ToolsGuru

Bundlephobia Analyzer

Check npm package sizes before installation to optimize your bundle

Package Analysis

Check the size and cost of any NPM package

Inspect the gzipped, minified and parsed size of any NPM package before adding it to your project. See dependency counts, tree‑shaking compatibility and download time over fast and slow networks — so you can avoid the dreaded 200 KB utility that quietly tanks your bundle.

JavaScript bundle size is one of the biggest performance levers on the modern web. Adding the wrong dependency can blow your performance budget, hurt Core Web Vitals, and degrade conversion. Inspecting size before installation is one of the highest‑leverage habits a frontend engineer can build.

Powered by the bundlephobia API and presented in a clean, side‑by‑side interface, this tool also lets you compare alternatives — for example, lodash vs lodash‑es vs ramda — so you pick the smallest viable option for your use case.

Why use Bundlephobia Viewer?

Real bundle metrics

Minified, gzipped and parsed sizes for any version of any package.

Compare alternatives

Stack two or more packages side‑by‑side to choose the smallest.

Tree‑shake aware

See whether a package is tree‑shake friendly so you only ship what you use.

Fast and free

No signup, no rate limits beyond the upstream API.

How to use Bundlephobia Viewer

  1. 1

    Type a package name

    Search any package available on the public NPM registry.

  2. 2

    Pick a version

    Inspect the latest release or any specific version.

  3. 3

    Review the metrics

    Compare gzipped, minified and parsed sizes plus download times.

  4. 4

    Compare alternatives

    Add competing packages to a comparison view to pick the lightest.

Common use cases

Pre‑install vetting

Check size before npm install to protect your bundle budget.

Migration planning

Compare moonjs vs dayjs vs date‑fns before swapping date libraries.

Performance audits

Identify oversized packages already in your bundle and find lighter replacements.

Education

Show junior engineers the real cost of casual dependency choices.

Features at a glance

Frequently asked questions

How do I check the size of an npm package?

Enter the npm package name (e.g., react, lodash) in our Bundlephobia Analyzer. It shows the minified size, gzipped size, and estimated download time.

What is the difference between minified and gzipped size?

Minified size is the package after whitespace and comments are removed. Gzipped size is what's actually downloaded over the network, which is typically 70% smaller.

Can I check if an npm package supports tree-shaking?

Yes. Our analyzer indicates whether a package has side-effect-free modules enabling tree-shaking, which means only the code you use is bundled.

Why should I check npm package sizes before installing?

Large packages significantly increase your JavaScript bundle size, slowing down page loads. Checking sizes upfront helps you choose lighter alternatives.

Your privacy matters

Bundlephobia Viewer runs entirely in your web browser. Your files, text, and data are never uploaded to any server, never stored, and never seen by us or any third party. This client-side architecture means you can safely process confidential business documents, personal records, and proprietary data without privacy concerns.

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