✨ Code Beautifier — HTML, CSS & JS Formatter

Complete Guide: Code Beautifier — HTML, CSS & JavaScript Formatter Powered by js-beautify

What Is the Code Beautifier and Why It Matters

The Code Beautifier is a browser-based formatter for HTML, CSS, and JavaScript code, powered by the open-source js-beautify library — the same engine used in thousands of developer tools, VS Code extensions, and build pipelines. It takes inconsistently indented, minified, or poorly structured code and reformats it according to configurable style rules: consistent indentation, proper line breaks, operator spacing, and correct tag/brace alignment.

Why does this matter? Code style inconsistency is a real maintenance burden. When a team of three developers each uses different indentation (tabs vs spaces, 2 vs 4 spaces), different brace styles (same line vs next line), and different quote preferences, the codebase becomes harder to read and the Git history fills with noisy whitespace-only diffs that obscure actual changes. A formatter normalises all of this automatically. The human reviewer can focus on logic, not style.

Even for solo developers, reformatting is essential when: copying code from Stack Overflow (almost always poorly formatted), reverse-engineering minified production JavaScript, cleaning up AI-generated code that used inconsistent conventions, or returning to a file written under time pressure that was never properly organised.

The js-beautify library is battle-tested across millions of uses and handles real-world quirks: JSX-like syntax in JS files, CSS preprocessor syntax, template literals with embedded expressions, and HTML with inline JavaScript and CSS blocks — all correctly formatted in a single pass.

How to Use This Code Beautifier

1. Select the language from the dropdown: HTML, CSS, or JavaScript. This determines which js-beautify engine and rule set is applied.
2. Paste your code into the input editor. The tool accepts minified single-line code, multi-line code with inconsistent indentation, or partially formatted code.
3. Configure formatting options (optional): choose indentation size (2 or 4 spaces, or tab), max line length, quote style (single or double for JS), brace style (collapse, expand, end-expand), and whether to preserve existing new lines.
4. Click "Beautify" (or press Ctrl+Enter). The formatted result appears in the right panel with syntax highlighting.
5. Copy the output with the Copy button, or download as a file. The before/after character count is shown so you can see how much the formatting changed the file.

HTML Formatting — What Gets Fixed

The HTML beautifier handles: inconsistent tag indentation (normalises child elements to be indented relative to their parent), improper attribute formatting (one attribute per line for tags with many attributes, preserving attribute order), self-closing tag normalisation, preservation of inline vs block element distinctions (inline elements like <span> don't get unnecessarily broken onto separate lines the way block elements like <div> do), and intelligent handling of <pre> and <textarea> blocks where whitespace is significant and must not be changed.

It also formats embedded JavaScript (<script> blocks) and CSS (<style> blocks) within HTML files — applying the respective language rules to each section.

CSS Formatting — What Gets Fixed

The CSS beautifier normalises: selector formatting (each selector on its own line in comma-separated lists), property declaration ordering (one property per line), value spacing (space after colon, no space before), brace placement (opening brace on same line as selector, closing brace on its own line), and empty line insertion between rule blocks for readability. It handles standard CSS, CSS Custom Properties, media queries, keyframe animations, and most preprocessor-like syntax (variable declarations, nesting in SCSS-compatible mode).

JavaScript Formatting — What Gets Fixed

The JavaScript beautifier is the most powerful of the three. It handles: brace style (configurable — same line for K&R style, next line for Allman style), statement indentation, operator spacing (spaces around =, +, === etc.), function declaration formatting, arrow function formatting, template literal preservation, comment preservation and alignment, and semicolon normalisation (add or remove based on your preference). It correctly handles ES6+ syntax including destructuring, spread operators, async/await, and optional chaining.

Practical Use Cases with Examples

Cleaning up minified vendor JavaScript: You've copied a vendored library to debug a production issue. The file is a single 4,000-character line. Paste into the beautifier, select JavaScript, click Beautify — output is 120 lines of readable code in under a second. Now you can set breakpoints and understand the logic.

