Input HTML
Output
Formatted output appears here...
What this tool does
Free HTML formatter -- beautify, minify, and validate HTML code online
This free HTML formatter provides three modes in a single tool. Format mode takes any HTML -- whether a single long line from a CMS output, minified production code, or manually written code with inconsistent indentation -- and reformats it with two-space indentation that accurately reflects the nesting depth of every element. The side-by-side layout lets you paste raw HTML on the left and immediately see the formatted, syntax-highlighted output on the right. Output statistics show the line count and file size, and any structural errors found during formatting are listed below the editors so you can fix them without switching to a separate validator.
The formatter works by first tokenizing the HTML into individual tags and text nodes, then rebuilding the output with calculated indentation based on whether each tag opens a new nesting level, closes one, or is a self-closing void element. Void elements like br, hr, img, input, link, and meta are correctly identified and never increase the indent level. Raw content tags like script, style, pre, and textarea are treated specially -- their inner content is preserved without reformatting since whitespace is semantically significant in those contexts. The syntax highlighter then applies color coding to tag names, attributes, values, and comments using the same color conventions as VS Code and other popular editors.
HTML formatting and minification serve complementary roles in a professional development workflow. During development, well-formatted HTML makes code reviews easier, helps onboarding new team members, produces meaningful Git diffs, and makes debugging layout issues much faster. Before deploying to production, minification removes all developer-oriented formatting -- comments, indentation, and line breaks -- to produce the smallest possible file that browsers can parse just as efficiently as the formatted version. A typical HTML file sees 15-30% size reduction from minification, with even greater savings when combined with gzip or Brotli compression at the web server level.
Features and capabilities
Auto-indentation
Reformats HTML with two-space indentation based on element nesting depth, making parent-child relationships immediately visible.
Minification
Removes comments, collapses whitespace, and strips line breaks to reduce HTML file size by 15-30% for faster page loads.
Tag validation
Detects mismatched closing tags and unclosed elements, showing specific error messages for each structural problem found.
Syntax highlighting
Colors tag names (orange), attributes (purple), values (green), and comments (grey) matching VS Code's default HTML color scheme.
Void element support
Correctly handles self-closing void elements (br, hr, img, input, meta, link) that do not increase indentation depth.
Raw tag preservation
Content inside script, style, pre, and textarea is preserved unchanged since whitespace is semantically meaningful there.
Output statistics
Displays line count, output file size in KB, and percentage size reduction for minified output relative to the input.
One-click copy
Copies the formatted or minified output to the clipboard with a single click and shows a visual confirmation.
Sample HTML loader
Loads a representative multi-section HTML document instantly for users who want to explore the formatter without their own code.
100% client-side
All formatting, minification, and validation runs in the browser -- nothing is sent to any server at any point.
Examples
HTML formatter examples -- before and after formatting, minification, and validation
These examples show the formatter, minifier, and validator in action with realistic HTML inputs and the results each mode produces.
ExcellentFormat mode -- CMS-generated single-line HTML beautified
Input (single line from WordPress):
<div class="entry"><h2>Title</h2><p>Paragraph <a href="/page">link</a>.</p></div>
Output (formatted):
<div class="entry">
<h2>Title</h2>
<p>Paragraph <a href="/page">link</a>.</p>
</div>
CMS platforms like WordPress, Shopify, and Drupal often output HTML as a single long line to reduce page weight. Pasting this into the formatter instantly reveals the element hierarchy, making it easy to identify structure, add CSS selectors, or debug layout issues. The indentation accurately reflects nesting depth and the output is ready to paste into a code editor.
GoodMinify mode -- production HTML with 24% size reduction
Input (2.8 KB formatted):
<!DOCTYPE html>
<html lang="en">
<head>
<!-- Analytics -->
<meta charset="UTF-8">
<title>My Page</title>
</head>
...
Output (2.1 KB minified, -24%):
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>My Page</title></head>...
Minification removed the comment and all indentation whitespace, reducing the file by 24% before any server-side compression. When the web server applies gzip on top of this, the total compressed size drops further. For high-traffic pages, even small reductions in HTML size translate to meaningful bandwidth savings at scale and contribute to Core Web Vitals scores.
PassValidate mode -- structurally correct HTML with no errors
Input:
<nav>
<ul>
<li><a href="/">Home</a></li>
<li><a href="/about">About</a></li>
</ul>
</nav>
Result: No structural errors detected
All opening tags are properly closed in the correct order, void elements are handled correctly, and the nesting hierarchy is valid. A clean validation result means the HTML will parse consistently across all browsers and assistive technologies. This is the baseline structural quality standard for any production HTML.
FailValidate mode -- mismatched and unclosed tags detected
Input:
<div>
<h1>Title</h2>
<p>Paragraph text
</div>
Errors:
⚠ Mismatched tag: </h2> closes <h1>
⚠ Unclosed tag: <p>
Two structural errors were found: an h1 element closed with an h2 closing tag, and a paragraph element with no closing tag. Browsers silently correct these errors using their own recovery rules, but different browsers may produce different DOM trees, leading to inconsistent rendering and layout. Fixing these ensures predictable behavior across all environments and passes WCAG accessibility audits.
WarningFormat mode -- deeply nested HTML with mixed void elements
Input:
<form><fieldset><legend>Sign up</legend><label>Email<input type="email" name="email"><br></label><button type="submit">Submit</button></fieldset></form>
Output:
<form>
<fieldset>
<legend>Sign up</legend>
<label>Email
<input type="email" name="email">
<br>
</label>
<button type="submit">Submit</button>
</fieldset>
</form>
The formatter correctly identifies input and br as void elements that do not increase indentation, while properly nesting form, fieldset, label, and button. Notice that input inside a label does not close the label -- the formatter tracks nesting accurately. This formatted output is much easier to review for accessibility issues like missing aria labels or incorrect form structure.
