Core Web Vitals are loading, responsiveness and visual stability measures: Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift. They describe aspects of real page experience. A useful review distinguishes field measurements from controlled tests and connects poor results to specific templates, resources or interactions.
Read the current measures correctly
Good thresholds are LCP at or below 2.5 seconds, INP at or below 200 milliseconds and CLS at or below 0.1, assessed at the 75th percentile of field visits. Mobile and desktop can differ. Google uses Core Web Vitals within its ranking systems, but good results do not guarantee top positions. A Lighthouse performance score is a lab diagnostic, not a substitute for passing the field metrics or a complete assessment of page usefulness.
Find the cause behind a poor group
Start with field data in PageSpeed Insights or Search Console where available. Confirm whether the information represents a particular URL or a broader origin and note the collection window. Then run controlled tests on representative templates and record the largest content element, long interactions and shifting elements. Prioritise issues affecting important journeys or many pages. Retest under comparable conditions after changes and allow time for field data to reflect new visits. Keep business outcomes separate from technical metric reporting.
Keep a release note beside each measurement change. A template update, third-party script or traffic shift can alter the results, so the date and affected pages are needed to interpret later field trends.
Choose the right optimisation
For example, an equipment hire website may load its hero image late, stall while filters run and shift when availability cards appear. These are different problems: prioritising the hero can help loading, simplifying main-thread work can help response and reserving space can improve stability. Compressing every file blindly may miss the main issue. A plan should identify the affected metric and expected mechanism. Small sites may lack enough public field data, in which case lab work and suitable first-party measurement still provide useful evidence.
Core Web Vitals diagnostics can guide the performance priorities within technical SEO.
Common questions
Is First Input Delay still a Core Web Vital?
No. Interaction to Next Paint replaced FID in the Core Web Vitals set. Current reporting should use LCP, INP and CLS.
Does a score of 100 guarantee rankings?
No. A lab score is not a ranking guarantee, and search systems also assess relevance and other information beyond these experience measures.
Terms in this guide
- Core Web Vitals — A set of user experience measures covering loading, responsiveness and visual stability. The current metrics are Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift.
- Largest Contentful Paint — A loading measure that reports when the largest visible content element is rendered. Large hero images, slow delivery and render-blocking resources can delay it.
- Interaction to Next Paint — A responsiveness measure based on the delay between user interactions and the next visual update. Long tasks and excessive JavaScript can make interactions feel slow.
- Cumulative Layout Shift — A measure of unexpected layout movement while a page is being used. Reserving dimensions for images and other content helps reduce disruptive shifts.
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