Bundlephobia is an online tool that helps developers evaluate the cost of adding JavaScript (npm) packages to their applications. It provides key metrics such as bundle size, gzipped size, dependency size, and estimated download time.

The tool addresses performance issues caused by large or inefficient dependencies by giving clear insights into how each package affects bundle size. It analyzes package contents and dependencies to estimate their impact on production builds, helping developers choose lighter and more efficient libraries.

Bundlephobia is commonly used in frontend development workflows to compare packages and maintain fast-loading web applications.

Key features include:

• Bundle size analysis (minified and gzipped)
• Estimated download time for packages
• Dependency tree and package composition insights
• Search for any npm package
• Support for comparing package impact

Common use cases include evaluating npm packages before installation, optimizing frontend performance, comparing alternative libraries, reducing bundle size in web apps, and monitoring dependency impact in JavaScript projects.