A Next.js layout is an essential element of a user interface that can be utilized across multiple pages. It serves as a blueprint for the overall design and structure of a website or application and is responsible for maintaining consistency and coherence throughout the user’s experience.

One of the significant benefits of using a layout is that it preserves the user’s current state and remains interactive during navigation, without the need for re-rendering. This functionality allows for a more seamless and uninterrupted user experience.

To define a layout in Next.js, we can export a React component from a layout.tsx file as the default export. This component should accept a children prop, which serves as a placeholder for the child layout or child page that will be rendered within it. If a child layout exists, it will be rendered within the parent layout and populate the children prop with its own child components.

Similarly, if a child page is being rendered, it will populate the children prop with its own content. This approach allows for a flexible and modular layout system that can be easily customized and reused across multiple pages and components. By defining a layout in this way, developers can create a consistent and cohesive design system that enhances the overall user experience.

An example of a layout for a page that showcases blog page is illustrated in the following code snippet.

TypeScript
JavaScript
app/blog/layout.tsx
  export default function BlogLayout({
  children, // will be a page or nested layout
}: {
  children: React.ReactNode;
}) {
  return (
    <section>
      {/* Include shared UI here e.g. a header, navigation,
          footer or sidebar */}

      {children}
    </section>
  );
}
app/blog/layout.jsx
  export default function BlogLayout({
  children, // will be a page or nested layout
}) {
  return (
    <section>
      {/* Include shared UI here e.g. a header, navigation,
          footer or sidebar */}

      {children}
    </section>
  );
}
Additional information:
  • The layout is a Server Component and cannot be set as a Client Component.
  • Layouts in a route are nested by default, meaning that a parent layout will wrap any child layouts below it using the React children prop.
  • Data fetching is also possible within layouts.
  • We cannot pass data between a parent layout and its children. However, you can fetch the same data multiple times in a route without performance issues because React will automatically deduplicate these requests.

Root Layout (Required)

The root layout is a key component of any application as it defines the overall structure and appearance of the application. This layout is usually defined at the top level of the application directory and is applied to all routes in the application.

By using the root layout, developers are able to modify the original HTML code returned from the server before the browser renders it, which is very useful for optimizing performance and improving user experience.

Additionally, the root layout can be customized to include common elements such as headers, footers, and sidebars, which helps maintain consistency across the application and improves user experience.

TypeScript
JavaScript
app/layout.tsx
  export default function RootLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <html lang="en">
      <body>{children}</body>
    </html>
  );
}
app/layout.jsx
  export default function RootLayout({ children }) {
  return (
    <html lang="en">
      <body>{children}</body>
    </html>
  );
}
Additional information:
  • The app directory must contain the root layout.
  • The root layout must define <html> and <body> tags, because Next.js will not create them automatically.
  • You can use the built-in SEO support to manage <head> HTML elements such as the <title>, <meta> elements.

Nesting Layouts

Layouts can be defined at a more granular level within an application by placing them inside a specific folder, such as app/blog/layout.tsx. These layouts are then applied only to their corresponding route segments, for example, example.com/blog, and are rendered when those segments are active.

By using this approach, developers can create more targeted and tailored layouts that are specific to particular areas of the application. Additionally, layouts defined within a file hierarchy are nested by default, meaning that they can wrap child layouts via their children prop.

TypeScript
JavaScript
app/blog/layout.tsx
  export default function BlogLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return <section>{children}</section>;
}
app/blog/layout.jsx
  export default function BlogLayout({ children }) {
  return <section>{children}</section>;
}

When designing the layout of a web application, it is often necessary to combine multiple layouts to create a richer, more cohesive user interface.

If you combine the above two layouts, the root layout (defined in app/layout.tsx) will wrap the blog layout (defined in app/blog/layout.tsx). This means that all route segments in app/blog/* will be rendered in the blog layout, which in turn will be wrapped by the root layout.

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