that describe a page's content; the meta tags don't appear on the page itself, but only in the page's source code. Platforms like Twitter, Facebook, and LinkedIn make use of these meta tags to display link previews when you add that link on their platform.