Performance

GZIP Compression Test

Enter any URL and we'll request it with Accept-Encoding: gzip, br, deflate and tell you which compression (if any) the server sent back.

What is a GZIP compression test?

A GZIP compression testrequests a URL with compression enabled and reports what the server returns — gzip, brotli, deflate or none — plus the size saved. It's the fastest way to check gzip compression on any site, free and online.

Check GZIP compression on any website

Paste a URL to check gzip website responses (a gzip test url). We show the Content-Encoding the server sends and the compressed vs uncompressed size — check gzip compression online in seconds.

GZIP vs Brotli

Brotli usually compresses text slightly smaller than gzip and is widely supported — enable it where possible with gzip as the fallback. This tool detects whichever the server uses.

Why compression matters

Compressing HTML, CSS and JS can cut transfer size by 60–80%, speeding up load time and improving Core Web Vitals. If a URL isn't compressed, enabling gzip/brotli is an easy win.

More performance tools

Pair this with our Page Speed Test, HTTP Headers Checker, CDN Checker and the full free SEO tools suite.

Frequently asked questions

A GZIP compression test requests a URL with Accept-Encoding: gzip, br and reports which compression the server returns (gzip, brotli, deflate, or none) along with the size saved. It's the quickest way to check gzip compression on any website.
Paste the URL into the gzip test above and run it. We send a compression-aware request and show the Content-Encoding the server responds with, plus the compressed vs uncompressed size so you can see the savings.
Brotli (br) usually compresses text a bit smaller than gzip and is supported by all modern browsers, so enable it where you can and keep gzip as the fallback. This tool detects either one.
Compressing text assets (HTML, CSS, JS) can cut their transfer size by 60–80%, which speeds up load time and improves Core Web Vitals. If a URL isn't compressed, enabling gzip/brotli is one of the easiest wins.
Completely free and online, with no account required. It's part of WebsiteAuditTools' free suite of performance tools.