liminfoJS Minifier
Free web tool: JS Minifier
About JS Minifier
The JavaScript Minifier is a free, browser-based tool that reduces the size of your JavaScript source code by stripping single-line comments (//) and block comments (/* */), removing leading and trailing whitespace on each line, eliminating blank lines, collapsing spaces around operators and punctuation, and finally joining all lines into a single compact output. The result is a minified script that is functionally identical to the original but significantly smaller in byte size.
This tool is used by front-end developers, web performance engineers, and students who need to quickly reduce JS payload size for production builds, understand what minification does under the hood, or test whether a minified snippet produces expected output. Because all processing happens entirely inside your browser using pure JavaScript string operations and regular expressions, no code is ever transmitted to a server, making the tool completely private and instant.
The live size comparison panel shows the original byte count, the minified byte count, and the percentage saved after each minification run. This makes it easy to benchmark different approaches to writing JavaScript and understand which patterns — such as long variable names versus short ones, or heavy commenting — have the greatest impact on file size.
Key Features
- Removes single-line (//) and block (/* */) comments in one pass
- Strips leading and trailing whitespace from every line
- Collapses spaces around operators, braces, semicolons, and commas
- Joins all lines into a single-line minified output string
- Displays original vs minified byte counts with percentage saved
- One-click copy of the minified output to clipboard
- 100% client-side — source code never leaves your browser
- Dark mode support and responsive layout for any screen size
Frequently Asked Questions
What does JavaScript minification actually do?
Minification removes content that is only needed by humans reading the code — comments, extra spaces, and blank lines — while keeping all the tokens the JavaScript engine needs to execute it. The resulting file is byte-for-byte functionally equivalent but much smaller, which reduces download time and speeds up page load.
How much size reduction can I expect?
Typical hand-written JavaScript with comments reduces by 30–60%. Heavily commented tutorial code can see reductions above 70%. The tool shows the exact percentage after each run so you can compare different inputs.
Does the minifier rename variables or mangle identifiers?
No. This tool performs whitespace and comment removal only — it does not rename local variables, mangle identifiers, or apply dead-code elimination. For full uglification with variable mangling, tools like Terser or UglifyJS are more appropriate for production pipelines.
Is this safe to use on production code?
This tool is designed for quick checks and learning. For production deployments, integrate a battle-tested tool like Terser into your build pipeline. That said, the output of this minifier is valid JavaScript — it removes only comments and whitespace, nothing that affects execution.
Can I minify TypeScript or JSX with this tool?
The tool operates as a text-level processor, so TypeScript syntax and JSX will not cause errors, but TypeScript type annotations and JSX tags will remain in the output. For proper TS/JSX minification you need a transpiler like tsc or Babel first.
Why are my regex literals breaking after minification?
Regex literals that follow division operators can be ambiguous for simple text-based minifiers. If you encounter issues, wrap your regex in a RegExp constructor call instead of a literal, or test the minified output in the browser console before deploying.
Is my source code sent to any server?
No. All processing runs entirely in your browser using JavaScript string methods and regular expressions. No code is uploaded, logged, or stored anywhere.
Can I minify multiple files at once?
Currently the tool processes a single text input at a time. For batch minification of multiple files, you can paste concatenated scripts into the input or use a build tool like Webpack, Rollup, or esbuild in your project.