CSS Minifier

CSS Minifier walks the stylesheet one character at a time, dropping comments and every space, tab and newline that cannot change how a rule is read. It is conservative on purpose: nothing is renamed, no two selectors sharing a body are merged, no declaration is reordered, and nothing is deleted for being overridden further down the file. Combinators are tightened, so a > b loses its spaces, and the final semicolon of each block goes with them.

The scanner knows where it has to stop. Quoted strings are copied through untouched, so a content value keeps both its spacing and any text inside it that looks like a comment. Inside a bracket the rule relaxes: a space survives unless it follows an opening bracket or a colon, sits beside a comma, or comes just before the closing bracket — which is what leaves calc(100% - 24px) intact while (min-width: 600px) still loses the space after its colon. A space written before a colon is also kept, because that is exactly what separates the descendant selector p :first-child from a pseudo-class attached to p. Two checkboxes control the rest: licence comments, meaning any comment opening with an exclamation mark or a second asterisk, are preserved while that option is on, and the colour option shortens #aabbcc to #abc only where all three pairs repeat, leaving eight-digit hex with an alpha channel alone.

It is a scanner rather than a CSS parser, and that sets the boundary of what it can be trusted with. Nothing is validated: a stray brace or a misspelt property travels straight through, and an unclosed comment discards everything after it, because the scanner looks for the closing marker and reaches the end of the file instead. A url() is copied through rather than picked apart, although runs of whitespace inside it collapse to one and the spaces beside its brackets go; that protection stops at the first closing bracket, so a path carrying an unescaped bracket of its own hands the remainder of the value back to the ordinary rules. An unclosed bracket reaches further still, because the scanner then treats everything after it as bracket contents and keeps spaces it would otherwise remove. Check the result against a real page before you ship it.

The byte counter measures the file, not the transfer. Almost everything removed here — indentation, blank lines, comment blocks — is what gzip and brotli are already best at, so a stylesheet served compressed gains far less on the wire than the percentage suggests. The saving is real where the CSS is counted uncompressed: inside a style block in the document head, in an email, or against a bundle budget. All of it happens in this browser tab, so the stylesheet is not uploaded — though that also means there is no file picker and no .css download, only a box to paste into and a button to copy from.

Runs on your device. Your file is processed directly in this browser.