Problem Statement
What is special about layout.js in the App Router?
Explanation
layout.js defines UI that wraps page components and persists across route changes within that segment without unmounting or re-rendering, maintaining state and avoiding expensive re-initialization. Layouts are nested, so a layout in app/dashboard/layout.js wraps all dashboard routes while inheriting the root app/layout.js wrapper. Layouts receive a children prop containing the nested page or layout, can fetch data asynchronously, and enable shared UI like navigation bars, sidebars, or headers that don't reset when users navigate between pages in that section.
Practice Sets
This question appears in the following practice sets: