Compression Checker

A compression checker tests whether a server sends a page compressed with gzip or Brotli and compares the transferred size with the uncompressed size. Compression is one of the cheapest speed wins.

This tool fetches the address you enter once, from our server, and reports what a crawler would receive. The URL is not stored; only a short-lived rate-limit counter is kept. Results show the page at the moment of the check and can differ from what a logged-in browser or a bot with different headers sees.

How to read the result and act on it

The result should show a content-encoding of gzip or br and a transferred size clearly smaller than the uncompressed size. Text formats such as HTML often shrink by well over half, so a tiny difference or no encoding signals a problem. If compression is missing, enable it at the server or CDN: mod_deflate or mod_brotli on Apache, gzip or brotli directives on Nginx, or a toggle in your CDN or hosting panel. Prefer Brotli for text where supported and keep gzip as a fallback. After enabling, retest and confirm the vary: accept-encoding header is present so caches serve the right version.

Common mistakes to avoid

A typical mistake is enabling compression only for HTML while leaving CSS, JavaScript, JSON and SVG uncompressed. Compressing already compressed formats such as JPEG, PNG, WebP or video wastes CPU for almost no gain. Setting very high compression levels on dynamic pages can raise response time and cancel the benefit. Forgetting the Vary header can cause a cache to serve compressed content to a client that cannot read it. A CDN may compress differently from your origin, so test the public URL, not just the server. Finally, compression does not replace removing unused code and oversized assets, which still need separate work.

Is Brotli better than gzip?

Brotli usually compresses text slightly smaller, but gzip is widely supported and acceptable.

Which files should be compressed?

Text formats such as HTML, CSS, JavaScript, JSON and SVG. Images and video are already compressed.

How do I enable gzip compression on my site?

Turn it on in your server config, such as mod_deflate on Apache or the gzip directive on Nginx, or switch it on in your CDN or hosting panel. Then retest the public URL to confirm the content-encoding header appears and the transfer size drops.

How do I check if Brotli is working?

Request the page with an Accept-Encoding header that includes br and look for content-encoding: br in the response. Browsers use Brotli over HTTPS when the server supports it, so test the live HTTPS URL, not a local or HTTP address.

• Page Size Checker: Measure the HTML size of a page and count its linked resources.
• HTTP Header Checker: View the response headers of a URL: status, server, cache, content type and more.
• Server Response Time Checker: Measure time to first byte and total download time for a URL from our server.

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