For AI agents: the complete documentation index is available at https://lazygophers.github.io/pamphlet/en/llms.txt, the full documentation bundle is available at https://lazygophers.github.io/pamphlet/en/llms-full.txt, and this page is available as Markdown at https://lazygophers.github.io/pamphlet/en/write/components/collapse.md.
Pamphlet
  • English

      • Collapsibles

      What it is

      A block that starts closed and opens on click. For detail most readers don't need: full configuration, raw logs, appendices.

      How to write it

      :::collapse[Show the details]
Hidden content goes here.
:::

:::collapse[This one starts open]{open}
`{open}` starts it expanded.
:::
      LabelAttributes
      requiredopen

      The label is required; without it you get DIR-204. The reason is concrete: with JavaScript off this degrades to a native <details>, and the label is its <summary> — without one there is nothing to click.

      What comes out

      A disclosure row with a triangle.

      With JavaScript off it is a native <details> and still opens; {open} maps to <details open>. This is the cleanest degradation of the interactive directives, because the browser has the element built in.

      With JavaScript it does one extra thing: opening writes the label into the URL, so you can send someone the opened state.

      Traps

      • Don't hide anything important — same reason as tabs: the content is always in the DOM and searchable
      • Save {open} for "most people need this but it takes space". A collapsible that starts open only offers the ability to close it