Gzip Compression

Why It Matters

• Smaller transfers mean faster pages. A 200KB CSS file compressed to 40KB downloads five times faster on the same connection. Multiply that across all your text-based assets and the savings are substantial.
• Mobile users benefit the most. On slower mobile connections, every kilobyte counts. Gzip compression can turn a multi-second download into a fraction-of-a-second one, dramatically improving the mobile experience.
• It costs almost nothing on the server. Modern servers can compress files on the fly with negligible CPU overhead. The tiny processing cost is vastly outweighed by the bandwidth savings and speed improvements.
• Search engines expect it. Uncompressed text delivery is flagged as a performance problem by most site analysis tools. Enabling gzip is considered a baseline best practice for web performance.

How to Enable It

1. Enable it in your web server configuration. For Apache, add mod_deflate directives to your .htaccess file. For Nginx, add gzip on; to your server config block. Most hosting providers offer a one-click option in their control panel.
2. Compress text-based file types. Target HTML, CSS, JavaScript, JSON, XML, SVG, and plain text files. Do not compress images, videos, or PDFs — they are already compressed in their native formats and gzip will not help.
3. Consider Brotli compression too. Brotli is a newer compression algorithm that achieves even better ratios than gzip. Most modern browsers support it. If your server supports Brotli, enable it alongside gzip as a fallback.
4. Verify compression is working. Check your response headers in browser developer tools. Look for Content-Encoding: gzip (or br for Brotli) in the response headers. If it is missing, compression is not active.
5. Pre-compress static files if possible. For files that never change (like production JavaScript bundles), you can pre-compress them at build time and serve the compressed versions directly. This eliminates the server-side compression overhead entirely.

Common Mistakes

• Not enabling it at all. A surprising number of sites serve uncompressed text files. This is the lowest-hanging performance fruit available — check your server configuration and turn it on.
• Compressing already-compressed formats. Applying gzip to JPEG, PNG, MP4, or ZIP files wastes CPU cycles and can sometimes make files slightly larger. Only compress text-based formats.
• Setting the compression level too high. Maximum compression (level 9) uses significantly more CPU for marginal size improvements over moderate levels (5–6). The default level is usually the best balance of speed and compression.
• Forgetting to check after server changes. Server updates, migrations, or configuration changes can accidentally disable compression. After any server change, verify that Content-Encoding headers are still present.