bundle-autopsy

Your bundle is bloated. This tells you exactly why.

npx bundle-autopsy dist/

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The problem

You opened webpack-bundle-analyzer. It's a colorful treemap. Cool.

You stare at it for five minutes, squinting at rectangles. You now know moment is big. You knew that already.

bundle-autopsy tells you EXACTLY what to replace and how much you'll save.

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Sample output

  BUNDLE-AUTOPSY  v1.0.0

  Analyzing 3 files
  Total bundle: 847.0 KB  (3 files, ~12 modules detected)

  -- Top Offenders ------------------------------------

  # 1  moment + moment-timezone    254 KB  (30.0%)  ##############..
  # 2  lodash                       72 KB  ( 8.5%)  #####...........
  # 3  validator                    60 KB  ( 7.1%)  ####............
  # 4  react-dom                    42 KB  ( 5.0%)  ###.............
  # 5  axios                        13 KB  ( 1.5%)  #...............

  -- Lighter Alternatives -----------------------------

  moment (67KB)            -> date-fns (13KB)               save 54 KB
  moment-timezone (187KB)  -> Intl.DateTimeFormat            save 187 KB
  lodash (72KB)            -> lodash-es (tree-shake)         save ~67 KB
  validator (60KB)         -> zod + native                   save 50 KB
  axios (13KB)             -> native fetch                   save 13 KB

  -- Potential Savings --------------------------------

  Current:          847.0 KB
  After swaps:      476.0 KB
  Potential savings: 371.0 KB (43.8% of bundle)

  -- Tree-Shake Opportunities -------------------------

  > import lodash from 'lodash' -> import { ... } from 'lodash-es'
  > import * as utils from './utils' -- import only what you need

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Install

# Run without installing (recommended)
npx bundle-autopsy dist/

# Install globally
npm install -g bundle-autopsy

# Install as dev dependency
npm install -D bundle-autopsy

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Commands

Command	Description
bundle-autopsy dist/	Analyze all JS files in a directory
bundle-autopsy bundle.js	Analyze a specific file
bundle-autopsy . --sourcemap	Use source maps for precise module-level analysis
bundle-autopsy . --budget 200	Set size budget in KB, exit 1 if exceeded
bundle-autopsy . --json	JSON output (for CI pipelines and scripting)
bundle-autopsy . --top 20	Show top 20 offenders (default: 10)

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CI usage with --budget

Fail your build when the bundle gets too big:

# GitHub Actions
- name: Bundle size check
  run: npx bundle-autopsy dist/ --budget 500 --json

# package.json scripts
"scripts": {
  "build:check": "vite build && bundle-autopsy dist/ --budget 300"
}

Exit codes:

• 0 — Analysis complete, budget OK (or no budget set)
• 1 — Budget exceeded, or fatal error

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Source map analysis

For precise, byte-accurate module sizes, build with source maps enabled and use --sourcemap:

Vite:

// vite.config.js
export default { build: { sourcemap: true } }

webpack:

// webpack.config.js
module.exports = { devtool: 'source-map' }

Rollup:

// rollup.config.js
export default { output: { sourcemap: true } }

Then run:

bundle-autopsy dist/ --sourcemap

Without source maps, autopsy uses heuristics — still useful, just less precise.

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Alternatives database

40+ packages covered. A sample:

Package	Size	Alternative	Alt Size	Savings
moment	67KB	date-fns	13KB	54KB
moment-timezone	187KB	Intl.DateTimeFormat	0KB	187KB
lodash	72KB	lodash-es (tree-shake)	~5KB	67KB
axios	13KB	native fetch	0KB	13KB
validator	60KB	zod + native	~10KB	50KB
joi	142KB	zod	~10KB	132KB
jquery	87KB	native DOM APIs	0KB	87KB
uuid	12KB	crypto.randomUUID()	0KB	12KB
bluebird	30KB	native Promise	0KB	30KB
core-js	500KB	targeted polyfills	~20KB	480KB
highlight.js	1100KB	selective languages	~20KB	1080KB
request	49KB	native fetch/undici	0KB	49KB
chalk	12KB	picocolors	1KB	11KB
immutable	57KB	immer	~13KB	44KB
crypto-js	51KB	Web Crypto API	0KB	51KB

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Why not webpack-bundle-analyzer?

webpack-bundle-analyzer shows you the problem.

bundle-autopsy gives you the fix.

Feature	webpack-bundle-analyzer	bundle-autopsy
Visualizes module sizes	Yes (treemap)	Yes (terminal bar chart)
Suggests replacements	No	Yes, with savings estimates
Tree-shake opportunities	No	Yes
CI-friendly with exit codes	No	Yes (--budget)
JSON output for scripting	No	Yes (--json)
Works without config	No (webpack only)	Yes, any bundler
Requires a browser	Yes	No

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Supported bundlers

Works with output from any bundler that produces standard JS:

• webpack (module IDs, CONCATENATED MODULE comments)
• vite (ES module output, rollup-based)
• rollup (module markers, import paths)
• esbuild (chunk comments, module paths)
• parcel (node_modules references)

For best results with any bundler, enable source maps and use --sourcemap.

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License

MIT - Nicholas Ashkar, 2026