Collapsible
Native details and summary provide the interaction; Timeless CSS styles the public accordion anatomy.
What ships in the CSS package?
Tokens, flat primitives, native form styling, and progressive overlay CSS.
Does Collapsible require JavaScript?
No. It uses native details and summary so open state, keyboard access, and find-in-page stay platform-owned.
Can apps replace the icon?
Yes. The public summary anatomy is authored by the app; the default CSS only adds a small indicator.