How to Analyze Next.js App Bundles

In this blog post, we will learn how to analyze the code bundles generated in a Next.js app. Next.js provides us with a useful way to analyze these bundles, allowing us to understand what’s inside them and optimize our application’s performance.

To get started, open the package.json file of your Next.js app and add the following three commands to the scripts section:

"analyze": "cross-env ANALYZE=true next build",
"analyze:server": "cross-env BUNDLE_ANALYZE=server next build",
"analyze:browser": "cross-env BUNDLE_ANALYZE=browser next build"

Your updated package.json file should look like this:

{
  "name": "firstproject",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "dev": "next",
    "build": "next build",
    "start": "next start",
    "analyze": "cross-env ANALYZE=true next build",
    "analyze:server": "cross-env BUNDLE_ANALYZE=server next build",
    "analyze:browser": "cross-env BUNDLE_ANALYZE=browser next build"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "next": "^9.1.2",
    "react": "^16.11.0",
    "react-dom": "^16.11.0"
  }
}

Next, we need to install two packages by running the following command:

npm install --dev cross-env @next/bundle-analyzer

Once the packages are installed, create a next.config.js file in the root of your project and add the following code:

const withBundleAnalyzer = require('@next/bundle-analyzer')({
  enabled: process.env.ANALYZE === 'true'
})

module.exports = withBundleAnalyzer({})

Now, it’s time to analyze the bundles. Run the command npm run analyze in your terminal.

This command will open two pages in your browser - one for the client bundles and one for the server bundles. These pages will provide you with valuable insights into what’s taking up the most space in your bundles.

Additionally, the sidebar in the analyzer tool allows you to exclude bundles, making it easier to visualize the smaller ones.

Analyzing your Next.js app bundles in this way is incredibly useful for optimizing performance and identifying potential areas for improvement.

Remember to make use of this powerful tool to gain a deeper understanding of your application’s bundle composition and make informed decisions to enhance its performance.

tags:Next.js, bundle analysis, code optimization, performance optimization