What is CSS Minifier?
The CSS Minifier is a tool that compresses your CSS stylesheets by removing unnecessary whitespace, line breaks, comments, and redundant syntax without changing the visual output of your styles. Modern websites rely on CSS for layout, animation, and responsiveness, and stylesheet sizes can grow rapidly as features are added. Every kilobyte of CSS that must be downloaded delays the time to First Contentful Paint, especially on slower connections and mobile devices. This minifier applies safe transformations including collapsing whitespace, removing the last semicolon in declaration blocks, shortening color values (e.g., #ffffff to #fff), and merging duplicate selectors, producing the smallest possible CSS while maintaining full browser compatibility.
Why Use CSS Minifier?
While build tools like Webpack and PostCSS can minify CSS as part of a pipeline, there are many situations where a standalone minifier is invaluable. Quick prototyping, debugging production stylesheets, preparing inline <style> blocks, or compressing CSS from third-party libraries that ship unminified all benefit from an instant, no-setup tool. Our minifier also shows you a before-and-after size comparison so you can quantify the savings. For performance-critical projects, reducing CSS size by even a few kilobytes can meaningfully improve Core Web Vitals scores, directly influencing search engine rankings and user experience.
How to Use
Paste your CSS code into the input editor or upload a .css file. Click 'Minify' to compress the stylesheet. The output panel shows the minified CSS alongside a summary of the size reduction (original bytes, minified bytes, and percentage saved). You can toggle options like removing comments only, preserving specific comments (e.g., license headers marked with /*! */), or enabling aggressive optimizations like merging media queries and removing unused vendor prefixes. Copy the result or download it as a .min.css file.
Example Usage
You have a stylesheet with 500 lines of development CSS including block comments, verbose formatting, and repeated vendor prefixes. Pasting it into the minifier produces a single-line output that is 40% smaller. The summary shows: Original: 12,450 bytes → Minified: 7,470 bytes (40% reduction). For an inline <style> block in an HTML email, this reduction can mean the difference between the email being clipped by Gmail (which truncates HTML over 102 KB) and rendering fully.
Benefits
Measurable file size reduction directly improves page load speed. Preserving license comments ensures legal compliance while still compressing aggressively. The visual size comparison makes it easy to justify optimization efforts to stakeholders. No build-tool configuration required — paste, minify, and copy. Supports modern CSS features including custom properties, nesting, container queries, and @layer rules.