JavaScript Beautifier / Formatter
Format and beautify minified JavaScript into clean, readable code with proper indentation.
Paste minified JavaScript and click Beautify to format it with proper indentation, line breaks, and spacing. Formatting runs in your browser after the page loads.
Use it to make compressed JavaScript readable enough to inspect structure, blocks, and statements.
Why Beautify JavaScript?
Minified JavaScript is designed for machines, not humans. Variable names compressed to single letters, all whitespace stripped, entire libraries on a single line, it's fast to download but impossible to debug. A JS beautifier reverses this process, adding indentation and line breaks so you can actually read the code.
You'll reach for a beautifier when debugging production issues (reading minified error stack traces), reviewing third-party scripts (what does that analytics snippet actually do?), or reformatting code that someone pasted without indentation. It's a development tool you use more often than you'd expect.
This tool handles common JavaScript patterns including strings, objects, arrays, and nested blocks. For parser-aware formatting with full syntax understanding, use a project formatter such as Prettier. For quick reformatting of minified code, this gives you a readable first pass.
JavaScript Formatting Conventions
| Convention | Standard | Why It Matters |
|---|---|---|
| Indentation | 2 spaces (most JS projects) | Keeps deeply nested callbacks and promises readable |
| Semicolons | Required (Standard JS) or omitted (no-semi) | Team preference, be consistent, ASI can cause bugs |
| Quotes | Single quotes (Airbnb) or double (Standard) | Pick one, enforce with a linter, never mix |
| Braces | Same-line opening brace (K&R style) | Nearly universal in JS, Allman style is rare |
| Line length | 80-120 characters | Prevents horizontal scrolling in code review |
| Trailing commas | Required in many current configs | Cleaner git diffs, adding an item doesn't touch the previous line |
What this means for you: Formatting conventions are about consistency, not correctness. The specific choices matter less than everyone on the team following the same rules. Use ESLint + Prettier in your project for automated enforcement.
When to Use Different Formatting Tools
This online beautifier
Quick one-off formatting of minified code, third-party scripts, or code snippets from Stack Overflow. No installation or project configuration needed. Useful for reading code, not for enforcing style in a project.
Prettier
The industry standard for automated JS/TS formatting. Opinionated (few config options by design), AST-based (understands code structure), integrates with editors and CI. Use this in your actual project.
ESLint --fix
Fixes formatting AND code quality issues. Catches unused variables, missing error handling, and style violations. ESLint + Prettier together give you formatting + linting in one pass.
Browser DevTools
Chrome DevTools has a built-in "Pretty print" button ({}) in the Sources panel. Click it to format any minified script loaded on the page. Great for debugging production issues in real time.
Worked Example: Reading a Minified Error Stack
A production error points Marcus to app.min.js:1:48291. There is no source map available, so he copies the nearby minified function into a formatter.
1. Restore block shape
Indentation reveals a try/catch block, a fetch call, and a JSON parse step. The variable names are still short, but the control flow is visible.
2. Find the failing branch
The readable version shows an early return when response.okis false. The minified one-line version hid that branch.
3. Confirm with DevTools
The formatted snippet helps him reason, but the real check happens in DevTools and the application logs.
4. Fix the source file
He updates the original TypeScript source, not the beautified minified output. The build system creates a fresh bundle after the fix.
What Beautifying Can't Fix
Beautifying restores readable formatting, but minification is a one-way process for certain transformations:
| Transformation | Reversible? | What You See |
|---|---|---|
| Whitespace removal | Yes | Beautifier adds it back perfectly |
| Comment removal | No | Comments are gone permanently |
| Variable renaming (mangling) | No | calculateTotal → a, readable names are lost |
| Dead code removal | No | Removed code is gone |
| Constant folding | No | 60*60*24 becomes 86400 |
If you're trying to read heavily mangled production code, source maps are a better approach. Source maps link minified code back to the original source with full variable names and comments intact.
JavaScript Syntax That Needs Extra Care
| Syntax | Why it can be tricky | How to review |
|---|---|---|
| Template literals | They can contain braces, newlines, and nested expressions | Check strings with backticks after formatting |
| Regex literals | Slashes can look like division or comments to simple tools | Review patterns that contain escaped slashes |
| Arrow functions | Concise returns can be hard to read after minification | Look for implicit returns and object literal returns |
| Optional chaining | Short chains can become dense in bundled output | Check whether a missing value is intentionally allowed |
| Async functions | Await order and error handling matter more than spacing | Look for missing catch blocks and unhandled promises |
Readable JavaScript Review Checklist
- Use the formatted output for inspection. Do not treat it as recovered source code when names, comments, and source maps are missing.
- Trace side effects. Look for DOM writes, network requests, storage access, timers, and event listeners.
- Check error paths. Minified code often hides catch blocks and early returns. Formatting makes those branches easier to follow.
- Avoid editing generated bundles. Fix the original source and rebuild. Direct edits to bundled files are hard to maintain.
- Prefer source maps when available. A source map gives you original file names and line numbers, which a beautifier cannot recreate.
When Beautified Output Is Enough
A formatter is useful for inspection, but it is not always the right final artefact. Use the output according to the task you are doing.
| Task | Use beautified output? | Reason |
|---|---|---|
| Reading a third-party snippet | Yes, for inspection | Readable structure helps you understand side effects |
| Committing project code | Use your project formatter | Project tools know your syntax, parser, and style settings |
| Debugging production bundle code | Yes, if no source map exists | It can reveal branches, loops, and nested calls |
| Recovering lost source | Not fully | Comments, meaningful names, and module boundaries may be gone |
Related Tools
How to use this tool
Paste minified or messy JavaScript into the input area
Choose your preferred indentation (2 or 4 spaces)
Click Beautify and copy the formatted result
Common uses
- Reading minified third-party scripts for security review
- Debugging production JavaScript via source inspection
- Reformatting code snippets from Stack Overflow
- Making auto-generated JavaScript readable for editing
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Frequently Asked Questions
What does a JS beautifier do?
Does this handle ES6+ syntax?
Is this safe for production code?
Why can't I read minified JavaScript?
Should I use 2-space or 4-space indentation?
What's the difference between a beautifier and a linter?
Can I beautify TypeScript?
Is my code sent to a server?
How do I beautify JS in Chrome DevTools?
Will beautifying change my code's behaviour?
Can I beautify obfuscated code?
When should I use Prettier instead?
Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.