Normalising a team codebase: Two developers have been working on a CSS file simultaneously — one uses 2-space indentation, one uses 4-space, and neither uses consistent brace placement. Paste the combined file, configure to 2-space indent, and run the beautifier. All style inconsistencies are resolved in one operation.

Cleaning AI-generated code: You've asked an AI assistant to generate a JavaScript utility function. The output uses double quotes in some places, single quotes in others, inconsistent spacing around operators, and no empty lines between logical sections. Paste into the beautifier with your preferred style settings and get clean, consistently formatted output.

Preparing code for a code review: Before submitting a pull request, run all changed files through the beautifier to ensure no incidental whitespace changes appear in the diff. This keeps code reviews focused on logic, not formatting.

Reading a third-party HTML template: A purchased HTML template has been minified for production delivery. Paste the HTML into the beautifier to get a readable structure for customisation. The indented output immediately shows the DOM hierarchy and where to insert your content.

Formatting Options Explained

• Indent size: 2 spaces is the modern default (used by Google style guides, Airbnb JS guide, Bootstrap). 4 spaces is older convention and common in Python communities. Tab indentation is preferred by some accessibility guidelines (allows individual developers to set their own tab width in their editor).
• Brace style (JS): "collapse" = same-line opening brace (K&R/JavaScript default). "expand" = opening brace on new line (Allman style). "end-expand" = closing brace on new line only.
• Preserve new lines: When enabled, existing intentional blank lines (like separating logical sections) are preserved even if the formatter wouldn't add them itself. Disable this for maximum normalisation.
• Quote style (JS): Normalize all string literals to single or double quotes. Strings containing the opposite quote type are left with their original quote to avoid escaping.
• Max line length: Lines longer than this will be wrapped where possible (function arguments, array items, object properties). 80 is the traditional terminal width; 120 is common for modern wide monitors.

Code Beautifier vs Linter vs Minifier

A beautifier (formatter) reformats code for readability — it changes whitespace and style but never semantics. A linter (like ESLint for JS or stylelint for CSS) checks for logical errors, potential bugs, deprecated patterns, and enforces additional style rules that a formatter cannot — it reports issues but in many cases doesn't auto-fix them. A minifier (like UglifyJS or cssnano) does the opposite of a beautifier — it removes all unnecessary whitespace and shortens identifiers to reduce file size. For a complete development workflow: beautify during development for readability, lint for correctness, minify for production deployment.

For minifying your output rather than beautifying it, use the dedicated CSS Minifier or JavaScript minifier. For formatting SQL specifically, use the SQL Formatter. For a regex tester to validate patterns in your JavaScript code, see the Regex Tester.

Frequently Asked Questions

Is js-beautify the same as Prettier?
No. Prettier is a more opinionated formatter that enforces a fixed style with few configurable options, prioritising consistency over personal preference. js-beautify is more configurable and more permissive — it adapts to your style rather than enforcing its own. Both are excellent for different workflows. This tool uses js-beautify because its configurability makes it more useful as a general-purpose web tool.

Will the beautifier change my code's logic or behaviour?
No. The beautifier only changes whitespace (spaces, tabs, newlines) and quote normalisation. It never reorders statements, changes variable names, adds or removes semicolons unless you explicitly configure semicolon normalisation, or alters any logic. The output is always semantically identical to the input.

Can I beautify TypeScript or JSX files?
Select "JavaScript" mode. js-beautify handles most TypeScript and JSX syntax correctly — it formats the JavaScript portions and leaves TypeScript type annotations and JSX tags in place. For complex TypeScript with advanced generic syntax, a TypeScript-specific formatter like the TypeScript compiler's own tsc --pretty or Prettier with the TypeScript plugin will be more accurate.

What happens if my code has syntax errors?
The beautifier attempts to format even syntactically invalid code on a best-effort basis — it may produce partially formatted output. If the code is severely malformed, the output will indicate that errors were encountered. Fix syntax errors first (use the browser console or a linter) for clean results.