JS Beautifier

A JS Beautifier (also called a JavaScript Formatter or JavaScript Pretty Printer) takes minified, inline, or inconsistently indented JavaScript and reformats it with consistent indentation, line breaks, and spacing to improve readability and maintainability. It is the counterpart to a JS Minifier — a beautifier adds structure for developers while a minifier removes it for delivery.

Paste your JavaScript into the input panel or open a local .js file. Choose your indentation style (2 spaces, 4 spaces, or tab), configure comment and blank-line options, then click Beautify JS or enable Live mode. Review the formatted output and diagnostics panel, then copy or download the result.

Yes. The beautifier supports 2-space indentation (the most common convention in web projects and used by Prettier and ESLint defaults), 4-space indentation (common in many enterprise JavaScript and TypeScript codebases), and tab indentation. The indent setting applies consistently to every nesting level.

Yes. The beautifier tokenizes the input before reformatting, so minified single-line JavaScript is expanded into readable multi-line form. Strings, template literals, regex literals, and comments are protected during tokenization so their content is never corrupted.

Yes. The tokenizer extracts all quoted strings (single-quoted and double-quoted), template literals (backtick strings), and regex literals before reformatting. This ensures that whitespace, braces, or other structural characters inside strings are not treated as code structure. Template literal multi-line content is preserved exactly.

The diagnostics panel checks for: unclosed block comments, mismatched brace counts, mismatched parenthesis counts, debugger statements (which must be removed before production), console.log/warn/error calls (which should be reviewed before deployment), TODO and FIXME comments, and use of == instead of === (loose equality). These are heuristic checks to flag common review items.

You can enable Remove comments to strip all single-line and block comments from the output. With Preserve /** JSDoc checked, JSDoc-style block comments (starting with /**) are kept even when comment removal is on. JSDoc comments contain type annotations, parameter docs, and return-value documentation that should not be lost.

When enabled, a blank line is added after each closing brace at the top level (depth 0) to visually separate functions, classes, and other top-level declarations. This matches the Prettier default style and makes long files significantly easier to scan.

The beautifier handles arrow functions as part of general expression tokenization. Arrow => is treated as an operator token. The indentation and spacing around arrow function bodies follows the same brace rules as regular functions. Single-expression arrow functions without braces are kept on one line if the source has them that way.

Yes. Import and export statements are tokenized as identifier tokens and are formatted with the same indentation and spacing rules as other statements. Named exports, default exports, re-exports, and dynamic import() calls are preserved correctly.

The beautifier handles TypeScript syntax including type annotations, interface declarations, enum blocks, generic type parameters, and type assertions as generic token streams. It does not interpret TypeScript semantics. For large TypeScript projects, use a project-aware formatter like Prettier with the TypeScript plugin.

Yes. Click Open .js to select a local .js, .mjs, .cjs, or .ts file. The file is read by the browser's FileReader API entirely in memory. No data is sent to any server. This allows you to format private source code, company scripts, or confidential project files without any data leaving your device.

When Live mode is enabled, the output panel updates automatically on every keystroke in the input. This is useful for rapid iteration. For large files, disable Live mode and click Beautify JS explicitly to format only when ready.

Yes. Click Copy JS to copy the entire formatted output to the clipboard. The copied text includes consistent indentation and newlines from the formatter output.

Yes. Click ↓ .js to download the beautified output as beautified.js using a Blob URL in the browser. No server is involved.

The recent beautify sessions panel logs up to eight recent formatting operations. Each entry shows the first line of the input and the timestamp. Click any entry to reload that JavaScript for further editing. History is in-memory only and clears when you close or reload the page.

Prettier is a project-installed code formatter with full AST-based parsing, opinionated style enforcement, multi-language support, editor plugins, and CI integration. ToolsSonic is a fast browser-based tool for one-off formatting, quick inspection, and debugging without requiring Node.js, a project configuration, or command-line access. Use Prettier in your project build pipeline and ToolsSonic for quick ad-hoc formatting.

No. Open DevTools Network tab while using the tool. You will see zero outbound requests triggered by formatting. The entire tool — tokenizer, beautifier, lint engine — is implemented in vanilla JavaScript running in your browser with no external dependencies. Nothing is uploaded.