CSS Compressor (Advanced)

Advanced CSS compression goes beyond basic whitespace and comment removal to apply structural optimizations that reduce CSS file size at the rule and declaration level. Our CSS compressor (advanced) runs four passes over your stylesheet: first removing whitespace, comments, and redundant semicolons; then merging duplicate selectors that appear multiple times in the file; then removing vendor-prefixed properties where the unprefixed standard version is also present; and finally collapsing longhand properties (like margin-top/right/bottom/left) into their shorthand equivalents (margin). All processing runs entirely in your browser — no server, no upload, complete privacy.

1. 1Paste or upload your CSS: Enter any CSS in the input panel or upload a .css file. The tool accepts any valid CSS including media queries, keyframes, and custom properties.
2. 2Instant browser-based multi-pass compression:Click "Compress CSS". Four optimization passes run locally in your browser — no data is sent to any server. The stats panel shows exactly how many optimizations each pass applied.
3. 3Copy or download the compressed CSS: Copy the output to clipboard or download as a .css file. The output is valid, production-ready CSS that can be used directly in any web project.

• Whitespace & Comments: All whitespace between tokens is collapsed, comments are stripped, redundant semicolons before closing braces are removed, and zero values lose their units (0px → 0).
• Duplicate Selector Merging: When the same selector appears multiple times, all its declarations are merged into a single rule — later declarations win (preserving cascade order). Empty rules after merging are dropped.
• Vendor Prefix Removal: Vendor-prefixed properties (-webkit-, -moz-, -ms-, -o-) are removed when the unprefixed standard property is also present in the same rule — covering flexbox, transforms, transitions, animations, border-radius, and more.
• Shorthand Collapsing: When all four longhands of margin, padding, border-radius, border-width, or border-color are present, they are collapsed into the shorthand with optimal value repetition (e.g. 16px 16px 16px 16px → 16px).

The advanced CSS compressor uses a structural parser, not a full CSS specification parser. It handles standard rule sets and at-rules correctly, but complex nested CSS (CSS Nesting Level 3), SCSS/Less syntax, and CSS custom property declarations with var() in shorthand values are kept verbatim without shorthand collapsing. Vendor prefix removal only applies when the exact unprefixed property is present in the same rule — it never removes a prefixed property that has no unprefixed counterpart. Always test compressed output in your target browsers before deploying to production.