Definition
CSS/JS minification involves reducing file sizes by removing whitespace, line breaks, comments, and shortening variable names. This process does not affect code functionality but significantly reduces file weight, with a CSS file potentially losing 30-60% of its size after minification. Common tools include Terser and UglifyJS for JavaScript, and cssnano and clean-css for stylesheets. Minification is often combined with server-side Gzip or Brotli compression to maximize bandwidth reduction. In modern workflows, minification is automated via bundlers like Webpack, Rollup, or Vite. For SEO, minification directly contributes to improved load times and Core Web Vitals.
Key Points
- Can reduce file sizes by 30-60%
- Does not affect code functionality
- Popular tools: Terser (JS), cssnano (CSS), Webpack, Vite
Practical Examples
CSS weight reduction
A 250 KB main.css file is reduced to 95 KB after minification, a 62% reduction.
JavaScript bundle
Five JS files totaling 800 KB are concatenated and minified into a single 210 KB file with Terser.
Frequently Asked Questions
Minification removes unnecessary characters from source code. Gzip/Brotli compresses binary data server-side. The two are complementary.
Yes, keep files readable in development and deploy minified versions in production. Webpack and Vite automate this.
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Last updated: 2026-02-07