Beautify messy HTML, minify for production, view with line numbers, or validate for unclosed tags. Everything runs in your browser — no upload, no signup.
Why this matters
HTML is forgiving — browsers will render almost anything you throw at them. That's also why it's easy to ship broken markup: unclosed <div>s that subtly shift your layout, duplicate id attributes that break your JS, or whitespace from copy-pasted snippets that bloats your page. Most "weird CSS bug" reports trace back to malformed HTML.
This formatter parses your HTML with the browser's built-in DOM parser, then re-serializes it with consistent indentation and line breaks. The minifier does the opposite — strips optional whitespace for production. The validator catches the structural mistakes (unclosed tags, duplicate IDs, missing alt attributes) before they ship. Everything happens locally — your markup never leaves the browser.
Best uses: formatting DevTools-copied HTML for editing, minifying production HTML to shave kilobytes, validating email templates before sending, checking accessibility issues like missing alt text, and tidying up AI-generated HTML that usually arrives as a single unindented wall.
Input HTML
Output
Validation Results
Why Format HTML?
HTML copied from browser DevTools, generated by templates, or written under time pressure often arrives as a single unindented wall of tags. Formatting it makes the structure visible at a glance: which elements nest inside which, where each block starts and ends, and how the document is organized. This dramatically speeds up debugging, code review, and modifications.
When to Minify
Minification is the opposite trade-off: smaller files at the cost of readability. Production HTML sent to browsers should usually be minified — a 25% size reduction is typical. Email templates, single-page apps, and AMP pages especially benefit. Keep your source formatted and use a build step to generate the minified version.
Common HTML Mistakes
The validator catches the mistakes that cause real bugs: unclosed <div> tags that break layout, mismatched pairs like <span> wrapping a block element, duplicate id attributes that break JavaScript selectors, and missing alt attributes on images. These issues are hard to spot by eye but easy for a parser to detect.
About the View Source Mode
View Source adds line numbers and shows the original code in a monospace, easy-to-read format — useful for sharing snippets, citing specific lines, or comparing versions. It does not execute or render the HTML; it just presents it for reading.
Frequently Asked Questions
What does the HTML formatter do?
The HTML formatter takes messy, minified, or unindented HTML and adds proper indentation, line breaks, and consistent formatting. It uses the browser's built-in HTML parser to read the structure, then re-serializes the code with each element on its own line and nested elements indented.
When should I minify HTML?
Minify HTML for production deployments where every kilobyte matters: high-traffic websites, mobile-first pages, email templates, and any page where load time directly affects user experience. Minification removes unnecessary whitespace, comments, and optional tags, typically reducing file size by 20-30%.
How does the validator work?
The validator parses your HTML and reports common issues: unclosed tags, mismatched opening and closing tags, duplicate ID attributes, and structural problems. It catches the 90% of mistakes developers actually make, especially useful for HTML written by hand or generated by templates.
Are my HTML files uploaded?
No. All formatting, minification, and validation happens entirely in your browser using JavaScript. The HTML is never sent to any server, never logged, and never stored. Open your browser's network tab to verify — no requests leave your device.
Does the formatter change my code?
The formatter preserves your code's structure and content — it only changes whitespace, line breaks, and indentation. The parsed output is identical. The minifier changes the code more substantially by removing optional tags, comments, and whitespace, which can make debugging harder. Keep your formatted source in version control and only deploy the minified version to production.
