Performance Tools
GZIP Compression Checker
Check whether a website serves compressed (GZIP/Brotli) content.
Enter a domain to check whether it serves compressed content.
JustChecker tracks your website's performance signals continuously.
Frequently Asked Questions
Text-based content (HTML, CSS, JavaScript) typically compresses to 60-80% smaller with GZIP, meaningfully reducing transfer time, especially for visitors on slower connections.
Most modern web servers support it, but it sometimes needs explicit configuration (a module or directive) that's occasionally overlooked, particularly on older server setups or custom-configured infrastructure.
Not meaningfully - image formats like JPEG and PNG are already compressed internally, so applying GZIP on top provides negligible additional benefit and is generally not applied to them by well-configured servers.
It requires a small amount of extra CPU time on the server to compress each response - for virtually all real-world traffic levels this is a worthwhile trade for the bandwidth and load-time savings, but very high-traffic sites sometimes tune compression levels to balance the two.
They check for different compression algorithms - GZIP is the older, universally-supported standard; Brotli is newer and generally achieves better compression ratios, but isn't supported by every legacy client.
Indirectly, through page speed - faster-loading pages tend to perform better on Core Web Vitals and page-experience signals, both of which factor into modern search ranking.