GZIP & Brotli Compression Test Tool Online
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Check whether your site uses GZIP or Brotli compression. See transfer savings, compression status, and practical GEO performance fixes for faster crawling and better user experience.
Enter a URL to test compression:
How the Compression Test Works
The API fetches your page with browser-like compression support and reads the response headers.
- Safe URL check, the host is validated before the server requests it.
- Compression request, the fetch includes gzip, deflate, and br in Accept-Encoding.
- Header analysis, the content-encoding and content-length headers are read from the response.
- Savings estimate, the decoded body size is compared with compressed transfer size when available.
Why Compression Matters
Text compression is one of the simplest speed wins for HTML, CSS, and JavaScript.
- Faster first load, smaller files reach visitors sooner on mobile networks.
- Better crawl efficiency, search engines and AI crawlers can retrieve pages with less bandwidth.
- Lower hosting cost, compressed responses reduce data transfer from your server or CDN.
- Better Core Web Vitals support, smaller render-blocking CSS and JavaScript can improve LCP and INP.
Compression Encoding Comparison
| Encoding | Best for | Notes |
|---|---|---|
| br | HTML, CSS, JS | Usually the best compression for modern browsers. |
| gzip | HTML, CSS, JS | Universal fallback with strong savings. |
| none | Already compressed assets | Bad for text files unless the response is tiny. |
For a wider performance audit, use our website speed optimization guide.
Next steps
GZIP / Brotli Test related tools and articles
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GZIP and Brotli Compression: FAQ
What does the GZIP and Brotli Compression Test check?
It requests a URL with Accept-Encoding support for gzip, deflate, and br, then reports the server content-encoding header, compressed transfer size when available, decoded size, and estimated savings.
Is Brotli better than GZIP?
Brotli often compresses text files smaller than GZIP, especially HTML, CSS, and JavaScript. GZIP is still widely supported and much better than no compression.
What files should be compressed?
Compress text-based assets such as HTML, CSS, JavaScript, JSON, XML, SVG, and fonts. Do not rely on GZIP for already-compressed images such as JPEG, PNG, WebP, or AVIF.
What is a good compression savings percentage?
Savings of 60 to 80 percent are common for HTML, CSS, and JavaScript. Lower savings can be normal for very small pages or content that is already minified.
Why is content-length sometimes missing?
Some servers use streaming, chunked transfer, dynamic compression, or CDN transformations that do not expose compressed content-length in the response headers.
Does compression help SEO?
Compression improves load time and bandwidth efficiency. Faster pages can support stronger Core Web Vitals, better crawl efficiency, and better user experience.
How do I enable Brotli or GZIP?
Use your CDN, hosting panel, Nginx, Apache, or framework adapter settings. Cloudflare, Vercel, Netlify, and most modern CDNs can compress text responses automatically.
Is this compression test free?
Yes. It is a free online compression checker with no signup.
Need a Faster, Lighter Website?
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