JS Minifier

How to use it

1. Paste JavaScript or drop a .js file up to 5 MB — small scripts minify as you type, larger ones on a background thread.
2. Toggle Compress, Mangle and Keep /*! license comments; each change re-runs the current script.
3. Read the report card — original, minified and gzip bytes, and percentage saved — or a plain already-minified line.
4. Copy the output, download a .js file, or share a link that carries only your code and options.

Paste a script and the minified version appears as you type, beside a report card that names the numbers a bundle cares about: original bytes, minified bytes, gzip weight and percentage saved. Terser does the work — renaming locals, folding constants and dropping dead code — while /*! license banners stay by default, and nothing you paste is uploaded.

Examples

function formatMoney(amount, currency) {
  const symbols = { USD: "$", EUR: "€", GBP: "£" };
  const symbol = symbols[currency] || currency;
  return symbol + amount.toFixed(2);
}

function applyDiscount(price, percent) {
  const saved = price * (percent / 100);
  return formatMoney(price - saved, "USD");
}

function formatMoney(n,o){return({USD:"$",EUR:"€",GBP:"£"}[o]||o)+n.toFixed(2)}function applyDiscount(n,o){return formatMoney(n-n*(o/100),"USD")}

/*! shim v2.1.0 | (c) 2026 Example Inc | MIT */
function polyfillClosest(el, selector) {
  while (el) {
    if (el.matches(selector)) return el;
    el = el.parentElement;
  }
  return null;
}

/*! shim v2.1.0 | (c) 2026 Example Inc | MIT */
function polyfillClosest(e,l){for(;e;){if(e.matches(l))return e;e=e.parentElement}return null}

function isEven(n){return n%2==0}

function isEven(n){return n%2==0}

function greet(name) {
  return "Hello, + name;
}

JavaScript could not be parsed: Unterminated string constant (line 2, column 10).

Every example on this page is executed against the same engine that powers the tool, on every build.

Common errors

JavaScript could not be parsed: Unexpected token: punc (}) (line 4, column 1).

A property access with nothing after the dot leaves the parser expecting a name; the closing brace is where it gives up. Jump to error lands on the position Terser reports, in Terser's own words.

This tool minifies up to 5MB of JavaScript; beyond that, try the CLI: npx terser input.js --compress --mangle --output output.min.js

Rather than minify part of an oversized paste, the page declines it and leaves your code in the editor. The command runs the same Terser on your machine, with nothing uploaded.

JavaScript minification failed: RangeError: Maximum call stack size exceeded

The catch-all for when Terser throws instead of reporting a parse position — reproduced with hundreds of thousands of nested parentheses. Nothing is emitted; the input is untouched.

Keyboard shortcuts

⌘/Ctrl + Enter

Re-run the minifier on the current script.

⌘/Ctrl + S

Save output as a .js file — this overrides the browser's save-page shortcut.

⌘/Ctrl + C

Copy the whole output when nothing is selected; a real selection copies itself.

⌘/Ctrl + Shift + C

Force a copy of the whole output, selection or not.

t

Toggle the color theme — idle while typing or composing with an IME.

? or ⌘/Ctrl + /

Open help — the dialog lists every binding and where a browser might grab it.

Esc

Close the top dialog; it never clears your input.