Gzip vs Brotli: Compression Ratio, Speed, and Web Performance

Brotli produces 15-25% smaller files than Gzip for text-based web assets (HTML, CSS, JavaScript, SVG, JSON). It was developed by Google specifically for HTTP compression. Gzip is older, faster at compression, and universally supported. Both are supported by all modern browsers. Use Brotli for static assets when you can pre-compress. Use Gzip when compression speed matters or as a fallback.

Compression Ratio

Brotli consistently beats Gzip on text content. At maximum settings, Brotli achieves 15-25% smaller output than Gzip on typical web assets. The gains come from Brotli using a built-in dictionary of common web strings (HTML tags, CSS properties, JavaScript keywords) and a more advanced entropy coding algorithm. For binary data like images or already-compressed files, the difference is negligible. The savings matter most for the assets that make up web page loads: HTML, CSS, JS, and fonts.

Compression Speed

Gzip at its default level (6) compresses significantly faster than Brotli at equivalent quality. At maximum compression, Brotli can be 10-50x slower than Gzip. This makes Brotli impractical for on-the-fly dynamic compression at high levels. In practice, servers run Brotli at level 4-6 for dynamic content, which brings speed close to Gzip while still delivering smaller files. For static assets, you pre-compress at level 11 during build time, so speed does not matter. Decompression speed is nearly identical for both.

Browser and Server Support

All modern browsers support both Gzip and Brotli. Brotli has 97%+ global browser support. The only catch: Brotli requires HTTPS. Browsers will not accept Brotli-compressed responses over plain HTTP. Gzip works over both HTTP and HTTPS. On the server side, Nginx, Apache, Caddy, and all major CDNs (Cloudflare, Fastly, AWS CloudFront) support Brotli. Most CDNs apply Brotli automatically for supported clients and fall back to Gzip for the rest.

When to Use Each

For static assets (CSS, JS, fonts, SVG), pre-compress with Brotli at level 11 during your build process. This gives maximum compression with zero runtime cost. For dynamic content (API responses, server-rendered HTML), use Brotli at level 4-6 or stick with Gzip if latency is critical. Always serve Gzip as a fallback for clients that do not support Brotli. For general-purpose file compression outside the web, Zstandard (zstd) outperforms both and is worth considering. If you need to compare other compression formats, see our Bzip2 vs Gzip comparison. To compress and archive files for sharing, try our ZIP Files tool.