Brotli vs Gzip: Compression That Cuts Load Time

When a browser requests your page, the server does not have to send text files (HTML, CSS, JavaScript) at full size. It can compress them first, send a smaller package, and the browser unpacks it before rendering. Fewer bytes over the network means faster loading, especially on mobile connections. The two most common methods are Gzip and Brotli.

Gzip: the proven classic

Gzip has been around for decades and every browser and server supports it. It typically shrinks text files by 60-75%. A 100 KB CSS file easily drops to 25-30 KB. It is reliable and fast to compress, so it was the default choice for a long time.

Brotli: newer and more efficient

Google built Brotli specifically for the web. At its highest compression levels it produces files 15-25% smaller than Gzip for the same content. For CSS and JavaScript that is a noticeable saving. The trick is that Brotli ships with a built-in dictionary of common web patterns, so it packs exactly what sites tend to send more tightly. Every modern browser supports it over HTTPS.

What it means in practice

Imagine a page whose text resources total 400 KB uncompressed. Gzip brings them down to about 110 KB, and Brotli to about 90 KB. Those 20 KB of difference on a slow 4G link mean a few dozen milliseconds less — and, more importantly, less data the user pays for. On a high-traffic site the bandwidth savings add up.

Static vs. dynamic content

An important nuance: Brotli at its highest level (11) is slow to compress, so it is used for static files that are compressed once and cached. For dynamic HTML generated on the fly, a lower Brotli level or Gzip is used, because there the compression speed must be instant. A good host configures this automatically.

How to check it works

Open developer tools in your browser (F12), the Network tab, click a CSS or JS file, and look at the response header content-encoding. If it says br, Brotli is running; if it says gzip, Gzip is running. If there is nothing, compression is off and you are losing speed for no reason.

With us Brotli and Gzip are enabled by default, alongside free SSL and a global CDN, so every visitor gets the smallest possible package. See the plans or the details of SEO hosting.