Look before you leap. Inspect the minified & gzipped cost of any npm dependency before you install it.

npm install <package> is a one-way door. By the time you've installed the package, wired it up, built the app, and fired up a bundle visualizer, you've already committed to the bloat. weight-check flips that around: it pings the Bundlephobia API and prints a clean, colorized cost report in your terminal — no install, no build, no visualizer required.

npx weight-check lodash

  lodash@4.17.21  ● Moderate
  Lodash modular utilities.

  Minified        68.5 KB
  Minified + gzip 24.7 KB

  Download time (gzipped)
    Slow 3G       493 ms
    Emerging 4G   28 ms

  Dependencies    0
  Tree-shakeable  no ESM build
  Side effects    declared

• Instant size reports — minified and minified + gzipped sizes for any package.
• Version-pinned checks — weight-check react@18.2.0 measures the exact version you care about.
• Multi-package mode — pass several packages and get a compact comparison table plus a grand total.
• compare — put alternatives head-to-head (moment vs dayjs vs date-fns), sorted lightest-first with a winner and % savings.
• scan — audit an entire project's package.json and see your total install weight, ranked by size, with heavy packages flagged.
• scan --recursive — point it at a folder and audit every project underneath it at once (monorepos included), with a per-project ranking, the heaviest packages across everything, and your total vs. unique dependency footprint.
• CI budgets — --max-size 50kb exits with code 1 when a package blows your budget, so you can fail a build on bloat.
• Download-time estimates — see how long each bundle takes on Slow 3G and Emerging 4G.
• Tree-shaking signals — whether the package ships an ESM build and declares side effects.
• --json — machine-readable output for scripts and dashboards.
• Local caching — pinned versions never change, so repeat runs are instant (7-day TTL by default).
• Zero footprint — it never installs anything into your project.

Run it on demand without installing:

npx weight-check lodash

Or install globally for the shortest possible feedback loop:

npm install -g weight-check
weight-check lodash      # or the shorthand: wcheck lodash

Requires Node.js 18+ (uses the built-in fetch).

weight-check lodash
weight-check react@18.2.0
weight-check react react-dom axios          # comparison table + total

weight-check compare moment dayjs date-fns
# alias:
weight-check vs moment dayjs date-fns

┌───┬──────────┬──────────┬─────────────┬────────────────────┬─────────┐
│   │ Package  │ Min+Gzip │ vs lightest │ Relative           │ Slow 3G │
├───┼──────────┼──────────┼─────────────┼────────────────────┼─────────┤
│ ★ │ dayjs    │   3.0 KB │    baseline │ █░░░░░░░░░░░░░░░░░ │   59 ms │
│   │ date-fns │  17.1 KB │    +14.1 KB │ ████░░░░░░░░░░░░░░ │  342 ms │
│   │ moment   │  75.4 KB │    +72.4 KB │ ██████████████████ │  1.51 s │
└───┴──────────┴──────────┴─────────────┴────────────────────┴─────────┘

  ★ dayjs is the lightest — 72.4 KB (96%) smaller than moment.

weight-check scan                 # runtime dependencies in ./package.json
weight-check scan --dev           # include devDependencies
weight-check scan --dev-only      # only devDependencies
weight-check scan --project ../my-app
weight-check scan --top 20        # only the first 20 dependencies

Point scan --recursive (-r) at a parent folder and weight-check discovers every project beneath it (skipping node_modules, dist, etc.), measures each package once, and reports the big picture:

weight-check scan -r                       # every project under the current folder
weight-check scan -r -p ~/Projects         # every project under ~/Projects
weight-check scan -r --depth 3 --dev       # go 3 levels deep, include devDependencies

  weight-check scan --recursive  /Users/me/Projects
  10 projects · 28 unique packages

┌────────────────────┬──────┬──────────┬────────────────────┐
│ Project            │ Deps │   Weight │ Share              │
├────────────────────┼──────┼──────────┼────────────────────┤
│ @arch-atlas/core   │    5 │   1.6 MB │ ██████████████████ │
│ @arch-atlas/web    │    4 │ 525.8 KB │ ██████░░░░░░░░░░░░ │
│ …                  │      │          │                    │
└────────────────────┴──────┴──────────┴────────────────────┘

  Heaviest packages (across all projects)
  ts-morph 1.3 MB · lucide-react 421.5 KB · @babel/traverse 190.0 KB · …

  Combined weight    3.0 MB gzipped (counting shared deps once per project)
  Unique footprint   2.4 MB gzipped (22 distinct packages)
  Most shared        chalk — used in 4 projects

• Combined weight sums each project's total (a shared dep is counted once per project that uses it).
• Unique footprint counts every distinct package exactly once — your true dependency surface area.

weight-check axios --max-size 20kb            # exit 1 if axios > 20 KB gzipped
weight-check scan --max-size 50kb             # fail if ANY dependency > 50 KB

The process exits with code 1 when a budget is exceeded (or a package can't be measured), so it drops straight into a CI pipeline:

# .github/workflows/bundle-budget.yml
- run: npx weight-check scan --max-size 75kb

weight-check react --json
weight-check scan --json > bundle-report.json

These flags work on check (default), compare, and scan:

scan-specific flags:

Cache management:

weight-check cache path      # print the cache file location
weight-check cache clear     # remove all cached sizes

• Minified + gzip is the number that actually travels over the wire — it's what weight-check colors and ranks by.

• Verdicts are opinionated thresholds on the gzipped size:

  Verdict	Gzipped size
  ● Featherweight	≤ 5 KB
  ● Light	≤ 20 KB
  ● Moderate	≤ 50 KB
  ● Heavy	≤ 100 KB
  ● Massive	> 100 KB

• Download times use effective throughput of ~50 KB/s (Slow 3G) and ~875 KB/s (Emerging 4G), matching Bundlephobia's own profiles.

• Two size sources. Web-friendly packages get true bundle sizes from Bundlephobia (minified + gzip). React Native, Expo, native modules, and @types/* packages can't be browser-bundled, so weight-check automatically falls back to npm install size (unpacked on disk + published tarball). Rows are labelled bundle or install so you always know which you're looking at.
• Use --bundle-only if you want to skip the fallback and only accept Bundlephobia numbers.
• Version ranges in package.json (^1.2.3) are pinned to their base version (1.2.3) when scanning; non-semver specs (workspace:*, git URLs, latest) fall back to the latest published version.
• Bundle sizes reflect the package on its own — real-world impact depends on your bundler, tree-shaking, and code you actually import. Install sizes are a different (still useful) signal: how heavy the dependency is to download and unpack.

MIT © phemymii