One of the easiest and most effective ways to make a web page load fast is to compress the data sent from the server to the browser. Gzip and Brotli are compression methods that, when enabled on the web server, greatly reduce file sizes. This guide explains how compression works and how to enable it.
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Why Does Compression Speed Things Up?
Web pages consist largely of text: HTML, CSS and JavaScript files. Text data is highly compressible — because it contains repeating patterns. The server sends the file compressed; the browser decompresses it. The result: data carried over the network drops by 70-80%, and the page loads noticeably faster.
This gain is especially felt on slow connections and mobile devices. Page speed also affects user experience and SEO through Core Web Vitals.
The Difference Between Gzip and Brotli
| Property | Gzip | Brotli |
|---|---|---|
| Release year | 1992 — a long-standing standard | 2015 — developed by Google |
| Compression ratio | Good | ~15-20% better than Gzip |
| Browser support | Universal | All modern browsers |
| Recommended use | Backward compatibility | Ideal for static content |
Serving both is the best approach: browsers that support Brotli get Brotli, those that do not get Gzip. The browser announces the method it supports with the Accept-Encoding header.
Enabling Compression on Nginx
On Nginx, Gzip is built in; it is turned on by adding a few lines to the configuration file:
gzip on;
gzip_comp_level 5;
gzip_min_length 256;
gzip_types text/plain text/css application/json
application/javascript text/xml application/xml
image/svg+xml;For Brotli, Nginx's ngx_brotli module needs to be installed; then it is enabled with the brotli on; and brotli_types lines.
Which Files Should Be Compressed?
- Compress: HTML, CSS, JavaScript, JSON, XML, SVG and plain text — these shrink significantly.
- Do not compress: Already-compressed files like JPEG, PNG, WebP, MP4, ZIP. Recompressing them does not reduce size, it only spends CPU.
- Very small files: For files smaller than a few hundred bytes the compression gain can be less than the overhead — that is why
gzip_min_lengthis set.
Verifying Compression
You can verify that compression works from the response headers. In the output of curl -I -H "Accept-Encoding: br,gzip" https://yoursite.com you should see a content-encoding: br or gzip line. The browser's developer tools (Network tab) also show this.
Frequently Asked Questions
Does compression slow down the server?
Compression uses a small amount of CPU, but because it greatly reduces the data carried over the network, the net effect is a clear speedup. Caching the compressed version of static files removes the CPU load too.
Should I prefer Gzip or Brotli?
Serve both. Brotli compresses better and all modern browsers support it; Gzip remains a safe fallback for old clients.
If I use a CDN, should I still enable compression?
Many CDNs do compression themselves; still, having it enabled on your origin server too ensures the CDN receives compressed content and keeps caching consistent.