How to use the JavaScript Formatter / Beautifier
Format JavaScript in three steps:
1
Paste your JavaScript
Paste any JavaScript — minified, messy, or auto-generated — into the input panel. You can also upload a .js or .mjs file using the upload icon.
2
Configure Prettier options and click Format
Choose indent size (2 or 4 spaces), quote style (single/double), semicolons (always/never), and print width. Click 'Format JS' to run Prettier.
3
Copy or download
Copy the formatted code to clipboard, or download it as a .js file. The stats bar shows line count, character count, and file size.
When to use this tool
Use the JavaScript formatter when you need consistently styled, readable code:
- →Formatting minified or bundled JavaScript back into readable code for debugging
- →Standardising code style across a file or snippet before committing to a repository
- →Formatting JavaScript snippets found in Stack Overflow answers or GitHub Gists
- →Cleaning up AI-generated or auto-generated JS code before reviewing it
- →Preparing code for articles, documentation, README files, or tutorial content
- →Reformatting legacy code before a refactor or code review
- →Making third-party library source code readable before patching or forking it
Frequently asked questions
Q:Which JavaScript syntax versions and features are supported?
Prettier's Babel parser supports all modern JavaScript including ES2024, optional chaining (?.), nullish coalescing (??), logical assignment operators (&&=, ||=, ??=), class fields, private methods, top-level await, dynamic imports, BigInt literals, and JSX. CommonJS (require/module.exports) and ES Modules (import/export) are both supported.
Q:Can I use this to format JSX (React) code?
Yes — Prettier's Babel parser handles JSX natively. Paste JSX including React component definitions, hooks, conditional rendering, and embedded expressions, and Prettier will format it correctly. For TypeScript React files (.tsx), use the TypeScript Formatter tool which uses Prettier's TypeScript parser instead.
Q:What is Prettier and why is it the industry standard?
Prettier is an opinionated code formatter created in 2017. It parses your code into an AST (Abstract Syntax Tree) and reprints it from scratch according to its own rules, guaranteeing that the output always looks the same regardless of how the input was written. It is used by millions of developers worldwide and is the default formatter in VS Code, WebStorm, and most modern editor setups. Opinionated means fewer arguments about style and more consistency across teams.
Q:Why is the formatter slower to start than the CSS or HTML tools?
The JavaScript formatter loads Prettier and its Babel/estree plugins from CDN (unpkg.com) on first use — this takes 1–3 seconds on most connections. After the initial load, formatting is instant. The CSS and HTML formatters use lightweight custom parsers built into the page, so they load immediately.
Q:Does Prettier change the logic or behaviour of my JavaScript?
No — Prettier only affects formatting (indentation, line breaks, spacing, quote style, trailing commas). It never modifies variable names, reorders statements, changes operators, or alters any semantic aspect of the code. The formatted output is functionally identical to the input.
Q:What do the 'semicolons: never' and 'single quotes' options mean?
'Semicolons: never' follows the JavaScript style used by some teams (notably StandardJS) that omits semicolons, relying on ASI (Automatic Semicolon Insertion). Prettier handles this safely by inserting semicolons only in the edge cases where omitting them would cause parse errors. 'Single quotes' uses single-quote strings instead of double quotes for string literals, matching the common Node.js/React convention.
Q:Can I format Node.js, Express, or browser JavaScript?
Yes — Prettier's JavaScript formatter handles all JavaScript environments including Node.js modules (CommonJS and ESM), browser scripts, Express/Koa/Fastify servers, React/Vue/Svelte component scripts, and utility libraries. The formatter is environment-agnostic and only cares about JavaScript syntax, not the runtime it targets.