Minify & Compress CSS Online
Paste your CSS. Get a minified copy back. Removes whitespace, comments, and redundant declarations — typically a 30–70% size reduction. Runs entirely client-side. No upload, no server, no account required.
About this tool
Why minify CSS in the first place?
CSS minification and page performance
Every kilobyte of CSS your browser has to download and parse delays the first paint. CSS is also render-blocking — the browser refuses to paint anything until it has finished parsing the entire stylesheet. That makes it one of the most important assets to keep small.
A typical hand-written stylesheet contains 30–70% redundant characters: comments, indentation, blank lines, trailing semicolons. Minification strips all of them. The browser parses and applies the minified version exactly the same way, just faster.
How much bandwidth does CSS compression actually save?
On a 200KB stylesheet, a 40% reduction saves 80KB on every page load. Multiply that by gzip or Brotli compression on your server (which compounds with minification, not duplicates it) and you typically land at a 4–6× total size reduction over the raw uncompressed file.
On mobile networks where every round trip costs hundreds of
milliseconds, that translates directly to a better
LCP and a better Core Web Vitals score.
Minifying CSS without breaking your styles
A safe minifier only removes characters that don't affect how the CSS parses. It does not reorder rules, merge selectors, or drop declarations it thinks are unused — those optimizations need a full CSS parser and access to your HTML.
This tool keeps it conservative on purpose. For deeper optimization (dead-code elimination, unused-rule pruning, vendor-prefix cleanup) use a build-time tool like cssnano or PurgeCSS. Or skip the toolchain and let us write your CSS from scratch — see our Design to HTML service.
FROM THE TEAM THAT BUILT THIS TOOL
We write CSS like this by default.
Every MarkupFox HTML delivery ships with a purged, minified CSS build. No dead classes, no unused rules, no leftover utilities. Production-ready, the moment it lands in your inbox.
Clean up minified or AI-generated HTML. Configurable indentation.
Convert pixel values with a Tailwind spacing reference alongside.
Drag and drop. Get a data URI for inline embedding.
SEO + Open Graph + Twitter Card with live SERP preview.
WCAG AA/AAA contrast ratio for any two colors, with a live preview.
Frequently asked questions
What is CSS minification?
Minification removes all unnecessary characters from CSS — whitespace, comments, and newlines — without changing how it functions. The result loads faster because the file is smaller.
Does my CSS leave my browser?
No. This tool runs entirely in your browser using JavaScript. Your CSS is never uploaded to any server — it's processed locally and privately.
How much does CSS minification reduce file size?
Typical reductions are 30–70%, depending on how much whitespace and how many comments are in the original. Combined with gzip or Brotli compression on the server, savings compound further.
What does "Shorten 0px → 0" mean?
In CSS, a zero value needs no unit — 0px and 0 are identical. Stripping the unit saves a few bytes per occurrence across a large stylesheet.
Will minification break my CSS?
No, provided the input CSS is valid. This minifier only removes safe characters and applies well-known optimizations like lowercasing hex colors and shortening zero values. It does not reorder rules, drop selectors, or change specificity.
Should I minify CSS by hand or use a build tool?
Build tools (Vite, webpack, Parcel, esbuild) minify CSS automatically as part of your production build. This tool is best for one-off optimizations — email templates, landing pages outside your main build, or quick A/B tests.