JavaScript Formatter
Real Prettier formatting, right in your browser: paste messy JS, get clean code with your style options.
Privacy: formatting runs entirely in your browser — your code never leaves this page.
How to use
- Paste your JavaScript or JSX into the input.
- Toggle semicolons and quote style to match your conventions.
- Copy the formatted output — errors, if any, are reported instead of guessed.
Frequently asked questions
What engine does this formatter use?
Prettier 3 — the same code formatter used in professional editors — running fully in your browser via its standalone build (babel parser, estree printer). Output matches Prettier defaults: 2-space indent, 100-character print width, double quotes by default.
What happens with syntax errors?
Prettier needs parseable code. If your JavaScript does not parse, the tool shows a clear error instead of half-formatting — fix the reported problem and try again.
Does it support JSX and modern syntax?
Yes: the babel parser handles JSX, optional chaining, nullish coalescing, class fields and other current syntax. Template literals with Chinese or emoji identifiers are preserved.
What are the semicolon and quote options?
Check "omit semicolons" for Prettier's semi:false style, and "single quotes" for singleQuote:true — the two toggles people most often need to match their team style guide.
Is my code uploaded anywhere?
No. Formatting runs entirely in your browser — nothing is sent to any server, so it is safe for proprietary code.