Question 1

How do environment variables work in Next.js (the NEXT_PUBLIC_ prefix)?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified block

Question 2

How do metadata files like favicon.ico, icon, opengraph-image and manifest work in Next.js?

Accepted Answer

**Target Audience:** Beginners preparing for Next.js interviews — basic HTML (what the head element is) helps.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against a lab app built with `next build`, served with `next start` and inspected with `curl`.

## 1. Why This Even Matters — A

Question 3

How does client-side navigation work in Next.js (next/link and useRouter)?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against real output from a build, a running server or a real browser.

## 1. Why This Even Matters — A Story First

Question 4

What is Next.js and what problems does it solve?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified block

Question 5

What is the difference between the /public folder and imported assets in Next.js?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified block

Question 6

What happens when you run next dev, next build and next start?

Accepted Answer

**Target Audience:** Beginners preparing for Next.js interviews — no prior Next.js knowledge assumed.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against a real `create-next-app@16.4.2` project run under all three commands and probed with `curl`.

## 1. Why This Even Matters — A St

Question 7

How do you read the current URL in a Next.js Client Component (usePathname, useSearchParams, useParams)?

Accepted Answer

**Target Audience:** Beginners preparing for Next.js interviews — assumes basic React hooks and the idea of Server vs Client Components.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against lab builds, `curl` and a real Chromium browser.

## 1. Why This Even Matters — A Story First

Question 8

How do sitemap.ts and robots.ts work in Next.js?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified block

Question 9

How do you create a new Next.js app, and what is in the project structure?

Accepted Answer

**Target Audience:** Beginners preparing for Next.js interviews — no prior Next.js knowledge assumed, basic React helps.
**Difficulty:** Easy

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js 16.4.2 docs shipped with the package and, in the **Verified** section, against a real run of `create-next-app@16.4.2`, `next build` and `next start` in a lab.

## 1. Why This Even Matters

Question 10

What is the route segment config in Next.js (dynamic, revalidate, runtime)?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity.
**Difficulty:** Medium

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified bloc

NEXT.JSDECODED.

Easy

How do environment variables work in Next.js (the NEXT_PUBLIC_ prefix)?

How do metadata files like favicon.ico, icon, opengraph-image and manifest work in Next.js?

How does client-side navigation work in Next.js (next/link and useRouter)?

What is Next.js and what problems does it solve?

What is the difference between the /public folder and imported assets in Next.js?

What happens when you run next dev, next build and next start?

How do you read the current URL in a Next.js Client Component (usePathname, useSearchParams, useParams)?

How do sitemap.ts and robots.ts work in Next.js?

Medium

What is the route segment config in Next.js (dynamic, revalidate, runtime)?

What is the difference between Server Components and Client Components in Next.js?

What is Draft Mode in Next.js and how does it work with a headless CMS?

What is generateStaticParams in Next.js and how does it enable SSG for dynamic routes?

How does Next.js decide between static and dynamic rendering at build time?

What is the difference between static and dynamic rendering in the Next.js App Router?

What is the difference between getServerSideProps/getStaticProps and App Router data fetching?

What makes a route dynamic in the Next.js App Router?

Hard

What changed about caching defaults in Next.js 15?

How do you build a multi-tenant Next.js app with subdomain routing?

What are Cache Components in Next.js 16 and how does the 'use cache' directive work?

What is Partial Prerendering (PPR) in Next.js?

What is the Router Cache in Next.js and what are its implications?

What are the caching layers in Next.js (Request Memoization, Data Cache, Full Route Cache, Router Cache)?

How do you implement dynamic Open Graph images in Next.js (ImageResponse)?

What is the Full Route Cache in Next.js?