Performance Tools

Brotli Compression Checker

Check whether a website serves Brotli-compressed content.

Enter a domain to check whether it serves Brotli-compressed content.

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What Is Brotli?

Brotli is a newer compression format that usually makes text files 15-25% smaller than GZIP. Browsers request it with Accept-Encoding: br over HTTPS. This tool checks whether a server responds with Brotli.

When to Use It

When optimising page speed and Core Web Vitals.
After enabling Brotli on your server or CDN.

How to Use It

Enter the domain.
Check whether the response is Brotli-encoded.

Understanding the Result

Content-Encoding: br means Brotli is active. Many CDNs, including Cloudflare, enable it with one setting; on Nginx it needs the Brotli module.

Limitations

GZIP is still a perfectly good fallback - a site without Brotli but with GZIP is only slightly slower. Check GZIP with the GZIP Checker.

How to Enable Brotli

Cloudflare: Brotli is applied automatically for visitors whose browsers support it.
Nginx: install the ngx_brotli module, then add brotli on; and brotli_types text/css application/javascript application/json image/svg+xml;
Apache 2.4: enable mod_brotli and add AddOutputFilterByType BROTLI_COMPRESS text/html text/css application/javascript.
Static sites: many hosts (Netlify, Vercel) serve Brotli automatically.

Example Result

A 120 KB HTML page might transfer as about 25 KB with gzip and about 21 KB with Brotli. On a slow mobile connection that difference is noticeable, and it applies to every CSS and JavaScript file too.

Good to Know

Browsers only use Brotli over HTTPS.
Do not Brotli-compress images, videos or fonts that are already compressed (JPEG, WebP, MP4, WOFF2) - it wastes CPU for no gain.
Pre-compressing static files at build time lets you use the highest compression level without slowing responses.

Compare with the GZIP Checker and read our guide to compression and caching.

Frequently Asked Questions

Brotli generally achieves noticeably better compression ratios than GZIP for the same content, meaning smaller transferred file sizes and faster loads - most modern browsers support it, making it a strict upgrade where available.

No - the best practice is offering both, letting the server automatically serve Brotli to clients that support it and gracefully fall back to GZIP for those that don't, rather than choosing one exclusively.

Brotli support requires a specific server module or CDN feature that isn't always enabled by default, unlike GZIP which has been a near-universal standard for much longer - it sometimes needs to be explicitly turned on.

Every current major browser does, but this is why servers should still offer a GZIP fallback for any older or unusual client that doesn't negotiate Brotli support.

At higher compression levels, yes, Brotli can require more CPU time - many setups use it primarily for static, pre-compressed assets (where the compression cost is paid once, not per-request) rather than dynamically compressing every response live.

Yes - many CDNs can compress content with Brotli at the edge regardless of what the origin server sends, which is a common, low-effort way to gain Brotli support without modifying origin server configuration.