It is sometimes useful to embed the contents from one website into another. For example, you may wish to quote a post from a microblogging site like Twitter, Threads, BlueSky, or Mastodon.
All of them offer an "embed" button which will copy a snippet of code for you to paste into your website. Here's how they compare:
In my considered opinion, BlueSky is the only modern service which does embedding correctly. The full text is placed in a <blockquote>, with a link back, links to any attached content, and the datetime of the post. It is then progressively enhanced with JS to show the full content:
It might be nice to have a smidge more semantics in there - but the overall experience is good. Hashtags, links, and user mentions could probably be linked. If the JS doesn't load, the text and essential information is available.
I'm not a fan of the Mastodon embed. It's an <iframe> and nothing else. If the service goes down, the content of the message isn't preserved.