Embeds

Drop your pages anywhere — a blog sidebar, a post, a newsletter. Fragments are style-free (&embed=1) and resize themselves.

Embed-URL widget

The Embed URL widget puts someone else's page inside yours — a playlist, a map, a reading list from another site.

https only. Anything else is rejected, on save and on render.
Sandboxed. The iframe runs with sandbox="allow-scripts allow-popups" — an opaque origin, so it can't touch your page or your visitors' storage on your domain, and it can't navigate your page.
No tracking extras. Served with a strict referrer policy; the embedded page never sees your visitors' Booklist session.
Some sites refuse to be framed (they send X-Frame-Options) — those simply won't load, which is the site's choice.

There is no raw-HTML widget. If you need richer embeds, ask — new sandboxed widget types get added deliberately.