Paste CSS, load a sample, or upload a .css file. Validate and beautify it for easier editing, or minify it for delivery, then compare exact sizes and export the result without uploading your stylesheet.
.css file./*! MIT */
.card {
color: #ffffff;
margin: 0px 16px;
}/*! MIT */.card{color:#fff;margin:0 16px}Whitespace is removed, zero units and colours can be shortened, and the exclamation comment is retained when that option is enabled.
@media(min-width:48rem){.card,.panel{display:grid;gap:1rem}}@media (min-width: 48rem) {
.card,
.panel {
display: grid;
gap: 1rem;
}
}Indentation and line breaks are added while the at-rule, selector list, declarations, and values remain CSS.
A CSS minifier parses a stylesheet, removes comments and optional whitespace, shortens compatible values, and prints fewer bytes. Safe mode disables cross-rule restructuring. Optimized mode can also merge or reorganize compatible rules. Neither mode removes selectors based on the HTML that uses them.
Formatting is for reading, reviewing, and editing. It adds consistent indentation and line breaks but does not reconstruct an author's exact source. Minification is for delivery. Keep a readable source file in version control and treat minified CSS as a generated artifact.
Fewer bytes can reduce transfer and parse work, especially across many visits or on slower connections. Web servers and CDNs should also apply gzip or Brotli. Transport compression and minification complement each other: one encodes repeated bytes, while the other removes or simplifies source characters.
CSS behavior depends on selector specificity, source order, layers, inheritance, custom properties, and browser support. Optimizers are designed to preserve behavior, but legacy hacks, unusual vendor syntax, and deliberately repeated fallbacks deserve visual regression testing.
Use PostCSS, Lightning CSS, CSSO, clean-css, or a bundler integration when you need repeatable builds, source maps, prefixing, nesting transforms, imported files, asset rewriting, or automated tests. A browser tool is most useful for snippets, one-off files, and inspecting compact CSS.
Parsing confirms that the processing engine can understand the stylesheet; it is not a complete standards or browser-compatibility audit. Unknown property names and many unknown values are valid CSS grammar, while support differs by browser. Use browser developer tools and compatibility data for deployment decisions.
Formatting adds consistent indentation, spacing, and line breaks for people to read. Minification removes unnecessary bytes and may optimize equivalent CSS for delivery. Formatting normally increases file size; minification normally reduces it.
No. CSS is sent only to a Web Worker inside the current browser tab. Starlight Tools does not upload it or save it in local storage. The page downloads its open-source processing engines from CDNs, but stylesheet content is not included in those requests.
No. A beautifier can restore readable whitespace and indentation, but it cannot recover removed comments, the author's original formatting, or transformations made by an optimizer. Keep the source stylesheet in version control.
It is intended to preserve CSS behavior, but an optimized preset may combine or restructure compatible rules. Cascade order, browser quirks, unsupported syntax, and build-time conventions can matter, so test the exact output before deployment.
No. This page accepts standard CSS. Compile Sass, SCSS, or Less first. CSS Modules selectors may parse as CSS in some cases, but module-specific build behavior is outside this tool.
Yes. Enable Preserve exclamation comments to retain comments beginning with /*!, a common convention for licence notices. Review the result because a project's licence obligations can require other text or files.
Use a repeatable build pipeline for production projects with multiple files, source maps, PostCSS plugins, preprocessors, automated testing, or browser-specific transformations. This online tool is best for snippets, one-off files, and quick comparisons.