GZIP Compression Test
See whether a website serves its pages compressed with GZIP or Brotli, the original HTML size, the compressed size and how much data and loading time compression saves.
How to useDoes the site use GZIP?
Available in: 
GZIP Compression Test: what it is for
Enter a page address and see whether the server delivers the HTML compressed with GZIP, Brotli or Zstandard, the original HTML size, the GZIP size and the savings as a percentage. The chart compares both sizes and the table estimates download time on 3G, 4G and fiber, with and without compression.
If compression is off, the tool tells you how to turn it on.
How to use
- Enter the page address.
- Tap Test compression.
- See the savings and the download time.
When to use it
- Check whether GZIP is on after editing .htaccess.
- Find a cause of a slow site.
- Compare compression across hosts.
Frequently asked questions
What is GZIP compression?
A way to pack HTML, CSS and JavaScript before sending them to the browser, which unpacks them instantly. Text compresses very well: a 100 KB page usually arrives as 20 to 30 KB, which makes the site faster.
GZIP or Brotli, which is better?
Brotli is newer and compresses on average 15% to 20% more than GZIP, and every current browser supports it. If your server has Brotli, use it; GZIP stays as a fallback.
How do I enable GZIP on my site?
On Apache, enable mod_deflate in .htaccess; on Nginx, use gzip on; with the text/html, text/css and application/javascript types. Hosts and CDNs like Cloudflare usually do this automatically.
Do images need GZIP too?
No. JPG, PNG, WebP, videos and WOFF2 fonts are already compressed. Running GZIP on them barely shrinks them and wastes CPU. Compression is for text: HTML, CSS, JS, JSON, SVG and XML.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 are free.