JavaScript Formatter
Beautify and format JavaScript code with proper indentation.
Input
Output
Beautify and format JavaScript code with proper indentation.
This free JavaScript Formatter from KX Toolkit is part of our all-in-one online toolkit. It runs entirely in your browser, so your data never leaves your device for client-side operations. 100% free, forever - no paywall, no credit card, no trial.
How to use the JavaScript Formatter
- Paste your input - JSON, regex pattern, JWT, URL etc.
- Pick any flags or options the tool supports.
- Click the action button (Format, Test, Decode).
- Copy the result or download it as a file.
What you can do with the JavaScript Formatter
- Format and validate API responses while debugging.
- Test regex patterns against real input before deploying.
- Decode JWTs to inspect claims and expiry.
- Generate UUIDs for migrations, tests and seeders.
Why use KX Toolkit's JavaScript Formatter
- Browser-based: Works on Windows, macOS, Linux, iOS and Android - no install, no extension.
- Privacy-first: Client-side tools never upload your data; server-side tools delete files right after processing.
- Mobile-friendly: Full feature parity on phones and tablets - not a stripped-down view.
- Fast: Optimised for instant feedback. No artificial waiting screens, no email-gated downloads.
- One hub for everything: 300+ tools across SEO, text, image, PDF, code, color, calculators and more - skip switching between sites.
Tips for the best results
Bookmark the most-used tools - your browser bookmark bar is faster than retyping the URL every time.
Related Developer Tools
If you find this tool useful, explore the full Developer Tools collection or browse our complete tool directory. KX Toolkit is built for marketers, developers, designers, students and anyone who needs a quick utility without signing up for yet another SaaS.
Does the formatter change how my JavaScript executes?
No, except for one subtle case: automatic semicolon insertion. Adding line breaks in the wrong place can change ASI behavior, particularly around return, throw, yield, and continue statements. Quality formatters know these rules and avoid breaking them. Always run your test suite after a large reformat to catch any edge cases the parser handled differently.
Should I commit semicolons or rely on ASI?
Either is fine, but pick one and have the formatter enforce it. Going semicolon-less is cleaner visually but requires care with leading parentheses or square brackets, which can cause two statements to merge. Most teams keep semicolons because the rule is simpler and tooling support is universal. The important thing is consistency across the codebase.
How does formatting affect minified bundles in production?
It does not - production builds are minified, so any whitespace changes during development disappear at build time. Formatting matters for source files in version control, where readability and clean diffs help reviewers. Never check minified output into source control; always commit the formatted source and let the build step minify on the way out.
Will it format TypeScript and JSX as well?
Most modern formatters support JavaScript, TypeScript, JSX, and TSX in one pass because the parsers share a foundation. The output handles JSX-specific rules like attribute wrapping and self-closing tags, plus TypeScript syntax such as type annotations and generics. Make sure the formatter has the right parser configured for the file extension to avoid syntax errors.
Why do trailing commas keep appearing in my code?
Modern formatters add trailing commas in arrays, objects, and function arguments because they produce smaller diffs when items are added later. ES2017+ allows them everywhere except after a rest parameter. If a build target is older than ES5 the formatter should detect that and skip them; otherwise configure the trailing-comma option to match your tooling.
Should the formatter run on save or only in CI?
Both. Editor-on-save formatting catches issues immediately and removes formatting noise from code review. A CI check guarantees that every commit conforms even when a contributor lacks editor integration. Tools like Prettier paired with lint-staged on a pre-commit hook strike the same balance without slowing down regular pushes.
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