Speed is the first impression. Users form a judgment within a few hundred milliseconds: either the interface is responsive and trustworthy, or it’s laggy and suspect. Designing for speed starts before the first pixel — in information architecture, asset strategy, and interaction plans that respect device constraints.
Reduce the cost of first paint. Ship clean HTML, critical CSS inlined for above-the-fold content, and defer all non-essential JavaScript. Replace heavy hero videos with high-quality poster images and a play control. Use modern image formats (AVIF/WebP) and set width/height to avoid layout shift. Preload the most important font and consider a system font stack to cut 3rd-party latency.
Count requests like calories. Bundle thoughtfully, but avoid giant monoliths. Prefer native features (details/summary, CSS animations, form validation) over JavaScript equivalents. Audit third-party scripts; each one adds CPU, network, and privacy risk. If a script doesn’t pay for its weight, remove it.
Design interactions for immediacy. Targets should be large enough, labels clear, and feedback instant. Use optimistic UI only when safe and reversible. Keep transitions short (150–250ms) and GPU-friendly. For scroll performance, prefer CSS transforms and will-change sparingly. Establish performance budgets: e.g., LCP under 2.5s, INP under 200ms, CLS under 0.1.
Measure continuously. Add RUM (real user monitoring) for Core Web Vitals, split by device class and connection type. Turn insights into backlog items: compress images, reduce blocking scripts, remove dead CSS, and cache aggressively at the edge. Celebrate wins by correlating speed gains with conversion and retention lifts.
Performance is a product decision. When you design for speed, you design for inclusion — for low-end devices, constrained networks, and people who need clarity fast. Fast isn’t a nice-to-have; it’s how great web design feels.