Question 1

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 2

next/font and next/image — how do they combine for Core Web Vitals?

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 3

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 4

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 5

What changed for next/image defaults in Next.js 16?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes you have used `next/image`.
**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 16.4.2 docs (the `image` reference and the version 16 guide) and the built-in defaults in `next/dist/shared/lib/image-config.js`, and, in the **Verified** section, against `curl` requests to the i

Question 6

What breaks when you upgrade to Next.js 16, and how do you migrate?

Accepted Answer

**Target Audience:** Frontend engineers preparing for Next.js interviews — useful for anyone who has to plan a 15 to 16 upgrade.
**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 16.4.2 upgrade guide shipped in `node_modules/next/dist/docs/` and, in the **Verified** section, against real `next build` and `next start` output from a 16.4.2 lab app written i

Question 7

How does next/image optimize images in Next.js?

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

Question 8

What is next.config.js in Next.js and what are common configurations?

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

Question 9

What is static export (output: 'export') in Next.js and what does it not support?

Accepted Answer

**Target Audience:** Developers preparing for Next.js interviews — assumes the basics of App Router rendering (static vs dynamic routes).
**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 16.4.2 docs shipped with the package and, in the **Verified** section, against lab builds with `output: "export"`, a plain static file server and a Chromium browser.

##

Question 10

How does the Metadata API work in Next.js (static and generateMetadata)?

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

next/font and next/image — how do they combine for Core Web Vitals?

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

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

Medium

What changed for next/image defaults in Next.js 16?

What breaks when you upgrade to Next.js 16, and how do you migrate?

How does next/image optimize images in Next.js?

What is next.config.js in Next.js and what are common configurations?

What is static export (output: 'export') in Next.js and what does it not support?

How does the Metadata API work in Next.js (static and generateMetadata)?

How do you deploy a Next.js app (Vercel vs self-hosted)?

How does Next.js handle SEO compared to a client-rendered SPA?

Hard

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

How do you self-host Next.js across multiple instances (cache handlers, ISR, build IDs)?