FAQ
Frequently asked questions about HTML formatters, beautifiers, and minifiers
What does an HTML formatter do?
An HTML formatter takes unformatted, minified, or otherwise messy HTML code and restructures it with consistent indentation, line breaks, and spacing that reflects the nesting hierarchy of elements. This makes it immediately readable to humans, allowing developers to quickly understand parent-child relationships, identify where specific elements begin and end, spot mismatched or unclosed tags, and debug layout and rendering issues. Formatted HTML is also much easier to work with in version control systems like Git, where line-by-line diffs become meaningful rather than showing the entire file as a single changed line.
What is the difference between HTML formatting and HTML minification?
HTML formatting (also called beautifying) adds whitespace, indentation, and line breaks to make code more readable for developers. HTML minification does the opposite -- it removes all unnecessary whitespace, comments, and line breaks to produce the smallest possible file. Formatted HTML is used during development for readability and debugging. Minified HTML is used in production to reduce file size, improve page load speed, and lower bandwidth costs. A typical HTML file can be reduced by 15-30% through minification, and those savings compound when combined with gzip or Brotli compression on the web server.
Does HTML minification break my website?
For the vast majority of HTML, minification is completely safe. This tool removes comments and collapses whitespace between tags, which has no effect on how browsers render the page. There are two important exceptions where whitespace is semantically significant: content inside pre tags (where whitespace is displayed as-is for code blocks and preformatted text) and textarea elements (where initial whitespace becomes part of the input value). This formatter preserves content inside those tags unchanged. Inline elements like span and a can also be affected by whitespace collapsing in edge cases, but this is rarely a visual issue in practice.
What HTML errors can this validator detect?
This tool detects two categories of structural HTML errors: mismatched tags (where an opening tag is closed by a tag with a different name, for example opening a div but closing a span) and unclosed tags (where an opening tag has no corresponding closing tag anywhere in the document). These are the most common errors that can cause unexpected rendering behavior and break document structure. The validator correctly skips void elements like br, hr, img, input, and meta that do not require closing tags. For comprehensive HTML5 validation including attribute rules, deprecated element warnings, and accessibility requirements, the W3C Markup Validator is the authoritative tool.
Is my HTML code sent to a server when I use this tool?
No -- all formatting, minification, syntax highlighting, and validation run entirely in your browser using JavaScript. When you click Format, Minify, or Validate, the processing happens locally on your device and the results are displayed in the same page. Nothing is transmitted to any server, no data is logged, and no cookies are set by this tool. This makes it safe to paste confidential HTML including templates containing API keys, internal URL structures, or sensitive content. The tool is fully functional offline once the page has loaded.
How much does HTML minification reduce file size?
The reduction depends entirely on how much whitespace and how many comments the original HTML contains. A hand-authored HTML file with generous indentation might see 20-35% reduction. An already-compact HTML file might only see 5-10% reduction. When the minified HTML is then compressed by your web server using gzip (deflate) or Brotli compression, the total reduction from the original to the compressed-minified version is typically 70-85%. This is why minification and server-side compression are considered complementary -- minification removes redundant characters while compression exploits repetitive patterns.
What is HTML syntax highlighting and how does it work in this tool?
Syntax highlighting applies different colors to different parts of HTML code to make it easier to read at a glance. This tool highlights element names in orange, attribute names in purple, attribute values in green, and comments in grey -- a color scheme that mirrors popular code editors like VS Code. The highlighting is generated by parsing the formatted HTML output with a regular expression-based highlighter that replaces tag names, attribute patterns, and comment patterns with HTML span elements carrying CSS color classes. The highlighted output is rendered using dangerouslySetInnerHTML after the input has been sanitized through HTML entity encoding.
How do I format HTML that was generated by a CMS or template engine?
HTML generated by CMS platforms like WordPress, Drupal, or Shopify, or by template engines like Jinja2, Handlebars, or Liquid, is often delivered as a single long line with no indentation. Paste the raw HTML source from your browser's View Source or DevTools Elements panel directly into the Input field of this tool and click Format. The formatter will add indentation based on the tag nesting structure. Note that template-specific syntax like Jinja2 blocks, Handlebars helpers, or Liquid tags are treated as plain text by this formatter since they are not standard HTML -- the formatter focuses on the HTML element structure and ignores template-language syntax.
Should I format HTML before committing it to a Git repository?
Consistently formatted HTML makes a significant difference to Git workflow quality. When HTML is formatted with predictable indentation, each line in a diff corresponds to a meaningful unit of code, making pull request reviews much easier and code history more useful. If HTML is stored as a single long line, any change to the file shows the entire file as modified in the diff, making it impossible to see what actually changed. Many development teams use automated formatters like Prettier as a Git pre-commit hook to ensure all HTML is consistently formatted before it ever reaches the repository. This tool is useful for one-off formatting when automated tooling is not set up.
What is the best way to use the HTML formatter for SEO?
Well-structured, readable HTML contributes to SEO in several ways. Clean HTML with proper semantic structure (correct use of h1-h6, nav, main, article, aside, footer) helps search engine crawlers understand your page hierarchy. Removing unnecessary whitespace through minification reduces page weight, which contributes to faster load times -- a confirmed Google ranking factor. Properly formatted HTML also makes it easier to spot issues like duplicate heading tags, missing alt attributes on images, or incorrectly nested landmark elements that could affect crawlability and accessibility scoring. Use the formatter during development to maintain readable code, then use the minifier before deploying to production.
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