JSX Formatter & Validator

Format JSX and React components in your browser

Paste a React component, a snippet from documentation or JSX copied from an AI assistant and get it back neatly indented, with long elements broken onto separate lines and multi-line JSX wrapped in parentheses the way most React codebases write it. Validation catches the mistakes that break a component before it renders: unclosed tags, mismatched closing tags and broken expressions in curly braces. The formatter uses Prettier with the Babel parser and runs entirely on your device.

What can you do?

1. 1. Readable JSX layout
   Nested elements get their own indentation level, long attribute lists are split one per line, and returned JSX is wrapped in parentheses so the structure is obvious.
2. 2. Modern JavaScript included
   Hooks, arrow functions, destructuring, optional chaining, fragments (<>…</>), spread props and ES module imports all format correctly.
3. 3. JSX syntax validation
   Find unclosed or mismatched tags and broken {expressions} with the line and column of the problem, e.g. “Line 3, column 19: Unterminated JSX contents.”
4. 4. Tag count
   See how many JSX tags a component contains, a quick signal that it might be time to split it into smaller components.

Why use a JSX formatter?

JSX mixes markup and JavaScript, which makes inconsistent formatting especially hard to read. A component that returns one long line of nested elements hides its structure, and a missing closing tag can be almost impossible to spot by eye.

Formatting gives every element a predictable place, so the component tree reads top to bottom like the UI it renders. It's handy for cleaning up snippets before pasting them into a project, documentation or a code review comment.

How to format a React component

1. 1. Paste the JSX
   A full component file works, and so does a single function or a fragment of markup inside a JavaScript expression.
2. 2. Click format
   The code is checked first. If it's valid, the formatted version appears in the result panel.
3. 3. Fix errors if any
   For an unclosed tag, the reported position is usually where the parser realised the tag was never closed. Look at the element that starts just before it.
4. 4. Copy the component
   Copy the result into your editor, documentation or Storybook story.

Example: a one-line component, formatted

export default function Counter({start=0}){const [count,setCount]=useState(start);return <div className="counter"><p>Count: {count}</p><button onClick={()=>setCount(count+1)}>Add one</button></div>}

export default function Counter({ start = 0 }) {
  const [count, setCount] = useState(start);
  return (
    <div className="counter">
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Add one</button>
    </div>
  );
}

Common JSX errors and how to fix them

Some mistakes are valid syntax and won't be flagged: React expects className and htmlFor instead of class and for, but the parser accepts both because JSX attributes can have any name. React reports those in the browser console at runtime.

Frequently asked questions

Related tools

Writing typed React? Use the TypeScript and TSX formatter. Styling components with Sass? Tidy the stylesheet with the SCSS formatter.

• TypeScript Formatter & Validator – Format TypeScript and TSX and check them for syntax errors.
• JavaScript Formatter & Validator – Format, lint and minify JavaScript snippets.
• SCSS Formatter, Validator & Minifier – Beautify, validate and safely minify Sass (SCSS).
• Vue Formatter & Validator – Format Vue single-file components and check every block.
• Markdown Formatter – Give README and docs files a consistent Markdown style.