JavaScript Beautifier

How to Use

Paste minified or inconsistently formatted JavaScript into the input box. The output updates live with consistent 2-space indentation, each statement on its own line, and each block clearly indented, making the logic easy to follow and debug. The default example loads a tiny single-line greet function with an if/else, beautify it and the braces expand into a K&R-style layout with each branch's return statement on its own indented line, a quick way to see the tool working before pasting in a real file.

What Beautification Changes, and What It Doesn't

Beautifying re-lays-out your code's whitespace, line breaks, and brace placement without touching a single token of actual logic. Variable names, function names, operators, string contents, and the order operations happen in are all preserved exactly. JavaScript's parser (and the JavaScript engine that runs it) treats most whitespace as insignificant between tokens, so if(name){return "Hi"} and the same code spread across three indented lines compile to the identical set of instructions. This is what makes beautifying completely safe to run on production code you're about to ship, or on a library you're studying, there is no risk of introducing a behavioral bug purely from reformatting.

Minified vs Obfuscated: Reading Someone Else's Code

It helps to separate two things that often get lumped together. Minified code (typically produced by a build tool like Terser or UglifyJS) is optimized purely for smaller file size: whitespace stripped, unnecessary semicolons removed, and often local variable names shortened to single letters, since a shorter name compresses to fewer bytes. Beautifying fully reverses the whitespace part of that and makes the logic readable again, though it cannot recover original variable names once they've been shortened, that information is gone the moment the minifier discards it. Obfuscated code goes a step further, deliberately restructuring control flow, encoding strings, or inserting dead code specifically to make the logic hard to follow even when nicely formatted, a technique sometimes used to protect intellectual property or, less legitimately, to hide malicious behavior. Beautifying obfuscated code will format it cleanly but won't undo the deliberate structural obfuscation itself, you'll get readable indentation around logic that's still intentionally convoluted.

JavaScript Formatting Conventions

This tool uses two-space indentation and places opening braces on the same line as the statement that introduces them (the "K&R" or "one true brace style" convention), matching the formatting most JavaScript style guides and linters (including widely used configs like Airbnb's and Standard's) default to. Each statement gets its own line rather than several chained together with semicolons, and each nested block, an if body, a function body, a loop body, indents one level deeper than its parent, making the code's structure visually obvious just from its shape, without needing to trace matching braces by eye.

Common Use Cases

Developers reach for a JavaScript beautifier most often when debugging in the browser, viewing a production site's loaded scripts in dev tools typically shows minified code, beautifying it makes it possible to set a breakpoint on a specific line and actually understand what's executing around it. It's equally useful for studying how a third-party library or open-source project implements something, pasting in a bundled distribution file and beautifying it turns an unreadable wall of code into something you can actually step through. Security researchers and curious developers alike use beautifiers as a first step when examining an unfamiliar script pulled from a webpage, since readable formatting is the first requirement for actually understanding what code does before deciding whether to trust it.

Common Mistakes and Limitations

Expecting beautified output to restore meaningful variable names is the most common misunderstanding, once a minifier renames a variable to a single letter, that original name is gone for good, no amount of reformatting can bring it back, only the code's author would know what it used to be called. Assuming beautifying makes obfuscated code fully readable is a related mistake, formatting and de-obfuscation are different problems, a script written specifically to resist analysis (control-flow flattening, string-array encoding, and similar techniques) stays hard to follow even with perfect indentation. Finally, treating beautified output as validated or safe to run without review is risky, this tool never checks whether your code is free of bugs or malicious behavior, it only reformats whatever you give it, reading the reformatted logic carefully is still up to you.

Frequently Asked Questions

Does this change how my JavaScript runs?

No, beautifying only adds indentation, line breaks, and consistent spacing, it doesn't change any variable name, logic, or operator. The reformatted code executes identically to the original, just laid out for human readability instead of minimal size.

Can this un-minify obfuscated code back to its original variable names?

No. Minifiers that rename variables to short names like a, b, c destroy the original names permanently, beautifying only restores formatting, not the lost information about what those variables were originally called.

Is it safe to paste code from an untrusted source into this tool?

Yes, safe in the sense that beautifying never executes your code, it only parses and reprints it as text, so pasting an unfamiliar script here will not run it or let it do anything to your browser or computer. That said, always be cautious about running unfamiliar JavaScript elsewhere, in a console or on a live page, after reading through it, beautifying is a reading aid, not a security scanner.

Does this tool run or execute my JavaScript?

No. The beautifier only parses your code's structure to reprint it with formatting, it never calls eval, never creates a script tag from your input, and never executes a single line of what you paste. You can safely beautify code without worrying about side effects like network requests or DOM changes firing.

Will it work on modern syntax like async/await, arrow functions, or classes?

Yes, the underlying js-beautify library understands standard modern JavaScript syntax, including arrow functions, async/await, template literals, destructuring, classes, and ES modules, formatting all of them with the same consistent indentation rules applied to older syntax. Extremely new or proposal-stage syntax not yet finalized in the language spec may not be supported.

Is my code sent to a server when I use this tool?

No. Beautification runs entirely in your browser using the open-source js-beautify library loaded from a CDN, and your input is never transmitted, logged, or stored anywhere. This makes it safe to beautify proprietary or unreleased code without it leaving your machine.