CSS Formatter / Minifier

Formatting CSS is a whitespace transformation, with one important exception: order within a rule is meaningful. Later declarations override earlier ones of the same property, so a formatter that sorted properties alphabetically would silently change which value wins. This tool reorders nothing. It normalises indentation, spacing around braces and colons, and line breaks between rules: the things that make a stylesheet readable without altering what the browser computes.

Minification is the same transformation aimed the other way: strip every byte that does not change behaviour. Whitespace between tokens goes, the last semicolon in a block goes, comments go. What must survive is anything inside a string or a url() (whitespace there is data, not formatting) and any comment marked as legally required. Over-aggressive minification that ignores those cases produces a stylesheet that is smaller and broken, usually in a way that only shows up on one page.

Because formatting requires parsing, the formatter doubles as a syntax check. A missing closing brace, an unterminated string or a stray character typically produces output that stops or goes visibly wrong at the point of the problem, which is often faster than hunting for it by eye. What it cannot tell you is whether a property name is real or a value is valid for it: `colour: red` is syntactically perfect CSS and does nothing at all. For that, a linter such as stylelint is the right tool; this one answers the structural question.