Indent messy HTML so it is easy to read, or minify it to a single line.
Each tag and each run of text goes on its own line, indented one step deeper inside every element that isn't closed yet. Void elements such as br, img, input and meta don't add indentation, comments and doctype stay where they are, and a stray closing tag can't throw the indentation off.
The contents of pre, textarea, script and style blocks are kept exactly as written, because whitespace inside them matters; squashing a script onto one line can turn the rest of it into a comment.
Minify removes HTML comments and turns runs of spaces, tabs and line breaks into single spaces. Whitespace between tags is reduced to one space rather than deleted, because between inline elements like links and bold text it's visible on the page. That makes the output a little larger than aggressive minifiers produce, but it never changes how the page looks.
Formatting adds line breaks and indentation, which browsers treat as spaces. In rare layouts that depend on no space between inline elements, check the result.
No. Script and style blocks are kept exactly as they are.
No, it's a formatter, not a validator. Use the W3C validator to check markup.
No. Formatting happens in your browser.
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