What it leaves alone
Whitespace inside <pre> and <textarea> is content, not layout — re-indenting it changes what the page shows, so those are handed back exactly as they arrived. Everything inside <style> and <script> is formatted with the CSS and JavaScript formatters rather than treated as markup.
Void elements do not open a level, so an <img> in the middle of a block does not push the rest of it sideways.
Indenting is not always harmless
Whitespace between inline elements is a word break. Moving <span> tags onto their own lines can add or remove a space in the rendered text, which is why this is a reading tool rather than something to run over production markup.
If you need the rendering byte-identical, use the minifier instead — it collapses runs to a single space rather than introducing new ones.
Frequently asked questions
Is my markup uploaded anywhere?
No. The markup is parsed and re-indented in the page. Everything happens in the tab, so an unpublished template stays private.
Will indenting change how the page looks?
It can, very slightly. Whitespace between inline elements is a word break, and moving tags onto their own lines adds or removes those gaps. Use the minifier if you need the rendering byte-identical.
Does it format inline CSS and JavaScript?
Yes — anything inside a style or script tag goes through the matching formatter rather than being treated as markup.
What happens to pre and textarea?
They are handed back exactly as they arrived. The whitespace in them is content, and re-indenting it would change what the page shows.
Something wrong with this tool, or an idea for it? Tell us