# Technical Documentation: webpack/webpack-bundle-analyzer > ℹ️ **Provenance:** Multi-Tier Ingestion · [CodeWiki Reference](https://codewiki.google/github.com/webpack/webpack-bundle-analyzer) ### Overview (`README.md`) [![npm][npm]][npm-url] [![node][node]][node-url] [![tests][tests]][tests-url] [![downloads][downloads]][downloads-url]

Webpack Bundle Analyzer

Visualize size of webpack output files with an interactive zoomable treemap.

Install

```bash # NPM npm install --save-dev webpack-bundle-analyzer # Yarn yarn add -D webpack-bundle-analyzer ```

Usage (as a plugin)

```js const { BundleAnalyzerPlugin } = require("webpack-bundle-analyzer"); module.exports = { plugins: [new BundleAnalyzerPlugin()], }; ``` It will create an interactive treemap visualization of the contents of all your bundles. This module will help you: 1. Realize what's _really_ inside your bundle 2. Find out what modules make up the most of its size 3. Find modules that got there by mistake 4. Optimize it! And the best thing is it supports minified bundles! It parses them to get real size of bundled modules. And it also shows their gzipped, Brotli, or Zstandard sizes!

Options (for plugin)

```js new BundleAnalyzerPlugin(options?: object) ``` | Name | Type | Description | | :------------------------: | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------: | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **`analyzerMode`** | One of: `server`, `static`, `json`, `disabled` | Default: `server`. In `server` mode analyzer will start HTTP server to show bundle report. In `static` mode single HTML file with bundle report will be generated. In `json` mode single JSON file with bundle report will be generated. In `disabled` mode you can use this plugin to just generate Webpack Stats JSON file by setting `generateStatsFile` to `true`. | | **`analyzerHost`** | `{String}` | Default: `127.0.0.1`. Host that will be used in `server` mode to start HTTP server. | | **`analyzerPort`** | `{Number}` or `auto` | Default: `8888`. Port that will be used in `server` mode to start HTTP server. If `analyzerPort` is `auto`, the operating system will assign an arbitrary unused port | | **`analyzerUrl`** | `{Function}` called with `{ listenHost: string, listenHost: string, boundAddress: server.address}`. [server.address comes from Node.js](https://nodejs.org/api/net.html#serveraddress) | Default: `http://${listenHost}:${boundAddress.port}`. The URL printed to console with server mode. | | **`reportFilename`** | `{String}` | Default: `report.html`. Path to bundle report file that will be generated in `static` mode. It can be either an absolute path or a path relative to a bundle output directory (which is output.path in webpack config). | | **`reportTitle`** | `{String\|function}` | Default: function that returns pretty printed current date and time. Content of the HTML `title` element; or a function of the form `() => string` that provides the content. | | **`defaultSizes`** | One of: `stat`, `parsed`, `gzip`, `brotli` | Default: `parsed`. Module sizes to show in report by default. [Size definitions](#size-definitions) section describes what these values mean. | | **`compressionAlgorithm`** | One of: `gzip`, `brotli`, `zstd` | Default: `gzip`. Compression type used to calculate the compressed module sizes. | | **`openAnalyzer`** | `{Boolean}` | Default: `true`. Automatically open report in default browser. | | **`generateStatsFile`** | `{Boolean}` | Default: `false`. If `true`, webpack stats JSON file will be generated in bundle output directory | | **`statsFilename`** | `{String}` | Default: `stats.json`. Name of webpack stats JSON file that will be generated if `generateStatsFile` is `true`. It can be either an absolute path or a path relative to a bundle output directory (which is output.path in webpack config). | | **`statsOptions`** | `null` or `{Object}` | Default: `null`. Options for `stats.toJson()` method. For example you can exclude sources of your modules from stats file with `source: false` option. [See more options here](https://webpack.js.org/configuration/stats/). | | **`excludeAssets`** | `{null\|pattern\|pattern[]}` where `pattern` equals to `{String\|RegExp\|function}` | Default: `null`. Patterns that will be used to match against asset names to exclude them from the report. If pattern is a string it will be converted to RegExp via `new RegExp(str)`. If pattern is a function it should have the following signature `(assetName: string) => boolean` and should return `true` to _exclude_ matching asset. If multiple patterns are provided asset should match at least one of them to be excluded. | | **`logLevel`** | One of: `info`, `warn`, `error`, `silent` | **Deprecated**. Default: `info`. Used to control how much details the plugin outputs. Please use webpack's [`infrastructureLogging`](https://webpack.js.org/configuration/infrastructureLogging/) configuration instead. | ### Absolute output paths `reportFilename` and `statsFilename` can be absolute paths. Use absolute paths when you want the generated report or stats file to be written outside webpack's `output.path`. Relative paths are resolved against the bundle output directory. ```js const path = require("node:path"); const { BundleAnalyzerPlugin } = require("webpack-bundle-analyzer"); module.exports = { plugins: [ new BundleAnalyzerPlugin({ analyzerMode: "static", reportFilename: path.resolve(__dirname, "reports/report.html"), generateStatsFile: true, statsFilename: path.resolve(__dirname, "reports/stats.json"), }), ], }; ```

Usage (as a CLI utility)

You can analyze an existing bundle if you have a webpack stats JSON file. You can generate it using `BundleAnalyzerPlugin` with `generateStatsFile` option set to `true` or with this simple command: ```bash webpack --profile --json > stats.json ``` If you're on Windows and using PowerShell, you can generate the stats file with this command to [avoid BOM issues](https://github.com/webpack/webpack-bundle-analyzer/issues/47): ``` webpack --profile --json | Out-file 'stats.json' -Encoding OEM ``` Then you can run the CLI tool. ``` webpack-bundle-analyzer bundle/output/path/stats.json ```

Options (for CLI)

