Parallel routes concept in NextJS

Introduction

Parallel routes let you show different parts of a page at the same time without waiting for one to finish loading. This helps make your app faster and smoother.

You want to show a sidebar and main content that load separately.

You have a page with multiple sections that update independently.

You want to keep some UI parts visible while others change.

You want to improve user experience by loading parts in parallel.

You want to avoid full page reloads when switching views.

Syntax

NextJS

app/layout.js
app/(group1)/page.js
app/(group2)/page.js

// In your layout.js
export default function RootLayout({ children, group1, group2 }) {
  return (
    <html>
      <body>
        <div>
          <div>{group1}</div>
          <div>{group2}</div>
          {children}
        </div>
      </body>
    </html>
  )
}

// Use parallel routes by defining folders with parentheses
// and destructuring matching props in the parent layout

Parallel routes use folder names with parentheses to separate routes.

In the parent layout, destructure props matching the folder names and render them like {group1}.

Examples

This layout shows two parallel routes side by side: a sidebar and main content.

NextJS

// Folder structure example:
// app/layout.js
// app/(sidebar)/page.js
// app/(content)/page.js

// app/layout.js
export default function RootLayout({ sidebar, content }) {
  return (
    <html>
      <body>
        <div style={{ display: 'flex' }}>
          <aside style={{ width: '200px' }}>
            {sidebar}
          </aside>
          <main style={{ flex: 1 }}>
            {content}
          </main>
        </div>
      </body>
    </html>
  )
}

Each parallel route has its own page component that renders independently.

NextJS

// app/(sidebar)/page.js
export default function Sidebar() {
  return <nav>Menu items here</nav>
}

// app/(content)/page.js
export default function Content() {
  return <article>Main content here</article>
}

Sample Program

This example shows a page with a sidebar and main content loaded in parallel routes. The sidebar has navigation links, and the content area has a heading and paragraph. They appear side by side.

NextJS

// app/layout.js
export default function RootLayout({ sidebar, content }) {
  return (
    <html lang="en">
      <body>
        <div style={{ display: 'flex', height: '100vh' }}>
          <aside style={{ width: '250px', backgroundColor: '#f0f0f0', padding: '1rem' }}>
            {sidebar}
          </aside>
          <main style={{ flex: 1, padding: '1rem' }}>
            {content}
          </main>
        </div>
      </body>
    </html>
  )
}

// app/(sidebar)/page.js
export default function Sidebar() {
  return (
    <nav aria-label="Main navigation">
      <ul>
        <li><a href="#home">Home</a></li>
        <li><a href="#about">About</a></li>
        <li><a href="#contact">Contact</a></li>
      </ul>
    </nav>
  );
}

// app/(content)/page.js
export default function Content() {
  return (
    <article>
      <h1>Welcome to the content area</h1>
      <p>This section loads separately from the sidebar.</p>
    </article>
  );
}

Important Notes

Parallel routes improve user experience by loading parts of the page independently.

Use meaningful names for your parallel route folders inside parentheses.

Remember to add aria-label for accessibility on navigation elements.

Summary

Parallel routes let you show multiple parts of a page at once.

Use folder names with parentheses and destructure matching props in the layout to place them.

This helps make your app faster and easier to navigate.

Practice

1. What is the main purpose of parallel routes in Next.js?

easy

A. To disable navigation between pages

B. To load pages sequentially one after another

C. To replace client-side routing with server-side only

D. To display multiple parts of a page simultaneously

Solution

1. Step 1: Understand what parallel routes do

   Parallel routes allow showing multiple UI sections at the same time on a page.

2. Step 2: Compare options with this understanding

   Only To display multiple parts of a page simultaneously correctly describes this purpose; others describe unrelated behaviors.

3. Final Answer:

   To display multiple parts of a page simultaneously -> Option D

4. Quick Check:

   Parallel routes = show multiple parts [OK]

Hint: Parallel routes show multiple page parts at once [OK]

Common Mistakes:

• Thinking parallel routes load pages one after another
• Confusing parallel routes with disabling navigation
• Assuming parallel routes replace client-side routing

2. Which folder naming pattern is used to define a parallel route in Next.js?

easy

A. Using parentheses like (route)

B. Using square brackets like [route]

C. Using curly braces like {route}

D. Using angle brackets like <route>

Solution

1. Step 1: Recall folder naming for parallel routes

   Next.js uses parentheses around folder names to mark parallel routes.

