Upload or paste JavaScript and format it into clean, readable code you can copy or download in seconds.
Beautify and format JavaScript code instantly in your browser. XConvert's free JS Formatter adds proper indentation, consistent spacing, and organized line breaks so your code is easy to read, debug, and maintain — no server uploads, no installations required.
Step 1 — Paste or Upload Your JavaScript
Open the XConvert JS Formatter and paste your minified or messy JavaScript into the input panel. You can also drag-and-drop a .js file directly onto the editor. The tool accepts any JavaScript — from a short function to an entire application bundle.
Step 2 — Choose Your Formatting Options Select your preferred indentation (2 spaces, 4 spaces, or tabs) from the toolbar. Additional options include brace style (same-line or next-line), semicolon insertion, single vs. double quotes for strings, and maximum line length for wrapping long expressions. These settings let you match your project's style guide or personal preference.
Step 3 — Click "Format" Press the Format button. The tool parses your JavaScript entirely inside your browser using a full-featured JavaScript parser, restructures the whitespace and formatting according to your chosen options, and renders the result with syntax highlighting. Keywords, strings, numbers, operators, and comments each receive distinct colors.
Step 4 — Copy or Download the Result
Click Copy to place the formatted JavaScript on your clipboard, or click Download to save it as a .js file. The output is ready to paste into your code editor, documentation, or version-control system.
JavaScript formatting — also called JS beautifying or pretty-printing — is the process of restructuring a JavaScript file's whitespace and style to make it human-readable. A formatter adds consistent indentation inside blocks, places statements on separate lines, inserts spaces around operators, aligns braces and brackets, and applies consistent quoting and semicolon conventions.
The code's behavior does not change. Every variable, function, expression, and statement remains semantically identical. Formatting is a purely cosmetic transformation that improves the developer experience. When you can see the control flow, nesting depth, and logical structure at a glance, you debug faster, review more effectively, and introduce fewer bugs during edits.
Consistent formatting is especially important in team environments. Style inconsistencies — tabs vs. spaces, semicolons vs. no semicolons, brace placement — create noisy diffs, slow down code reviews, and distract from the actual logic changes. A formatter eliminates these debates by enforcing a single style automatically. XConvert's JS Formatter gives you this capability without installing any tooling.
| Feature | XConvert JS Formatter | Prettier (CLI/IDE) | ESLint --fix | js-beautify (CLI) |
|---|---|---|---|---|
| Cost | Free | Free | Free | Free |
| Installation | None (browser-based) | Required | Required | Required |
| Privacy | Client-side only | Local | Local | Local |
| Syntax Highlighting | ✅ | Editor-dependent | ❌ | ❌ |
| Custom Indentation | ✅ | ✅ | ✅ | ✅ |
| Brace Style Options | ✅ | Limited | ✅ | ✅ |
| Quote Style | ✅ | ✅ | ✅ | ❌ |
| Semicolon Handling | ✅ | ✅ | ✅ | ❌ |
| Drag-and-Drop Upload | ✅ | ❌ | ❌ | ❌ |
| Works Offline | ✅ (after page load) | ✅ | ✅ | ✅ |
Unminifying Production JavaScript — When debugging a live website, you often encounter minified JavaScript bundles with single-character variable names and no whitespace. Paste the minified code into the formatter to restore readable structure, making it possible to set breakpoints, trace logic, and understand the control flow even without source maps.
Standardizing Code Style — Before committing JavaScript to a shared repository, format it with consistent settings. This eliminates style debates in code reviews and keeps diffs focused on logic changes rather than whitespace differences. Teams that adopt a single formatting standard spend less time on cosmetic feedback and more time on architecture and correctness.
Reviewing Third-Party Libraries — When evaluating an open-source library, SDK, or npm package, formatting the source makes it easier to understand the architecture, identify entry points, assess code quality, and determine whether the library meets your needs before adding it as a dependency.
Preparing Documentation Examples — JavaScript snippets in tutorials, API docs, README files, or developer guides should be well-formatted so readers can follow the logic without confusion. The formatter ensures professional, consistent examples that are easy to copy, paste, and adapt.
Debugging Bookmarklets — Bookmarklets are JavaScript snippets compressed into a single line for use in browser bookmarks. Formatting them reveals the full logic so you can understand, modify, debug, or audit them for security before adding them to your browser.
Learning JavaScript — Beginners benefit from seeing code in a clean, structured form. The visual hierarchy of blocks, functions, and control flow reinforces programming concepts like scope, closures, and asynchronous patterns. Formatted code with syntax highlighting makes examples easier to follow and experiment with.
