Make messy HTML readable
Minified HTML, page source copied from a browser or code exported by a website builder is hard to read. The formatter indents each nested element so you can see the structure at a glance, and it formats CSS inside <style> tags and JavaScript inside <script> tags too.
Spaces or tabs?
Two spaces is the most common style for HTML because pages nest deeply. Four spaces or tabs are fine if your team uses them; consistency matters more than the choice.
Line wrapping
Turning on wrapping breaks very long lines, such as tags with many attributes, so you don't have to scroll sideways. Leave it off if you plan to compare files line by line.
Will formatting break my page?
Formatting changes only whitespace between tags. In rare cases whitespace matters, for example inside <pre> blocks or between inline elements where a space appears between words, and the formatter keeps <pre> content as it is. Always test a page after replacing code.
Related tools
Make your stylesheets smaller with the CSS Minifier and your scripts with the JavaScript Minifier. Need SEO tags for the page head? Use the Meta Tag Generator.