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Concepts and practices for measuring and optimizing page load, rendering latency, and interaction speed in web UIs.
Frontend performance encompasses practices and principles to reduce page load times, rendering latency, and interaction delays in web UIs. It emphasizes measurable metrics (real‑user and lab testing), optimization workflows, and resource‑efficient architecture across build and runtime. Key levers include metrics, caching, code splitting, image and network optimization to improve UX and lower costs.
Measures time to render the largest visible element; important for perceived load speed.
Assesses interaction latency across user interactions; successor to classic First Input Delay metrics.
Measures time until the first byte of a response; indicator for server and network latency.
Case: Reduced checkout latency using critical CSS, preconnect, and targeted code splitting.
Case: Adaptive image formats, low‑priority loading and CDN tuning increased engagement and reduced dropouts.
Case: Audit identified expensive render‑path scripts; tree‑shaking and lazy loading improved time‑to‑interactive.
Establish a baseline with RUM and lab audits.
Prioritize and implement quick wins (images, cache, preconnect).
Automate continuously: integrate performance checks into CI and re‑measure.