Is the JS minifier free?

Yes, completely free with no signup required.

Where does the minification happen — is my source code sent to a server?

Nowhere but your own machine. Terser runs fully in your browser; the code you paste is never transmitted.

How is JS minification different from CSS minification?

It goes much further. Beyond stripping whitespace and comments, Terser renames local variables to single letters, removes dead code, and collapses expressions — which is why JavaScript compresses 30–60% versus 20–40% for CSS.

Will minified code behave identically to the original?

For standard JavaScript, yes — Terser is the same minifier Webpack and Vite use in production. The known exceptions are code that inspects function.name or parses its own stack traces, since identifiers are renamed.

Can I undo minification?

Beautify mode restores indentation and line breaks for readability, but original variable names cannot be recovered — renaming is one-way. Keep your source files; treat minified output as a build artifact.

Dev Tools

JavaScript Minifier & Beautifier Online Free

Minify JavaScript using Terser or beautify with js-beautify. Shows compression ratio. Browser-based.

Files never storedInstantNo signup

🔒 Your file never leaves your browser. All processing runs locally using Terser.

Input JavaScript

Output

How to Minify JavaScript Online

1
Paste your JavaScript
Paste your JavaScript code in the input box.
2
Click Minify or Beautify
Minify compresses using Terser. Beautify formats the code with consistent indentation.
3
Copy the result
Click Copy to copy the processed code to your clipboard.

JavaScript is usually the heaviest part of a page — not just to download but to parse and execute. Unlike CSS minification, which only strips whitespace, a real JavaScript minifier rewrites your code: local variables become single letters, dead branches are eliminated, and expressions are collapsed into shorter equivalent forms. That is why JS routinely compresses 30–60%, far more than markup or styles.

Powered by Terser: this tool runs Terser — the same minifier used internally by Webpack, Vite, and Rollup — compiled to run entirely in your browser. You get production-grade output without installing Node or configuring a bundler, which is handy for one-off scripts, code you paste into a CMS, or quick size checks.

What stays safe: exported names, string contents, and anything reachable from outside the file are never renamed. The edge cases to know about: code that reads function.name at runtime, or stack-trace parsing, can behave differently after mangling — keep a source map or an unminified copy for debugging.

Beautify mode reverses the process for readability: paste minified vendor code and get consistent indentation back (though original variable names are gone for good — renaming is one-way). Pair this with the CSS minifier and JSON formatter when you are slimming down a whole deployment.

Frequently Asked Questions

Related Dev Tools

CSS Minifier HTML Minifier JSON Formatter