2. Step 2: Match options to this rule

   Only Using parentheses like (route) uses parentheses, which is correct for parallel routes.

3. Final Answer:

   Using parentheses like (route) -> Option A

4. Quick Check:

   Parallel routes folder = parentheses [OK]

Hint: Parallel routes folders use parentheses ( ) [OK]

Common Mistakes:

• Using square brackets which are for dynamic routes
• Confusing with curly braces or angle brackets
• Not using any special characters for parallel routes

3. Given this folder structure in Next.js:

app/
  (sidebar)/
    page.jsx
  (content)/
    page.jsx
  layout.jsx

What will happen when the app renders layout.jsx with parallel routes?

medium

A. Both sidebar and content pages render side by side inside layout

B. Only the sidebar page renders, content is ignored

C. Only the content page renders, sidebar is ignored

D. Neither sidebar nor content pages render automatically

Solution

1. Step 1: Understand parallel routes folder names

   Folders named with parentheses define parallel routes that render simultaneously.

2. Step 2: Apply to given structure

   Both (sidebar) and (content) are parallel routes, so their pages render side by side inside layout.

3. Final Answer:

   Both sidebar and content pages render side by side inside layout -> Option A

4. Quick Check:

   Parallel routes render all named folders simultaneously [OK]

Hint: Parentheses folders render together inside layout [OK]

Common Mistakes:

• Thinking only one parallel route renders at a time
• Assuming parallel routes need manual import to render
• Confusing parallel routes with nested routes

4. You have this code in your layout.jsx to render parallel routes:

import { Slot } from 'next/navigation';

export default function Layout() {
  return (
    

      <Slot name="sidebar" />
      <Slot name="content" />
    
  );
}

Why does this code cause an error?

medium

A. Because Slot must be imported from 'next/navigation' as a named import

B. Because <Slot /> should be self-closing JSX tags, not string literals

C. Because parallel routes cannot use Slot components

D. Because Slot requires a default export, not named

Solution

1. Step 1: Check JSX syntax in return statement

   The code uses <Slot name="sidebar" /> as a string literal, not as JSX tags.

2. Step 2: Correct JSX usage

   It should be <Slot name="sidebar" /> without quotes, as a self-closing JSX component.

3. Final Answer:

   Because <Slot /> should be self-closing JSX tags, not string literals -> Option B

4. Quick Check:

   JSX tags must not be strings [OK]

Hint: Use JSX tags, not strings, for [OK]

Common Mistakes:

• Writing JSX tags as strings inside return
• Importing Slot incorrectly
• Thinking Slot can't be used in parallel routes

5. You want to create a page with a sidebar and main content using parallel routes. Which folder structure and code snippet correctly implements this in Next.js?

app/
  (sidebar)/
    page.jsx
  (main)/
    page.jsx
  layout.jsx

And in layout.jsx:

export default function Layout() {
  return (
    

      {/* What goes here? */}
    
  );
}

hard

A. <Slot />

B. <Slot name="content" />
<Slot name="sidebar" />

C. <Slot name="sidebar" />
<Slot name="main" />

D. <Outlet name="sidebar" />
<Outlet name="main" />

Solution

1. Step 1: Match folder names to Slot names

   Folders are named (sidebar) and (main), so Slots must use these exact names.

2. Step 2: Check code snippet for correct Slot usage

   <Slot name="sidebar" /> <Slot name="main" /> uses <Slot name="sidebar" /> and <Slot name="main" />, matching folder names and correct JSX syntax.

3. Final Answer:

   <Slot name="sidebar" /> <Slot name="main" /> -> Option C

4. Quick Check:

   Slot names = folder names [OK]

Hint: Slot names must match parallel route folder names [OK]

Common Mistakes:

• Using wrong Slot names that don't match folders
• Using instead of
• Using only one Slot for multiple parallel routes