JavaScript Minifier: Compress JS and Reduce File Size Online
Compress JavaScript by removing comments and whitespace, and optionally renaming local variables to short names. Shows the bytes saved. Runs in your browser.
Paste your JavaScript and press Minify. Comments and extra whitespace are removed, and the page shows the size before and after. Tick Rename local variables to shorten function parameters and variables too. The renamer is careful: it leaves global names, object properties and anything it cannot prove safe alone.
What it does
- Removes comments and extra spaces and line breaks.
- Keeps line breaks only where the language needs them, so the code behaves the same.
- Leaves strings, template literals and regular expressions untouched.
- Optional: renames variables, parameters and inner functions inside functions to short names, using real scope analysis.
- Never renames top-level names, object properties or anything used with eval or with.
The renamer changes the names of local variables, so function.name values inside functions and stack traces will show short names. Test your code after minifying, as with any minifier. It does not remove dead code or rewrite expressions like Terser does.
Example
Before
// add two numbers
function add(a,b){const total=a+b;if(total>10){console.log("big")}return total}
const items=[1,2,3].map(n=>add(n,2));After
function add(a,b){const total=a+b;if(total>10){console.log("big")}return total}
const items=[1,2,3].map(n=>add(n,2));Frequently asked questions
- Is this as small as Terser or esbuild?
- Not quite. With renaming on, local names shrink like in those tools, but it does not remove dead code, inline functions or rewrite expressions. For production builds, use a build tool; for quick jobs and snippets this gets most of the saving.
- What does Rename local variables change?
- Only names that live inside functions: parameters, var, let, const, inner functions and classes. Names at the top level of your script stay as they are, because other scripts and your HTML may use them. Property names (obj.name) are never changed.
- When does it skip renaming?
- If the code calls eval(), uses a with statement, contains JSX, TypeScript or type annotations, or has a syntax error, the page tells you why and still removes comments and whitespace.
- Will it break my code?
- The renamer is checked by running real programs before and after renaming and comparing the results. Even so, test minified code. Code that depends on function names or reads its own source with toString() can behave differently.
- Can it handle modern JavaScript?
- Yes: arrow functions, classes, destructuring, template literals, optional chaining, generators and async code.
- Does it keep license comments?
- Tick the option to keep comments that start with /*!
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