XConvert's JS Formatter uses a client-side JavaScript parser that builds a full Abstract Syntax Tree (AST) from the input code. Unlike regex-based formatters that can be confused by edge cases (strings containing braces, template literals, regular expressions), an AST-based approach understands the actual structure of the code. The formatter walks the AST and emits formatted output according to the user's chosen style rules, handling every ECMAScript feature including arrow functions, destructuring, async/await, optional chaining, nullish coalescing, class fields, private class methods, and top-level await. This comprehensive parser support means you can format modern JavaScript without worrying about syntax errors or misformatted output.
Syntax highlighting is applied during the output rendering phase. The formatter tokenizes the output and wraps keywords (const, function, if, return, async, await), string literals, numeric literals, operators, comments, and identifiers in styled elements. Template literal expressions (${...}) are highlighted distinctly from the surrounding string, and regular expression literals are distinguished from division operators. The color scheme follows accessible contrast ratios (WCAG AA) so that the highlighting is usable for people with color-vision deficiencies, and it works well in both light and dark browser themes.
All processing runs in the browser with no server communication. Your JavaScript — which may contain proprietary business logic, API keys embedded in test files, unreleased feature code, or internal algorithm implementations — stays on your machine. The formatter handles files up to several megabytes and works in all modern browsers including Chrome, Firefox, Safari, and Edge. For very large bundles (10 MB+), consider formatting individual modules rather than the entire bundle. After formatting, you can use the JS Minifier to compress the code back down for production deployment, or paste it into the HTML Formatter if it is part of an inline <script> block.
Use Consistent Settings — Pick one set of formatting options (indentation, quotes, semicolons, brace style) and use it across your entire project. Consistency reduces noise in version-control diffs and makes the codebase easier to navigate.
Format Before Reviewing — Run JavaScript through the formatter before submitting it for code review. Reviewers can focus on logic and architecture rather than whitespace inconsistencies.
Handle Syntax Errors First — The formatter requires syntactically valid JavaScript. If your code contains errors (missing brackets, unterminated strings), the parser will fail. Fix syntax errors in your editor first, then format.
Preserve Comments — The formatter keeps all comments intact, including JSDoc blocks, inline comments, and TODO markers. Comments survive formatting and are properly indented relative to the surrounding code.
Combine with Minification — Use the formatter during development for readability, then run the JS Minifier as a build step to compress the code before deploying to production.
Try Different Styles — If you are starting a new project and have not settled on a style guide, experiment with different formatting options to find what feels most readable to your team. Once decided, document the settings and apply them consistently.
No. All processing happens client-side in your browser. Your JavaScript never leaves your device, making it safe for proprietary or sensitive code. There are zero network requests after the initial page load.
No. Formatting only modifies whitespace, line breaks, and stylistic choices (quotes, semicolons). The code's behavior remains identical. The AST round-trip guarantees semantic equivalence — the formatted code produces the exact same results as the original.
You can choose 2 spaces, 4 spaces, or tab characters. The default is 2 spaces, which is the most common convention in the JavaScript ecosystem.
The formatter is designed for standard JavaScript (ECMAScript). TypeScript files that use type annotations, interfaces, enums, generics, or other TypeScript-specific syntax may not parse correctly. Use a TypeScript-aware formatter like Prettier with the TypeScript plugin for .ts and .tsx files.
Basic JSX support is included, but complex React components with advanced patterns may not parse perfectly. For production React projects, Prettier with JSX support is recommended. For quick formatting of simple JSX snippets, this tool works well.
There is no hard limit, but performance is best for files under 5 MB. Very large files may take a few seconds to process. For bundles exceeding 10 MB, format individual source files instead. The tool works in all modern browsers and performance varies based on your device's processing power and available memory.
You can configure this behavior. The "Insert Semicolons" option adds semicolons where ASI (Automatic Semicolon Insertion) would apply, making the code more explicit. The "Remove Semicolons" option strips them where safe, following the no-semicolons style popular in some JavaScript communities. By default, existing semicolons are preserved as-is.
Yes. The formatter fully supports ES module syntax, including import, export, export default, dynamic import(), re-exports, and namespace imports. Module declarations are formatted with the same indentation and spacing rules as the rest of the code, ensuring a consistent look throughout your module files.
The JS Formatter adds whitespace for readability, while the JS Minifier removes whitespace, shortens variable names, and applies other optimizations to reduce file size. They are complementary — format for development, minify for production.
Yes. Once the page has loaded, all formatting happens locally. You can disconnect from the internet and continue working without interruption.