Webpack Stats Plugin

1.1.3 verified Sat Apr 25 auth: no javascript

A webpack plugin that ingests the compiler's stats object, transforms it, and writes a JSON file (typically 'stats.json') to the output directory. Version 1.1.3 is the current stable release, updated primarily with patch-level maintenance. Key differentiator: it is a dedicated, minimal stats-file writer without the overhead of full-featured analysis tools. It supports custom transforms (sync or Promise), selective field filtering, and works with webpack 4 and 5. Maintained by Formidable Labs.

Common errors

error Error: Cannot find module 'webpack-stats-plugin' ↓

cause Package not installed or installed only as a dev dependency but not required correctly.

fix

Run npm install --save-dev webpack-stats-plugin and ensure it's in node_modules.

error TypeError: webpack_stats_plugin_1.StatsWriterPlugin is not a constructor ↓

cause Wrong import syntax, likely using default import with CommonJS or incorrect require.

fix

Use const { StatsWriterPlugin } = require('webpack-stats-plugin'); (named export) or import { StatsWriterPlugin } from 'webpack-stats-plugin'; in ESM.

error Stats file is empty or missing expected fields ↓

cause The `fields` option restricts included fields; defaults to `["assetsByChunkName"]`.

fix

Set fields: null to include all stats fields, or explicitly include needed fields like ['assets', 'chunks', 'modules'].

error TypeError: data.toJson is not a function ↓

cause The transform function receives the raw stats object directly (not a compiler stats instance) in recent versions.

fix

Access data directly as the transformed JSON object; do not call .toJson() on it. For custom stats generation, use the stats option described above.

Warnings

gotcha The `fields` option defaults to `["assetsByChunkName"]`, so by default not all stats properties are written. ↓

fix Set `fields: null` to include all stats fields, or provide an array of field names you need.

gotcha The `filename` can be a function returning a string, but the function receives the compilation data and must be synchronous. ↓

fix If using a function for `filename`, ensure it returns a string synchronously. For async filename generation, use the `transform` option.

gotcha The plugin does not automatically emit the stats file in development mode or when `emit: false`. By default `emit: true`. ↓

fix If you don't see the stats file, ensure you have `emit: true` (the default) or check that the webpack output path is correct.

gotcha When using webpack 5 with `output.clean: true`, the stats file may be deleted on rebuild if not emitted correctly. ↓

fix Ensure `emit` is `true` (default) and that `filename` is within the output path. The plugin adds the file to the compiler's assets.

Install

npm install webpack-stats-plugin

yarn add webpack-stats-plugin

pnpm add webpack-stats-plugin

Imports

StatsWriterPlugin

wrong

const StatsWriterPlugin = require('webpack-stats-plugin');

correct

const { StatsWriterPlugin } = require('webpack-stats-plugin');

Named export via CommonJS. ESM support not provided; using a default import will fail.

StatsWriterPlugin (ESM)

wrong

import StatsWriterPlugin from 'webpack-stats-plugin';

correct

import { StatsWriterPlugin } from 'webpack-stats-plugin';

Named export. Default import yields undefined.

None
wrong
```
const statsPlugin = require('webpack-stats-plugin');
```
correct
```
const { StatsWriterPlugin } = require('webpack-stats-plugin');
```
The package only exports StatsWriterPlugin; accessing it via a default require gives an object with the named export.

Quickstart

Basic webpack config that writes the full stats object to a file named 'stats.json' with formatting.

const { StatsWriterPlugin } = require('webpack-stats-plugin');

module.exports = {
  // ... other config
  plugins: [
    new StatsWriterPlugin({
      filename: 'stats.json',
      fields: null, // include all fields
      transform(data) {
        return JSON.stringify(data, null, 2);
      },
    }),
  ],
};