Compare CSS Online
Paste two stylesheets below and find differences instantly.
About CSS Compare Online
Compare two CSS files or stylesheets. Our css file compare online tool finds differences in styles, selectors, and properties. The best css diff checker available free. All processing happens in your browser — nothing is uploaded to any server. Completely free, no sign-up required.
CSS stylesheets control the visual presentation of every website, and even minor changes to selectors, properties, or values can have cascading effects across an entire application. Our CSS comparison tool helps front-end developers, designers, and DevOps teams quickly identify what changed between two versions of a stylesheet. Whether you are comparing CSS before and after a build process, reviewing pull request changes to your design system, tracking down a visual regression caused by a specificity conflict, or auditing the output of CSS preprocessors like Sass or Less, this tool delivers instant, clear results.
Modern CSS is increasingly complex — with custom properties (CSS variables), container queries, cascade layers (@layer), nesting, grid and flexbox layouts, and extensive media queries for responsive design. Manually reviewing changes across large stylesheets with hundreds of selectors is impractical and error-prone. Our diff tool highlights every modification including changed property values, added or removed selectors, reordered rules, modified media query breakpoints, updated animation keyframes, and altered custom property definitions. The color-coded output makes it effortless to review changes, whether you are working with component-scoped styles, utility-first frameworks like Tailwind output, or traditional global stylesheets.
Pro tips for effective CSS comparison: if you are comparing minified CSS, run it through a formatter first (tools like Prettier or css-beautify) to get one property per line for granular diffs. When comparing CSS from different preprocessor compilations, normalize vendor prefixes and sort properties alphabetically in both versions. For large design systems, consider comparing individual component stylesheets rather than the entire concatenated bundle. All processing is done locally in your browser — your proprietary design tokens, brand styles, and client project CSS never leave your machine.
Frequently Asked Questions
Can I compare minified CSS with this tool?
Yes, you can paste minified CSS directly into the tool and it will show differences. However, since minified CSS is typically on one or very few lines, the diff output will show large blocks as changed rather than individual properties. For the most useful comparison results, we recommend running both CSS files through a formatter (like Prettier or CSSBeautifier) to expand them to one property per line before comparing. This gives you granular, property-level diffs.
How does the tool handle CSS selector specificity differences?
The tool compares CSS as text, so it will highlight any change in selector syntax — whether that is a class being changed to an ID, a new pseudo-class being added, or a combinator being modified. While it does not calculate specificity scores, it clearly shows you which selectors were modified, making it easy to identify potential specificity conflicts that could cause visual regressions in your stylesheets.
Can I compare Sass/LESS source files or only compiled CSS?
You can compare any text content, including Sass (.scss/.sass) and LESS source files. The tool performs a text-based diff, so it works with preprocessor syntax including variables, mixins, nesting, and functions. You can also compare compiled CSS output to verify that your preprocessor changes produce the expected results. It is a versatile tool for any stage of your CSS workflow.
What CSS changes are most commonly caught with this tool?
Common changes detected include modified color values, updated font sizes and families, changed spacing (margin/padding), added or removed selectors, altered media query breakpoints, new or deleted CSS custom properties (variables), modified z-index values, updated flexbox/grid properties, changed animation timings, and removed vendor prefixes. The tool catches any textual difference, no matter how small — even a single changed pixel value.
Is this tool useful for comparing CSS framework updates?
Absolutely. When upgrading CSS frameworks like Bootstrap, Tailwind, or Material UI, comparing the old and new CSS output helps you understand exactly what styles changed. This is critical for identifying potential breaking changes, deprecated utilities, renamed classes, or modified default values. Paste the relevant portions of the framework CSS from each version to see precisely what was added, removed, or modified in the upgrade.