When a site takes six seconds to become interactive on mobile, every other marketing investment is taxed. Paid traffic lands and bounces. Organic rankings slide on the page-experience signal. Conversion rate sags and everyone blames the offer.
The business case for performance work is straightforward arithmetic. If a page converts at two per cent and you improve load time enough to lift that to 2.7 per cent, you have increased revenue by more than a third without increasing spend. Very few campaigns deliver that return.
In practice the biggest wins are unglamorous. Shipping properly sized modern image formats, removing render-blocking third-party scripts, and eliminating layout shift from late-loading fonts typically account for the majority of the improvement.
Fonts deserve specific attention. Loading a display face without proper preloading causes the text to reflow after paint, which is both a visible jolt and a measurable layout-shift penalty. Self-hosting and preloading the font files solves it outright.
The measurement discipline matters as much as the fixes. Field data from real users, not lab scores, is what search engines and your finance team actually experience. Track it continuously, because performance regresses quietly with every new tag and feature.