How to reduce bundle size of react app even further

Question

I am trying to reduce the size of my build file ( main.js ) to 500kb or less.

Initially it was 1.2MB and with some code splitting and webpack I managed to reduce it to around 600kb but I need to reduce it by another 100kb. I am fairly new to webpack and I would appreciate any feedback.

Bellow you can find my webpack.prodduction.config.js

const MiniCssExtractPlugin = require('mini-css-extract-plugin')
const webpack = require('webpack')
const UglifyJSPlugin = require('uglifyjs-webpack-plugin')
const LodashModuleReplacementPlugin = require('lodash-webpack-plugin')

console.log(`Building for: ${process.env.NODE_ENV}`)
module.exports = {
  module: {
    rules: [
      {
        test: /.jsx?$/,
        loader: 'babel-loader',
        exclude: /node_modules/
      }, {
        test: /\.css$/,
        loader: 'style-loader!css-loader'
      }, {
        test: /\.(jpe?g|png|gif|woff|woff2|eot|ttf|svg)(\?[a-z0-9=.]+)?$/,
        loader: 'url-loader?limit=100000' },
      {
        test: /\.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          options: {
            presets: [
              ['@babel/preset-env', {
                useBuiltIns: false,
                modules: false
              }]
            ],
            plugins: [
              '@babel/plugin-transform-runtime',
              '@babel/plugin-proposal-class-properties',
              'inline-react-svg'
            ]
          },
          loader: 'babel-loader'
        }
      },
      {
        test: /\.css$/,
        use: ['style-loader', 'css-loader']
      },
      {
        test: /\.module\.s(a|c)ss$/,
        loader: [
          {
            loader: 'style-loader',
            options: {
              attrs: { class: 'BasebotTag' }
            }
          },
          {
            loader: 'css-loader',
            options: {
              modules: true,
              localIdentName: '[name]__[local]___[hash:base64:5]',
              camelCase: true
            }
          },
          {
            loader: 'sass-loader'
          }
        ]
      },
      {
        test: /\.(woff(2)?|ttf|eot|svg|otf)(\?v=\d+\.\d+\.\d+)?$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: '[name].[ext]',
              outputPath: 'fonts/'
            }
          }
        ]
      },
      {
        test: /\.s(a|c)ss$/,
        exclude: /\.module.(s(a|c)ss)$/,
        loader: [
          {
            loader: 'style-loader',
            options: {
              attrs: { class: 'BasebotTag' }
            }
          },
          'css-loader',
          {
            loader: 'sass-loader'
          }
        ]
      }
    ]
  },
  resolve: {
    extensions: ['.js', '.jsx', '.scss']
  },
  plugins: [
    new UglifyJSPlugin(),
    new LodashModuleReplacementPlugin(),
    new webpack.DefinePlugin({
      'process.env': {
        NODE_ENV: JSON.stringify('production')
      }
    }),
    new webpack.ContextReplacementPlugin(/moment[\/\\]locale$/, /en/),
    new webpack.optimize.ModuleConcatenationPlugin(),
    new MiniCssExtractPlugin({
      filename: '[name].[hash].css',
      chunkFilename: '[id].[hash].css'
    }),
    new LodashModuleReplacementPlugin({
      caching: true,
      cloning: true
    })
  ]
}

EDIT: This is my build script:

"build": "NODE_ENV=production webpack --config webpack.production.config",

Answer 1

You are inlining images and other assets up to 0.1MB (100000 Bytes) with url-loader. It would not take many assets with a size of this upper limit to increase your bundle size significantly. In fact, reducing this limit and un-inlining just one asset of 100KB would mean you meet your target bundle size.

I would suggest only inlining assets that are less than 10KB (10000 Bytes). Everything larger than this can be fetched with an HTTP request when it is needed.

{
  test: /\.(jpe?g|png|gif|woff|woff2|eot|ttf|svg)(\?[a-z0-9=.]+)?$/,
  loader: 'url-loader?limit=10000' }, // <= lower the limit here to 10000
}