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JS Minifier

Minify JavaScript quickly in browser.

How This Tool Works

The JavaScript Minifier removes whitespace, comments, and shortens variable names in JavaScript code to reduce file size for production deployment. Large JavaScript files are a primary cause of slow page load times, particularly on mobile devices. Minification can reduce JS file size by 40–70%. The minified output is functionally identical — variable renaming is done in a way that preserves all behavior. Keep original source files for editing and debugging.

How to Use

  1. Paste your JavaScript in field A.
  2. Click Run. The minified JavaScript is returned.
  3. Save the output as filename.min.js for use in your production HTML.
  4. Always keep the original .js file — you cannot recover readable code from minified output.

Common Questions

What is the difference between minification and uglification?

Minification removes whitespace and comments. Uglification (uglifyJS) also renames variables to single letters (a, b, c) to further reduce size. Both produce functionally identical code. Modern bundlers like webpack and esbuild do both automatically.

Do I need to manually minify JS if I use webpack or Vite?

No. Build tools like webpack, Vite, Rollup, and Parcel minify JavaScript automatically in production mode. Manual minification is only needed for standalone scripts not going through a build pipeline.

What are source maps?

Source maps are separate files (.map) that map minified code back to the original source. Browser DevTools use them to show readable code during debugging while the browser actually runs minified code.