CSS Minifier
Only safe rewrites: comments, whitespace and redundant semicolons go; colours and decimals get shorter. Selectors, values, escape sequences and url() are carried through untouched — nothing is renamed or restructured, so the output always behaves like the input.
About CSS Minifier
Strips comments, indentation and redundant whitespace from CSS, and shortens #ffffff to #fff and 0.5 to .5. The line under the output tells you the original size, the minified size and the percentage saved.
The point is transfer size, not readability. A stylesheet with comments and indentation is often about a third whitespace and comments; removing that makes the file smaller and marginally cheaper to parse.
This is not the same thing as gzip — do both. Minifying removes redundant characters from the file; gzip/brotli compresses again in transit. CSS is highly repetitive, so gzip typically takes another 60–70% off the minified file. Serving the minified file without gzip leaves most of the win on the table.
Only safe rewrites — that is the boundary here. Comments, whitespace, the last semicolon of a block, long colour notation and leading zeros in decimals. It does not rename anything, merge duplicate rules, reorder selectors, or touch 0px. That last one is deliberate: in calc(100% - 0px) dropping the unit turns "percentage minus length" into "percentage minus number" and the declaration becomes invalid. Some online minifiers do that substitution and break calc.
Three things pass through untouched: quoted strings (content: "a; b }"), url(...) (only the padding inside the parentheses is trimmed), and backslash escapes such as \9 or \31 — including the space that terminates the escape.
SCSS/LESS nesting will not crash it, since it is treated as text, but nothing is compiled. Use a real build step for that.
Everything runs in the browser; the stylesheet is never uploaded.
Frequently asked questions
The file barely got smaller?
It was probably minified already, or most of the weight is base64 images and fonts. Only whitespace and comments can be removed from the text.
Will minifying change how the page looks?
No. Only whitespace, comments and redundant semicolons are removed; selectors and values are untouched, and 0px is never rewritten to 0.
Should I still enable gzip?
Yes. Minifying removes characters from the file; gzip compresses in transit. You want both.
Why not turn 0px into 0?
In calc(100% - 0px) dropping the unit invalidates the declaration, so that substitution is deliberately skipped.
Are legacy hacks like *zoom and _height kept?
Yes. They are just characters to the minifier — recognised and preserved, never rewritten.
Is my stylesheet uploaded?
No, minification runs entirely in the browser.
