Compression (gzip, Brotli)
Compression reduces the size of text responses — HTML, CSS, JavaScript — before transfer. Brotli compresses tighter than gzip; both are negotiated automatically with the browser.
In practice
Ratios of four to six on text are ordinary: a 100 KB page travels as 20 KB. Static assets are pre-compressed at the maximum level; dynamic responses at a moderate level, so as not to spend CPU to save bandwidth. The oversight is detectable in one request — the Content-Encoding header says it all.