If you can't measure it, you can't improve it. Here are the metrics that matter in 2025.
1. Interaction to Next Paint (INP)
INP has replaced FID as a Core Web Vital. It measures the responsiveness of your page to user interactions.
2. Largest Contentful Paint (LCP)
Still the gold standard for perceived load speed. Aim for under 2.5 seconds.
3. Cumulative Layout Shift (CLS)
Visual stability is crucial. Ensure your elements don't jump around as the page loads.