What is File Compression?
File compression reduces file sizes to improve page load times, which directly impacts Core Web Vitals scores and search rankings. Properly compressed images, JavaScript, CSS, and HTML files decrease server response times and bandwidth usage, improving both user experience and crawl efficiency for search engines.
Ecommerce SEO Glossary > Technical SEO > File Compression
What You Need to Know about File Compression
Impact on Core Web Vitals
This technique directly improves Largest Contentful Paint (LCP) and page load speeds, both critical ranking factors. Sites with properly compressed files typically load 40-60% faster than uncompressed versions.
Image Compression Is Critical
Images account for most page weight on typical websites. Using modern formats like WebP and AVIF, along with proper compression levels, reduces file sizes by 25-50% without visible quality loss.
Text File Compression Methods
Gzip and Brotli compression reduce HTML, CSS, and JavaScript file sizes by 70-90%. Brotli offers slightly better compression ratios and is supported by all modern browsers, making it the preferred choice.
Server Configuration Requirements
Compression must be enabled at the server level to work effectively. Most modern hosting platforms support automatic compression, but misconfigured servers often deliver uncompressed files, negating performance benefits.
Avoid Over-Compression
Excessive compression degrades image quality and can increase processing time. Finding the balance between file size and quality is essential—typically 80-85% quality for JPEG images maintains visual fidelity while achieving significant size reductions.
Mobile Performance Priority
Compressed files are especially important for mobile users on slower connections. Google’s mobile-first indexing means mobile page speed directly affects rankings, making compression a competitive advantage for sites targeting mobile traffic.
Frequently Asked Questions about File Compression
1. How do I enable file compression on my website?
Most hosting providers offer one-click compression in their control panels. For custom setups, enable Gzip or Brotli in your server configuration files (Apache’s .htaccess or Nginx config files).
2. Which file types should I compress?
Compress all text-based files (HTML, CSS, JavaScript, XML, JSON) and images. Don’t compress already-compressed formats like video files, PDFs, or ZIP archives—recompressing these files provides minimal benefit.
3. Does file compression actually improve search rankings?
Yes. Page speed is a confirmed ranking factor, and compression directly improves load times. Sites that load faster than competitors often rank higher, especially for competitive commercial keywords where user experience matters.
4. What’s the difference between Gzip and Brotli compression?
Brotli provides 15-20% better compression than Gzip and is now widely supported by browsers and CDNs. Use Brotli as your primary method with Gzip as a fallback for older browsers.
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