Intercepting routes (.) in NextJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of intercepting routes in Next.js?

Intercepting routes lets you show parts of a page or UI without leaving the current page. It helps create smooth transitions and nested layouts by loading content inside existing layouts.

beginner

How do you define an intercepting route in Next.js App Router?

You add parentheses around the folder name in the app directory, like (modal), to mark it as an intercepting route. This folder can then load UI inside the current page without full navigation.

intermediate

What is the difference between a normal route and an intercepting route in Next.js?

A normal route replaces the whole page content. An intercepting route loads content inside the current page layout, letting you keep parts of the UI visible while changing others.

intermediate

Can intercepting routes be used to create modals or sidebars in Next.js?

Yes! Intercepting routes are perfect for modals or sidebars because they let you open these UI parts without leaving the current page or losing state.

beginner

What folder naming pattern signals an intercepting route in Next.js App Router?

Folders with parentheses, like (modal) or (sidebar), are intercepting routes. The parentheses tell Next.js to treat them as UI overlays or nested content inside the current page.

How do you mark a folder as an intercepting route in Next.js App Router?

A Wrap the folder name in parentheses, e.g., (modal)

B Prefix the folder name with an underscore, e.g., _modal

C Add a file named intercept.js inside the folder

D Use a special config file in the folder

In Next.js App Router, folders wrapped in parentheses are intercepting routes.

What is a common use case for intercepting routes?

A Loading a full new page

B Changing the URL without changing content

C Preloading images

D Showing a modal without leaving the current page

Intercepting routes let you show modals or sidebars inside the current page.

What happens when you navigate to an intercepting route?

A The browser opens a new tab

B The whole page reloads

C Only the content inside the intercepting route updates

D The URL does not change

Only the part inside the intercepting route updates, keeping the rest of the page intact.

Which folder name is an example of an intercepting route?

A (modal)

B modal_intercept

C _modal

D modal

Parentheses around the folder name mark it as an intercepting route.

Why use intercepting routes instead of normal routes for UI overlays?

A To reload the entire page faster

B To keep the current page visible and only add overlays

C To disable navigation

D To hide the URL bar

Intercepting routes keep the current page visible and add overlays like modals or sidebars.

Explain how intercepting routes work in Next.js and why they are useful.

Think about how you open a popup without leaving a webpage.

Describe the difference between a normal route and an intercepting route in Next.js.

Compare full page reload vs partial UI update.

Practice

1. What is the main purpose of intercepting routes in Next.js App Router?

easy

A. To force server-side rendering on every route

B. To reload the entire page on every navigation

C. To disable client-side navigation

D. To add UI parts without leaving the current page

Solution

1. Step 1: Understand intercepting routes concept

   Intercepting routes allow adding UI parts while staying on the same page, avoiding full reloads.

2. Step 2: Compare options with concept

   Options suggesting page reloads, disabling navigation, or forcing server-side rendering contradict the idea of smooth UI updates without full reloads.

3. Final Answer:

   To add UI parts without leaving the current page -> Option D

4. Quick Check:

   Intercepting routes = add UI parts without leaving page [OK]

Hint: Intercepting routes keep you on the page while adding UI [OK]

Common Mistakes:

• Thinking intercepting routes reload the whole page
• Confusing intercepting routes with disabling navigation
• Assuming intercepting routes force server rendering

2. Which folder name syntax is used to create an intercepting route in Next.js App Router?

easy

A. @modal

B. modal

C. (modal)

D. [modal]

Solution

1. Step 1: Recall folder naming for intercepting routes

   Intercepting routes use parentheses around folder names, like (modal), to mark them as intercepting.

2. Step 2: Evaluate options

   (modal) uses parentheses correctly. @modal uses @ for parallel routes, modal omits parentheses for regular routes, and [modal] uses square brackets for dynamic routes.

3. Final Answer:

   (modal) -> Option C

4. Quick Check:

   Intercepting route folder = parentheses [OK]

Hint: Intercepting routes use (folderName) syntax [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Omitting parentheses for intercepting routes
• Confusing @ folders with intercepting route folders

3. Given this folder structure in Next.js App Router:
app/(modal)/page.tsx
What happens when you navigate to a route inside (modal)?

medium

A. The modal UI appears without leaving the current page

B. The entire page reloads and shows only the modal content

C. Navigation fails with a 404 error

D. The modal opens in a new browser tab

Solution

1. Step 1: Understand intercepting route behavior

   Routes inside (modal) folders add UI parts like modals without leaving the current page.

2. Step 2: Analyze navigation effect

   Navigation triggers modal UI overlay, not a full page reload or error.

3. Final Answer:

   The modal UI appears without leaving the current page -> Option A

4. Quick Check:

   Navigation in (modal) = modal UI without reload [OK]

Hint: Routes in (modal) show UI without page reload [OK]

Common Mistakes:

• Expecting full page reload on modal route
• Thinking navigation causes errors
• Assuming modal opens in new tab

4. You wrote this intercepting route folder: app/@(sidebar)/page.tsx. Why does it cause a build error?

medium

A. Parentheses cannot be combined with @ in folder names

B. The folder name must be all lowercase

C. You need to add a layout.tsx file inside the folder

D. The file extension should be .jsx, not .tsx

Solution

1. Step 1: Check folder naming rules for intercepting routes

   Parentheses indicate intercepting routes; @ folders are separate special folders. Combining them is invalid syntax.

2. Step 2: Identify cause of build error

   Using @(sidebar) mixes two folder naming conventions, causing build failure.

3. Final Answer:

   Parentheses cannot be combined with @ in folder names -> Option A

4. Quick Check:

   Invalid folder name combining ( ) and @ causes error [OK]

Hint: Don't mix ( ) and @ in folder names [OK]

Common Mistakes:

• Thinking lowercase folder name fixes error
• Assuming missing layout.tsx causes build error
• Confusing file extension with folder naming

5. You want to show a sidebar UI on some pages without leaving the current page. Which folder structure correctly implements this intercepting route in Next.js App Router?

hard

A. app/(sidebar)/page.tsx without layout.tsx

B. app/(sidebar)/page.tsx with a layout.tsx inside (sidebar) wrapping children

C. app/@sidebar/page.tsx with page.tsx only

D. app/sidebar/page.tsx with a layout.tsx inside sidebar wrapping children

Solution

1. Step 1: Identify correct intercepting route folder

   Using parentheses (sidebar) marks it as an intercepting route folder.

2. Step 2: Confirm layout usage for UI wrapping

   Adding layout.tsx inside (sidebar) allows wrapping children with sidebar UI, enabling partial UI updates.

3. Step 3: Evaluate other options

   app/sidebar/page.tsx with a layout.tsx inside sidebar wrapping children lacks parentheses, so it's a normal route. app/@sidebar/page.tsx with page.tsx only uses @ which is for special folders, not intercepting routes. app/(sidebar)/page.tsx without layout.tsx misses layout.tsx, so sidebar UI won't wrap children properly.

4. Final Answer:

   app/(sidebar)/page.tsx with a layout.tsx inside (sidebar) wrapping children -> Option B

5. Quick Check:

   Intercepting route with layout wraps UI correctly [OK]

Hint: Use (folder) plus layout.tsx to wrap UI in intercepting routes [OK]

Common Mistakes:

• Omitting layout.tsx inside intercepting route folder
• Using normal folder instead of (folder) for intercepting route
• Confusing @ folders with intercepting route folders