Web development and performance
What is Brotli?
Brotli is a compression algorithm that typically produces 15 to 20 percent smaller text responses than gzip at equivalent CPU cost. Every current browser supports it, and enabling it is one of the cheapest bandwidth savings available.
Also called: br compression
Where the saving lands
On HTML, CSS, JavaScript, SVG, JSON and XML — everything textual. Images and fonts are already compressed and gain nothing, so a configuration that tries to compress them wastes CPU for no benefit.
How to check
Request your page with an Accept-Encoding header offering br and read the Content-Encoding in the response. If it says gzip, Brotli is not enabled — which is common on shared hosting and almost universal on modern CDNs.
The realistic impact
On a 150 KB HTML document the difference is roughly 20 to 30 KB per request. Not transformative alone, and it compounds with everything else on a slow connection — and it costs one configuration line.
Where this is covered in depth
A definition can only go so far. Core Web Vitals, and the order that actually reduces them covers this properly — 3 minutes, free, no email required.
Who wrote this
Anas Bin Masud builds e-commerce sites and does technical SEO for businesses in the UK, Canada and Pakistan. These definitions come from client work rather than from a content brief — where an entry describes a mistake, it is usually one found on a real site. More about how I work.