Performance

Performance is what makes a PWA feel app-like rather than web-like. Core Web Vitals quantify the experience — load, responsiveness, and visual stability — while platform primitives like View Transitions and Speculation Rules let a PWA animate between views and pre-render likely next pages. Service-worker caching turns repeat visits into instant loads.

These entries cover the metrics, their thresholds, and the levers that move them.

In this section

Core Web VitalsLCP, INP, and CLS — what each measures, the good thresholds at the 75th percentile, and the PWA-specific levers.

View TransitionsAnimating between DOM states with document.startViewTransition() and the view-transition pseudo-element tree.

The app shell modelPre-caching the minimal HTML, CSS, and JavaScript needed to paint the UI, then hydrating with dynamic content.

Planned topics

Reserved in the coverage matrix and filled in over time:

• Speculation Rules

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