JavaScript Minifier

JS Full Form

JS is short for JavaScript - the programming language of the web browser. JS source files are written with generous indentation, comments, and line breaks that the JavaScript engine parses and then discards. Minification strips those tokens so your browser downloads and parses a smaller file, improving page load time.

What this tool does

• Strip comments - Removes // line comments and /* ... */ block comments (license blocks starting with /*! are preserved).
• Collapse whitespace - Removes indentation and redundant spaces, keeping one space only where two words, numbers or operators would otherwise merge, as in return x or a - -b. A line break is kept wherever removing it could change how the code runs.
• Respect strings - String literals, template literals, and regular expressions are left byte-for-byte identical. Code inside a template's ${...} is minified like any other code.
• Conservative by design - No identifier renaming (mangling), no scope hoisting, no dead-code elimination. Code runs the same after minifying, whether or not it uses semicolons.
• Byte savings - See original vs minified byte counts and percentage saved.

When you need a JS minifier

• Production deploys - Smaller .js bundles download and parse faster, improving Time to Interactive.
• Inline scripts - When embedding JS in HTML or email, every byte matters.
• Scripts in user content - When a CMS stores JS in a database row and you need it compact.
• Learning - Paste minified code and hit Beautify to see what a tool like Webpack actually ships to the browser.

How to use it

1. Paste a script into Input JavaScript, click Upload File to open a .js or .mjs file, or click Load Sample.
2. The minified code appears on the right as you type. Click Minify to refresh it.
3. Read the stats line to see the bytes saved.
4. Click Copy, or Download to save the result as minified.js.
5. Before you ship it, run the minified file once in the browser console or your test page to confirm it still works.

A worked example

This 167-byte snippet, written over several lines with two comments:

// Add GST to a price
function withGst(price, rate = 18) {
  /* rate is a percentage */
  return price + (price * rate) / 100;
}
console.log(`Total: ${withGst(500)}`);

becomes 102 bytes, about 39% smaller:

function withGst(price,rate=18){return price+(price*rate)/100;}
console.log(`Total: ${withGst(500)}`);

The space between return and price is kept because the two words would otherwise merge into one name, while the spaces around +, = and the brackets are removed. The text inside the template literal, including the space after the colon, is left exactly as written. The line break after the closing brace stays: a brace can end an object as well as a function, and in code without semicolons that line break is what ends the statement. It costs one byte, the same as a space.

Code without semicolons

JavaScript lets you leave semicolons out and relies on line breaks instead. The minifier follows the same rules, so it only removes a line break when the statement clearly carries on, for example when the line ends with a comma, an operator or an opening bracket, or the next line starts with a dot, a closing bracket or an operator:

• let a = 1 on one line and let b = 2 on the next stay on separate lines as let a=1 and let b=2.
• a - -b becomes a- -b and a + +b becomes a+ +b, so they never turn into the -- and ++ operators.
• A bare return with its value on the next line keeps its line break, so it still returns undefined. The same goes for break, continue, throw, and a line that starts with ++ or --.
• A regular expression after return, typeof, an if (...) condition or inside ${...} is recognised as one, so its spaces are kept.

For production bundles a parser-based tool such as Terser or esbuild will still give smaller output, because it also renames variables and removes code that never runs.

Privacy

Everything runs locally in your browser. Your JavaScript is never sent to our servers, not even for analytics. You can minify proprietary business logic, unreleased features, or internal tooling without anything leaving your machine.