JavaScript Minifier

What is a JavaScript minifier?

JavaScript minification shrinks a script by removing comments and unnecessary whitespace while keeping the program's behavior identical. This minifier is deliberately conservative: instead of renaming variables or restructuring code like production tools do, it runs a small state machine over the source that understands strings, template literals, regular expressions, and comments. That means a // inside a string is never mistaken for a comment, and a / starting a regex is never mistaken for division. The result is smaller, safe-to-test output — with a clear warning that production builds deserve Terser or esbuild.

How to use this tool

1. Paste your JavaScript into the input box.
2. Press Minify — comments are stripped and whitespace is collapsed wherever the state machine proves it safe.
3. Check the size-savings card, then copy the output or download it as a .js file.
4. Test the minified script in a browser or with node before deploying it anywhere.

Key features

• State-machine parser distinguishing code, line/block comments, single/double-quoted strings, template literals (including nested ${}), and regex literals.
• Smart regex-vs-division detection using the previous significant token and keyword context (return, typeof, and friends).
• ASI protection: newlines are preserved where joining lines could change semantics, such as after return or throw.
• Keeps required spaces (between identifiers, around ++/-- sequences) and drops everything else.
• Shebang lines (#!/usr/bin/env node) are preserved for CLI scripts.
• Size-savings report with copy and download, all processed locally in your browser.

Common use cases

• Quick size wins: shrinking a standalone script before embedding it in a page.
• Bookmarklets: compressing code that must fit in a bookmark URL.
• Email-safe scripts: reducing payload size for constrained environments.
• Learning: watching what a minifier actually changes (and does not change) in real code.
• Prototyping: a no-install minification step before setting up a proper build pipeline.

Practical tips

• Always run the minified output through your test suite or at least smoke-test it — minifiers can surprise you on edge-case syntax.
• This tool does not rename variables or remove dead code; for real production savings, use Terser, esbuild, or swc.
• Keep source maps in mind: debugging minified code without a map is painful, so generate maps in your build tool.
• Minification and gzip/Brotli stack — the smaller the input, the better compression works.
• If output behaves differently, the usual suspects are missing semicolons in the source or exotic syntax the simple state machine mishandles — file a note and use a full parser instead.