Speed is often treated as something developers fix at the end. By then the decisions that make a site slow have already been made: a full-screen video in the hero, four font families, a carousel of uncompressed photographs. The cheapest place to make a site fast is in the design.
Measure what people feel
Google’s Core Web Vitals are a practical way to turn speed into numbers. Largest Contentful Paint measures how quickly the main content appears; it should be under 2.5 seconds. Interaction to Next Paint measures how quickly the page responds to a tap or click; under 200 milliseconds is good. Cumulative Layout Shift measures how much the page jumps around as it loads; it should stay under 0.1.
These are not abstract. The first is the wait. The second is the lag. The third is tapping the wrong button because an image loaded above it.
Test on a slow phone, not a fast laptop
A site tested on an office connection and a new laptop will always feel fast. Chrome’s developer tools can throttle the network and processor to resemble a mid-range phone on mobile data, which is closer to how much of the audience actually arrives.
Field data matters even more. Once a site has real traffic, the numbers from real visitors show what lab tests can only estimate.
Every image is a decision
Images are usually the heaviest part of a page. Serving them in modern formats such as WebP or AVIF, at the size they are actually displayed, and loading the ones below the fold only when needed often halves page weight without changing a single pixel the visitor sees.
Setting the width and height of each image also stops the layout from jumping while it loads, which fixes most layout shift problems at once.
Fonts and scripts are the quiet cost
Every font weight is a file. Every third-party script, a chat widget, a heatmap tool, a second analytics tag, adds work the browser must do before the page responds. None of these is heavy on its own. Together they are often the reason a well-built site feels sluggish.
We ask for each one what it earns. Many turn out to have been added once for a campaign and never removed.
Motion should not cost the first impression
Animation can make a site feel considered, but it should never hold the content hostage. Text should be readable before the entrance effect finishes, and a hero video should have a lightweight poster image that appears immediately.
Keep testing after launch
Sites get slower over time as content, plugins and tracking accumulate. A performance budget, a limit on page weight or load time checked on each release, keeps the launch-day speed from quietly wearing away.
