ZenovayTools

HTTP Compression Checker

Check if your web server supports gzip and Brotli compression. Compares compressed vs uncompressed response sizes, calculates compression ratio, checks Content-Encoding headers, and verifies Vary headers for correct CDN caching.

How to Use HTTP Compression Checker

  1. 1Enter a URL to test HTTP compression.
  2. 2The tool fetches the URL with gzip and Brotli Accept-Encoding headers.
  3. 3Compressed and uncompressed response sizes are compared.
  4. 4Compression ratio, Content-Encoding, and Vary headers are shown.
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Frequently Asked Questions

Why does HTTP compression matter for performance?▾
HTTP compression reduces the size of text-based resources (HTML, CSS, JavaScript, JSON, XML) sent over the network. Gzip typically reduces file sizes by 60-80%, and Brotli achieves 15-25% better compression than gzip. For large pages, this can save hundreds of kilobytes, significantly reducing time-to-first-byte (TTFB) and improving Core Web Vitals (LCP, FCP). Compression is especially impactful on slow mobile connections.
What is the difference between gzip and Brotli?▾
Gzip (Content-Encoding: gzip) is the older, universal compression standard supported by all browsers since 2010. Brotli (Content-Encoding: br) is Google's newer algorithm that achieves better compression ratios, especially for text content. Brotli is supported by all modern browsers (Chrome 49+, Firefox 44+, Safari 11+, Edge 15+). CDNs like Cloudflare and Fastly support both. If your server supports Brotli, it should be preferred — especially for static assets.
What is the Vary: Accept-Encoding header for?▾
When a server serves different compressed responses based on what the client supports, it must include Vary: Accept-Encoding in the response. This tells CDN proxies and caches that the response varies by the Accept-Encoding request header, so they cache separate versions for gzip vs. brotli vs. uncompressed. Without Vary: Accept-Encoding, a CDN might cache a gzip response and serve it to a client that cannot decompress gzip, causing garbled content.
Should I compress all content types?▾
Compress text-based content: HTML, CSS, JavaScript, JSON, XML, SVG, plain text, and web fonts (WOFF/WOFF2). Do NOT compress already-compressed formats: JPEG, PNG, WebP, AVIF, MP4, ZIP, PDF, WOFF2. Compressing pre-compressed binary content wastes CPU and may slightly increase size. Most web servers handle this automatically with a MIME type allowlist.
How do I enable Brotli on my server?▾
Nginx: install ngx_brotli module and add brotli on; brotli_comp_level 6; brotli_types text/html text/css application/javascript; to your config. Apache: install mod_brotli and use AddOutputFilterByType BROTLI_COMPRESS. Cloudflare: automatically applies Brotli to all responses. Node.js/Express: use the shrink-ray-current middleware. Caddy: enabled by default.