Before building our CSS minifier/formatter, we checked a popular tool directly and looked into two specific correctness risks in this category.
A sorting feature that can quietly break your CSS
Some CSS formatters offer an A-Z or "Idiomatic" declaration sort. Documentation around this feature admits it's "safe in the vast majority of cases but should be reviewed if your code relies on the cascade order of duplicate properties" — in plain terms, if you have the same property listed twice in a rule (a common fallback pattern, like a plain color followed by a gradient for browsers that support it), reordering can flip which one wins. This tool never reorders anything, full stop — there's no sort feature to accidentally reach for.
License comments, kept on purpose
Comments starting with /*! are a real, established convention — tools like YUI Compressor and CSSO specifically preserve them through minification because they usually carry license or copyright text that has to survive. A minifier that strips every comment indiscriminately can quietly remove attribution it was never supposed to touch. We tested this directly: a /*! MIT License */ comment survives minification here, while an ordinary /* internal note */ comment gets removed as expected.
Live, with a number you can act on
We checked toptal.com's CSS minifier directly — it requires clicking "Minify" for every change. This tool updates the instant you type, and shows exactly what you saved: original bytes, minified bytes, and the percentage reduction, not just a transformed textarea with no measurement attached.
