What Core Web Vitals measure
Core Web Vitals are a small set of metrics that capture real user experience: how fast the main content loads, how quickly the page responds to interaction, and how stable the layout is while loading.
- Largest Contentful Paint: how fast the main content appears.
- Interaction to Next Paint: how quickly the page responds to input.
- Cumulative Layout Shift: how much the layout moves unexpectedly.
What slows most sites down
The most common performance problems are large images, heavy JavaScript, render-blocking resources, and layouts that shift as content loads.
These are usually fixable without rebuilding the whole site, once you know where the weight is.
What to fix first
Performance work has diminishing returns, so priority matters. Start with the changes that affect the most users on the most important pages.
- Optimize and correctly size images, and serve modern formats.
- Reduce and defer non-critical JavaScript.
- Reserve space for images and embeds to stop layout shift.
- Serve static content from a CDN and cache aggressively where safe.
Measure with real data
Lab tools are useful, but real user data shows how the site performs on actual devices and networks. Optimizing for real conditions avoids chasing scores that do not reflect experience.
Performance is ongoing: new features add weight, so it is worth monitoring rather than fixing once and forgetting.
What are Core Web Vitals?
They are Google's metrics for real user experience: loading (Largest Contentful Paint), interactivity (Interaction to Next Paint), and visual stability (Cumulative Layout Shift).
What usually slows a website down?
Large images, heavy JavaScript, render-blocking resources, and layouts that shift while loading are the most common causes, and most are fixable without a rebuild.
Does performance affect SEO?
Yes. Core Web Vitals are a ranking signal, and faster pages also improve engagement and conversion, so performance benefits both search and business outcomes.