```bash webpack-bundle-analyzer [bundleDir] [options] ``` Arguments are documented below: ### `bundleStatsFile` Path to webpack stats JSON file ### `bundleDir` Directory containing all generated bundles. ### `options` ``` /* Detailed source-code truncated for AI context efficiency. */ ```

Size definitions

webpack-bundle-analyzer reports three values for sizes. `defaultSizes` can be used to control which of these is shown by default. The different reported sizes are: ### `stat` This is the "input" size of your files, before any transformations like minification. It is called "stat size" because it's obtained from Webpack's [stats object](https://webpack.js.org/configuration/stats/). ### `parsed` This is the "output" size of your files. If you're using a Webpack plugin such as Uglify, then this value will reflect the minified size of your code. ### `gzip` This is the size of running the parsed bundles/modules through gzip compression. ### `brotli` This is the size of running the parsed bundles/modules through Brotli compression. ### `zstd` This is the size of running the parsed bundles/modules through Zstandard compression. (Node.js 22.15.0+ is required for this feature)

Selecting Which Chunks to Display

When opened, the report displays all of the Webpack chunks for your project. It's possible to filter to a more specific list of chunks by using the sidebar or the chunk context menu. ### Sidebar The Sidebar Menu can be opened by clicking the `>` button at the top left of the report. You can select or deselect chunks to display under the "Show chunks" heading there. ### Chunk Context Menu The Chunk Context Menu can be opened by right-clicking or `Ctrl`-clicking on a specific chunk in the report. It provides the following options: - **Hide chunk:** Hides the selected chunk - **Hide all other chunks:** Hides all chunks besides the selected one - **Show all chunks:** Un-hides any hidden chunks, returning the report to its initial, unfiltered view

