CSS Minifier

What is CSS minification?

CSS minification removes every byte the browser doesn’t need — comments, indentation, line breaks, the last semicolon in each rule — and rewrites some values into shorter equivalents. The resulting stylesheet is functionally identical but smaller, so it downloads and parses faster. Because CSS is render-blocking, a smaller stylesheet can directly improve First Contentful Paint and Largest Contentful Paint.

What this minifier changes

Why it is safe

Aggressive minifiers sometimes break stylesheets. This one only applies transformations that can’t change behaviour:

• Strings, url() values and escaped characters are protected and never modified.
• Units are only dropped on lengths — 0s, 0deg and 0% keep theirs (transition: 0s and keyframe selectors need them), and nothing inside calc(), min() or clamp() is touched because calc(0 + 10px) is invalid.
• The flex shorthand is skipped (flex: 1 1 0px and flex: 1 1 0 are not always equal in older engines), and custom property values only lose redundant spaces.
• Whitespace in selectors is kept where it means something: a :hover (any hovered descendant) differs from a:hover.
• @layer name {} is kept even when empty, because it declares layer order. License comments starting with /*! are preserved by default.

Minification vs. compression

Minifying and gzip/Brotli compression stack. Compression removes repetition; minification removes bytes compression can’t, such as comments. The Gzipped output figure shows roughly what will travel over the network if your server compresses responses (most do). For the biggest win, also remove unused rules with a tool like PurgeCSS, and inline only the critical CSS for above-the-fold content.

Want to inspect a minified file? Use Beautify mode here or the CSS Formatter. Checking a whole page’s performance? Run a page speed test.

Tools that pair well with the CSS Minifier

• HTML Formatter — Paste minified or messy markup and get clean, consistently indented HTML — including embedded <style> and <script> blocks.
• JavaScript Formatter — Unminify and pretty-print JavaScript, JSON or JSX with your preferred indentation and brace style — or strip whitespace and comments with a verified minifier.
• Image Compressor — Shrink photos and graphics by 50–90% without visible quality loss.
• SQL Formatter — Paste a query — or a whole migration — and get readable SQL with one clause per line, aligned joins and consistent keyword case, using the grammar of your database.