Typically 30–70%, depending on the source. Heavy indentation, many comments, and long descriptive variable names compress the most, while already-compact code sees less. As real-world examples, a large library can drop by around 70% and a typical ES6 app by roughly 50%. The tool shows the exact percentage in real time.

Done correctly, no. Safe minification only removes unnecessary characters and renames local variables, leaving global names, function names, property keys, strings, and runtime behavior intact. The edge cases are dynamic patterns like eval(), with, and global access via window['name'], which can break — so test minified output on staging before production when your app uses dynamic evaluation.

Yes. It handles ES6 through ES2024 — arrow functions, classes, modules, async/await, optional chaining, nullish coalescing, template literals, destructuring, and private class fields — and preserves JSX, TypeScript, and Flow syntax, with partial Vue template support. Note it formats and minifies rather than transpiles, so pair it with Babel if you need JSX or TS compiled down.

A source map is a .map file that links minified code back to your original source, so browser devtools show real file names, line numbers, and stack traces and let you set breakpoints on readable lines. Without one, debugging minified production code is nearly impossible. Generate maps when minifying, and deploy them to staging or to production when you need live debugging