Minify HTML

No, and for source code that is the point. Nothing is uploaded and no request leaves your device. Pasting proprietary source into an online minifier that posts it to a server is a disclosure, whatever the site says about retention — and it is exactly the sort of thing that is done in a hurry without thinking.

Not the way it is set up here. Whitespace is only collapsed where it does not render: between block elements such as divs and list items. The space BETWEEN INLINE elements is kept, because removing it visibly joins two words together — "</span> <span>" is a real space on screen and "</span><span>" is not. The contents of <pre> and <textarea> are left byte for byte alone. And removing optional closing tags is deliberately switched off: it is valid HTML, but a good many template engines and email clients parse the result badly.

Comments, whitespace that never rendered, and the slack inside <style> and <script> blocks. Your markup structure, attributes and text are untouched — the tool is checked by parsing the page before and after and confirming the element count, the list items and the visible text are identical.

Only if the output is going straight to a browser. It is valid HTML and it saves a little, but unquoted attributes break some template engines, some email clients and most naive parsers. It is off by default and the page warns you when you switch it on.

Yes, both, using the same engines as our CSS and JavaScript minifiers. One exception: if your inline CSS uses native nesting or modern media queries, the CSS pass is switched off for that run — the CSS minifier predates those features and would silently delete rules. The HTML is still minified, and the page tells you that happened rather than handing back a page missing styles.

For hand-written HTML with indentation and comments, commonly 10–30%. Then gzip on your server does most of the remaining work — minifying first still helps, because the two compound, but do not expect minification alone to halve a file.

html-minifier-terser 7.2.0, which is MIT-licensed, served from this site rather than a CDN, and downloaded only when you open this page.