Next.js, The Docs: Layouts and Templates

Currently Reading: Layouts and Templates, from the Next.js Docs.

In Next.js 14+, both layouts and templates serve to wrap your application’s UI, but their key difference lies in their behavior during navigation and rendering. Let’s dive into their purposes, use cases, and how they can improve your application’s structure.

Layouts: Persistent and Efficient

A layout is designed to persist between page navigations, allowing elements such as sidebars or headers to remain interactive and maintain their state without re-rendering when the user moves to a new page. This behavior enhances performance by preventing unnecessary re-renders of components that remain static across different routes. In Next.js, layouts are typically used to create shared UI elements across multiple routes, offering a seamless user experience.

Use case: Imagine you have a dashboard with a persistent sidebar and a header that contains a user’s profile information. The sidebar and header should not disappear or reload every time the user navigates to a different section of the dashboard (e.g., /dashboard/settings). Instead, the content changes dynamically while the sidebar and header remain constant. This is where a layout shines.

Example:

typescriptCopy
// app/dashboard/layout.tsx
export default function DashboardLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <section>
      <nav> {/* Sidebar */} </nav>
      <header> {/* Header */} </header>
      {children} {/* Page content */}
    </section>
  );
}

Here, the DashboardLayout is responsible for rendering shared components like the navigation and header, while the children represent the page content that changes dynamically without affecting the persistent UI.

Templates: Dynamic Re-renders on Navigation

Unlike layouts, templates are designed to re-render components on navigation. Templates recreate their child elements, which means that the DOM is rebuilt and state is reset when the user navigates to a different route. This behavior is useful when you need to resynchronize data or reset component states between navigations.

Use case: If you have a form that a user fills out on one page, but you want the form to reset each time the user revisits that page, a template would be more appropriate. Similarly, if you have a component relying on useEffect that should be re-synced when navigating between routes, a template ensures this happens by recreating the child components.

Example:

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// app/template.tsx
export default function Template({ children }: { children: React.ReactNode }) {
  return <div>{children}</div>;
}

This template will reset its state and child components whenever a new navigation occurs, ensuring that the UI is refreshed with each visit.

Choosing Between Layouts and Templates

• Use a Layout when you want components to persist across navigations and maintain their state. This is ideal for headers, sidebars, or footers that remain constant as the user navigates through different routes.
• Use a Template when you need components to re-render on navigation, resetting their state and effects. This is useful for forms, dynamic data fetching, or components that need to synchronize with route changes.

Nesting and Combining Layouts and Templates

In Next.js, you can nest layouts to create complex UIs. For example, a root layout might wrap an entire dashboard, while a child layout could wrap specific sections of the dashboard. Additionally, templates can be placed between layouts and their children to reset specific portions of the UI without affecting the entire layout structure.

Example:

htmlCopy
<RootLayout>
  <DashboardLayout>
    <template> {/* Page content */} </template>
  </DashboardLayout>
</RootLayout>

Here, the RootLayout remains persistent across the entire app, the DashboardLayout wraps the dashboard’s UI, and the Template resets its contents on each navigation within the dashboard.

Conclusion

The main distinction between layouts and templates is how they handle persistence and re-rendering. Layouts are for maintaining persistent UI elements across routes to improve performance, while templates are for cases where state and UI elements need to be reset or re-rendered upon navigation. By understanding when to use layouts or templates, you can create efficient, dynamic applications that offer both stability and responsiveness depending on the needs of the specific UI components.