Troubleshooting

### I don't see `gzip` or `parsed` sizes, it only shows `stat` size It happens when `webpack-bundle-analyzer` analyzes files that don't actually exist in your file system, for example when you work with `webpack-dev-server` that keeps all the files in RAM. If you use `webpack-bundle-analyzer` as a plugin you won't get any errors, however if you run it via CLI you get the error message in terminal: ``` Error parsing bundle asset "your_bundle_name.bundle.js": no such file No bundles were parsed. Analyzer will show only original module sizes from stats file. ``` To get more information about it you can read [issue #147](https://github.com/webpack/webpack-bundle-analyzer/issues/147). ### Cannot display report in Jenkins due to sandboxed iframe When viewing a static HTML report through Jenkins (for example with the HTML Publisher plugin), the page can appear blank. Jenkins serves HTML inside a sandboxed iframe that blocks scripts by default, and the report needs JavaScript to render. This is a Jenkins Content Security Policy restriction, not a bug in webpack-bundle-analyzer. To view the report you need to relax Jenkins CSP for Directory Browser Support. See [issue #168](https://github.com/webpack/webpack-bundle-analyzer/issues/168#issuecomment-381748354) for details and an example `hudson.model.DirectoryBrowserSupport.CSP` setting. ### `stats.json` has limited output If your generated `stats.json` contains limited information, check your Webpack configuration. Using `stats: 'error-only'` limits the information included in the generated stats file. Remove `stats: 'error-only'` or use a more detailed stats configuration when generating the stats file for `webpack-bundle-analyzer`.

Other tools

- [Statoscope](https://github.com/smelukov/statoscope/blob/master/packages/ui-webpack/README.md) - Webpack bundle analyzing tool to find out why a certain module was bundled (and more features, including interactive treemap)

Maintainers


Yuriy Grunin
Vesa Laakso
[npm]: https://img.shields.io/npm/v/webpack-bundle-analyzer.svg [npm-url]: https://npmjs.com/package/webpack-bundle-analyzer [node]: https://img.shields.io/node/v/webpack-bundle-analyzer.svg [node-url]: https://nodejs.org [tests]: https://github.com/webpack/webpack-bundle-analyzer/actions/workflows/main.yml/badge.svg [tests-url]: https://github.com/webpack/webpack-bundle-analyzer/actions/workflows/main.yml [downloads]: https://img.shields.io/npm/dt/webpack-bundle-analyzer.svg [downloads-url]: https://npmjs.com/package/webpack-bundle-analyzer

Contributing

Check out [CONTRIBUTING.md](./CONTRIBUTING.md) for instructions on contributing :tada: --- ### Overview (`.changeset/README.md`) # Changesets Hello and welcome! This folder has been automatically generated by `@changesets/cli`, a build tool that works with multi-package repos, or single-package repos to help you version and publish your code. You can find the full documentation for it [in our repository](https://github.com/changesets/changesets). We have a quick list of common questions to get you started engaging with this project in [our documentation](https://github.com/changesets/changesets/blob/main/docs/common-questions.md). --- ### Overview (`test/stats/with-module-in-multiple-assets/README.md`) # Fixture: one module in two assets This fixture tests one source module that Webpack puts in two output bundles. ## Test case The build has two entry files: - `src/long-message-entry.js` - `src/short-message-entry.js` Both files import `src/messages.js`. This is the source module that the two bundles share. `messages.js` exports a long message and a short message. Each entry file imports only one of these exports. Webpack creates these bundles: - `long-message.js` contains the long message. - `short-message.js` contains the short message. The configuration disables module concatenation, split chunks, and the separate runtime chunk. These settings keep the module visible in both bundles. ## Stats and bundle sizes Webpack gives `messages.js` module ID `906`. The stats report its source size as `87` in both chunks. Webpack removes the unused export from each bundle. This makes the emitted module factories different: - The factory in `long-message.js` has 59 characters. - The factory in `short-message.js` has 37 characters. The analyzer must report the correct factory size for each bundle. ## Rebuild Run this command from the repository root: ```sh npx webpack --config test/stats/with-module-in-multiple-assets/webpack.config.js ``` The `stats.json` file is a reduced copy of the Webpack stats. It contains only the fields that the analyzer reads. --- --- METRICS --- - Files Extracted: 3 - Estimated Token Budget: ~5074 tokens - Canonical Reference: https://codewiki.google/github.com/webpack/webpack-bundle-analyzer