Create Next App setup in NextJS - Performance & Optimization

Performance: Create Next App setup

MEDIUM IMPACT

This affects the initial page load speed and bundle size by determining how the app is scaffolded and dependencies are included.

Setting up a new Next.js project for fast initial load

NextJS

npx create-next-app@latest my-app --use-npm
# Creates a minimal starter with only essential dependencies

Minimal setup avoids extra dependencies and large example code, reducing bundle size and speeding up first paint.

📈 Performance Gainsaves 300kb+ in bundle, reduces blocking time by 200ms

Setting up a new Next.js project for fast initial load

NextJS

npx create-next-app@latest my-app --use-npm --example with-redux-toolkit
# This installs a large example with many dependencies not needed initially

Including large example templates adds unnecessary dependencies and code, increasing bundle size and slowing initial load.

📉 Performance Costadds 300kb+ to initial bundle, blocks rendering for 200-300ms longer

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Minimal Create Next App setup	Minimal DOM nodes	1 reflow on initial load	Low paint cost	[OK] Good
Create Next App with large example template	More DOM nodes from example	Multiple reflows due to heavy scripts	Higher paint cost	[X] Bad

Rendering Pipeline

The Create Next App setup determines the initial JavaScript and CSS loaded, affecting style calculation, layout, and paint stages during first load.

→Style Calculation

→Layout

→Paint

→Script Evaluation

⚠️ BottleneckScript Evaluation due to large bundles from unnecessary dependencies

Core Web Vital Affected

LCP

This affects the initial page load speed and bundle size by determining how the app is scaffolded and dependencies are included.

Optimization Tips

1Start with the minimal Create Next App template to keep bundles small.

2Avoid adding large example templates that include unnecessary dependencies.

3Use lazy loading and code splitting to reduce initial script evaluation time.

Performance Quiz - 3 Questions

What is a performance downside of using a large example template when creating a Next.js app?

A It improves caching automatically

B It increases the initial bundle size and delays page load

C It reduces the number of DOM nodes

D It decreases script evaluation time

DevTools: Performance

How to check: Open Chrome DevTools > Performance tab > Record page load > Look at Main thread for script evaluation and rendering times

What to look for: Long scripting tasks and delayed first contentful paint indicate heavy initial bundles from setup

Practice

1. What does the command npx create-next-app@latest do when setting up a Next.js project?

easy

A. It creates a new Next.js project with default settings and dependencies installed.

B. It updates an existing Next.js project to the latest version.

C. It runs the Next.js development server immediately.

D. It installs only React without Next.js features.

Solution

1. Step 1: Understand the purpose of npx create-next-app@latest

   This command scaffolds a new Next.js project with all necessary files and dependencies.

2. Step 2: Differentiate from other commands

   It does not update or run servers; it only creates a fresh project setup.

3. Final Answer:

   It creates a new Next.js project with default settings and dependencies installed. -> Option A

4. Quick Check:

   Project creation = A [OK]

Hint: Remember: create-next-app sets up a new project [OK]

Common Mistakes:

• Confusing create-next-app with update commands
• Thinking it runs the server automatically
• Assuming it installs only React

2. Which of the following is the correct command to start the Next.js development server after creating the app?

easy

A. npm start

B. npm run dev

C. next dev

D. node server.js

Solution

1. Step 1: Identify the standard Next.js development command

   After setup, npm run dev starts the development server with hot reload.

2. Step 2: Compare with other commands

   npm start is usually for production, next dev is a lower-level command but not standard npm script, and node server.js is unrelated here.

3. Final Answer:

   npm run dev -> Option B

4. Quick Check:

   Dev server start = A [OK]

Hint: Use npm run dev to start Next.js dev server [OK]

Common Mistakes:

• Using npm start instead of npm run dev
• Trying to run node server.js without setup
• Confusing next dev with npm scripts

3. After running npx create-next-app@latest my-app and then cd my-app followed by npm run dev, what will you see when you open http://localhost:3000 in your browser?

medium

A. A blank white page with no content.

B. A list of files in the project directory.

C. An error message saying the server is not running.

D. A Next.js welcome page with links to documentation and examples.

Solution

1. Step 1: Understand default Next.js app behavior

   The default Next.js app shows a welcome page with helpful links after setup and running dev server.

2. Step 2: Eliminate other options

   Blank page means no content, error means server not running, and file list is not default behavior.

3. Final Answer:

   A Next.js welcome page with links to documentation and examples. -> Option D

4. Quick Check:

   Default page = B [OK]

Hint: Default Next.js app shows welcome page on localhost:3000 [OK]

Common Mistakes:

• Expecting a blank page instead of welcome content
• Assuming server is not running after npm run dev
• Thinking file list is shown by default

4. You ran npx create-next-app@latest but when you try npm run dev, you get an error: command not found: next. What is the likely cause?

medium

A. You ran npm run dev outside the project folder.

B. You need to restart your computer after installation.

C. You forgot to install Node.js on your system.

D. Your internet connection is down.

Solution

1. Step 1: Analyze the error message

   The error command not found: next usually means the Next.js binary is not found in current folder's node_modules.

2. Step 2: Check common causes

   This happens if you run npm run dev outside the project directory where dependencies are installed.

3. Final Answer:

   You ran npm run dev outside the project folder. -> Option A

4. Quick Check:

   Run commands inside project folder = C [OK]

Hint: Always run npm scripts inside your project folder [OK]

Common Mistakes:

• Assuming Node.js is not installed when it is
• Restarting computer unnecessarily
• Blaming internet connection for local command errors

5. You want to create a new Next.js app named blog but also want to use TypeScript from the start. Which command should you run?

hard

A. npx create-next-app@latest blog --use-typescript

B. npx create-next-app@latest blog -ts

C. npx create-next-app@latest blog --typescript

D. npx create-next-app@latest blog --ts

Solution

1. Step 1: Recall official flag for TypeScript setup

   The official flag to create a Next.js app with TypeScript is --typescript.

2. Step 2: Verify other options

   Short flags like -ts or --ts are not recognized, and --use-typescript is invalid.

3. Final Answer:

   npx create-next-app@latest blog --typescript -> Option C

4. Quick Check:

   Use --typescript flag = D [OK]

Hint: Use --typescript flag to create TS Next.js app [OK]

Common Mistakes:

• Using incorrect or shorthand flags
• Assuming TypeScript is default without flag
• Trying unsupported flag names