Why website speed matters on mobile data, and how to fix it

In many of the markets we work in, most people reach the internet through a phone, often on prepaid mobile data. The GSMA’s Mobile Economy Africa report tracks how quickly that is growing. A page that feels fine on office Wi-Fi can be painfully slow, and expensive, on a phone. Speed is not a technical detail: it decides whether people stay.

Measure before you change anything

Start with PageSpeed Insights. It shows how real visitors experience your site, using data from the Chrome UX Report, and runs a Lighthouse test with suggestions. For a deeper look, WebPageTest lets you test from different countries and on slower connections.

Google sums up the experience in three Core Web Vitals: how fast the main content appears, how quickly the page responds to a tap, and how stable the layout is while it loads. They also form part of Google’s page experience signals in search.

The fixes that matter most

• Shrink your images. Photos are usually the heaviest part of a page. Serve them in modern formats such as WebP or AVIF, at the size they are shown, and compress them with a tool like Squoosh.
• Load what is below the fold later. Lazy loading means images and videos further down only load when someone scrolls to them.
• Cut what you don’t need. Every chat widget, tracking script and font adds weight. Keep the ones that earn their place.
• Serve from close to your visitors. A content delivery network keeps copies of your site around the world, so a visitor in Lagos, Paris or Jakarta loads it from nearby.
• Keep plugins and themes in check. On WordPress especially, each extra plugin can slow every page.

What good looks like

The HTTP Archive Web Almanac shows that most websites still fall short on mobile, which is exactly why a fast site stands out. Aim for the main content to appear within about two and a half seconds on a mid-range phone, and test on one, not only on a laptop.

Make it a habit

Speed slips over time as new images, scripts and features are added. Check your key pages every month, and test every big change before it goes live.