JavaScript Beautifier

About this tool

JavaScript pulled from a production bundle, a browser's dev tools source view, or a minifier's output is often nearly unreadable — variable names shortened to single letters, no line breaks between statements, semicolons doing all the structural work that indentation and whitespace normally would. That's the entire point of minification from a tooling perspective (smaller files, faster downloads), but it makes the code useless as something a human can read and reason about without reformatting it first.

Beautifying reconstructs readable structure by tracking brace and bracket nesting — every { opens a new indentation level, every matching } closes it — and inserting line breaks at statement boundaries (semicolons) and block boundaries, so a function body, an if/else chain, or a nested callback shows its actual shape instead of running together as one dense line. This is the single most useful thing you can do to a piece of minified code before trying to understand what it does: structure alone, without changing a single variable name, makes a huge difference in readability.

Minifying reverses that: it strips comments, collapses unnecessary whitespace, and removes line breaks that exist purely for human readability, since none of that affects how the JavaScript engine parses or executes the code. This tool's minifier is deliberately conservative — it removes whitespace and comments without attempting more aggressive optimizations like variable renaming or dead-code elimination, which real production minifiers (Terser, esbuild, SWC) do but which require a full understanding of the code's semantics to do safely. A conservative minifier that only touches whitespace is guaranteed not to change behavior; an aggressive one can, if it gets an edge case wrong, which is why production builds should still go through a proper bundler's minifier rather than relying on this tool for a shipped build.

The syntax highlighting in the output — keywords, strings, numbers, comments, and function names each colored distinctly — exists to make the reformatted code easier to scan visually, the same benefit a code editor's highlighting gives you, applied directly to the beautified result. This tool works from JavaScript's lexical structure (matching braces, strings, comments, and keywords) rather than a full AST-based parse, which means it handles the vast majority of real-world code correctly but, like any lightweight beautifier, can occasionally misjudge unusual edge cases — a regex literal that looks like a division operator, for instance. Everything runs locally in your browser; nothing you paste is sent anywhere.