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CSS Minifier

Make stylesheets smaller. Paste CSS and minify it with CSSO, which removes whitespace and comments, shortens colours and values, and can safely merge duplicate rules and selectors — keeping /*! licence */ comments.

Paste your CSS and click Minify. CSSO parses the stylesheet and outputs the shortest equivalent CSS; with structural optimisation on, it also merges identical rules and removes overridden declarations. You'll see the original and minified sizes and can copy or download the result.

Uses CSSO, which removes whitespace and comments, shortens colours and values, and (optionally) merges rules — without changing how the CSS behaves. Everything runs in your browser.

Zero Server Uploads

Files process in local RAM

Instant WASM Speed

No waiting queues or lags

Unlimited Batching

Convert files without limits

Suggest a Feature or Improvement for CSS Minifier

Need custom options, higher limits, or extra format support? Let our engineering team know!

How to use CSS Minifier

  1. 1Paste your CSS.
  2. 2Keep structural optimisation on for the smallest output.
  3. 3Click Minify CSS.
  4. 4Copy or download styles.min.css.

Why minify CSS

CSS is render-blocking: the browser can't paint the page until it's downloaded and parsed. Smaller CSS means a faster First Contentful Paint, especially on mobile. Minify and serve it with Brotli or gzip compression.

Removing unused CSS usually saves even more than minifying — check your page's opportunities with the Page Speed Checker.

Readable again

Need to read minified CSS? Format it with the CSS Beautifier. For JavaScript, use the JavaScript Minifier.

Frequently Asked Questions

Is structural optimisation safe?

CSSO only merges rules when the result is equivalent. If you rely on specific rule order across selectors with hacks, turn it off.

Is my code or data uploaded?

No. Everything runs in your browser; nothing you paste is sent to a server or stored.

Related Tools

JavaScript Minifier

Minify JavaScript with Terser — shorten names, drop console calls and see the size saved.

CSS Beautifier

Format minified CSS into clean, indented, one-declaration-per-line stylesheets.

Page Speed Checker

Test any page's speed on mobile and desktop with Google Lighthouse — scores, metrics and what to fix.