About the Stylus to CSS Converter
Teams reach for this page when they are leaving Stylus behind. An old project may still carry a handful of .styl files whose build tooling no longer installs cleanly, and the fastest way out is to produce the CSS they were generating and commit that instead. Everything the preprocessor was doing gets resolved: names are replaced by their values, mixin bodies are inlined wherever they were called, and each nested rule is expanded into a full selector path.
Reading the result tells you how much the preprocessor was really buying you. Nesting three levels deep produces long descendant selectors that are slower to match and harder to override, and a mixin used in twenty places duplicates its declarations twenty times. Both are usually worth cleaning up by hand before the flattened file becomes your source of truth. Custom properties are a good replacement for the variables you are losing, since they cascade and can be changed at runtime.
Two practical notes. Comments written with two slashes never appear in the output, because the preprocessor treats them as private, while /* */ comments are preserved; move any licence header into the block form before converting. Media queries stay nested inside their at-rule and keep the rules they wrapped. If you would rather move sideways to another preprocessor than abandon one entirely, Stylus to SCSS and Stylus to LESS keep your variables and mixins as source.
How to use
- Paste the contents of a .styl file into the left pane.
- Leave the output expanded so you can read the flattened selectors, then switch to compressed once you are happy.
- Look for deeply nested selectors and repeated mixin output, and simplify them before committing.
- Download the file as .css and remove the preprocessor from your build.
Common questions
- Will my variables become custom properties?
- No, they are substituted with their values. Declare custom properties on :root by hand if you want the values to stay adjustable at runtime.
- Why did my two slash comments disappear?
- Those are silent comments and never reach the compiled stylesheet. Rewrite anything you need to keep, such as a licence header, as a block comment.
- Does the converted file behave identically in the browser?
- For everything this page can compile, yes. Declaration order and specificity are preserved, so the cascade resolves exactly as it did before.
- How do I keep the file readable afterwards?
- Run it through a beautifier and split it into partials by component, since a flattened stylesheet loses the grouping that nesting used to provide.