Output webpack stats in Next.js

To output the webpack stats JSON file on Next.js, use webpack-stats-plugin.

Install

npm install --save-dev webpack-stats-plugin
yarn add --dev webpack-stats-plugin
pnpm add -D webpack-stats-plugin

Configure

The webpack stats JSON data and structure are controlled by the webpack config stats options. The RelativeCI agent extracts data from assets, chunks, and modules entries. The corresponding stats options are required:

next.config.js
const { StatsWriterPlugin } = require('webpack-stats-plugin')
module.exports = {
webpack: (config, options) => {
const { dev, isServer } = options;
// Output webpack stats JSON file only for
// client-side/production build
if (!dev && !isServer) {
config.plugins.push(
new StatsWriterPlugin({
filename: '../webpack-stats.json',
stats: {
assets: true,
chunks: true,
modules: true
}
})
);
}
return config;
}
};

Exclude assets or modules

If you need to exclude particular assets or modules, you can use the webpack stats excludeAssets or excludeModules configuration options:

next.config.js
const { StatsWriterPlugin } = require('webpack-stats-plugin')
module.exports = {
webpack: (config, options) => {
const { dev, isServer } = options;
// Output webpack stats JSON file only for
// client-side/production build
if (!dev && !isServer) {
config.plugins.push(
new StatsWriterPlugin({
filename: '../webpack-stats.json',
stats: {
assets: true,
chunks: true,
modules: true,
// Exclude webpack-stats.json asset
excludeAssets: [/webpack-stats.json/],
// Exclude custom-module.js module
excludeModules: [/custom-module.js/]
}
})
);
}
return config;
}
};

Advanced transforms

You can use the webpack-stats-plugin transform option for more advanced cases to extract and manipulate the webpack stats result.

Optimize the JSON file size

The module's data can get large for projects with a high number of modules. To optimize the webpack stats JSON file size, you can use the transform property to output only the data required by the RelativeCI agent or bundle-stats:

Install @bundle-stats/plugin-webpack-filter

npm install --save-dev @bundle-stats/plugin-webpack-filter
yarn add --dev @bundle-stats/plugin-webpack-filter
pnpm add -D @bundle-stats/plugin-webpack-filter

Filter the webpack stats data

next.config.js
const { StatsWriterPlugin } = require('webpack-stats-plugin')
const filterWebpackStats = require(
'@bundle-stats/plugin-webpack-filter'
).default;
module.exports = {
webpack: (config, options) => {
const { dev, isServer } = options;
// Output webpack stats JSON file only for
// client-side/production build
if (!dev && !isServer) {
config.plugins.push(
new StatsWriterPlugin({
filename: '../webpack-stats.json',
stats: {
assets: true,
chunks: true,
modules: true,
},
transform: (webpackStats) => {
const filteredSource = filterWebpackStats(webpackStats);
return JSON.stringify(filteredSource);
}
})
);
}
return config;
}
};

Resources


To avoid issues with other tools that check if the repository has uncommitted changes or if you are publishing your project as an npm package, consider adding the generated webpack stats file to .gitignore/.npmignore.

.gitignore
webpack-stats.json
.npmignore
webpack-stats.json


Need help?Contact us via email, Twitter, or GitHub!