BeforeThe Largest Contentful Paint metric measures how long it takes for the main visible content to appear. On most sites, that is a hero image or above-the-fold banner. If that image is a large JPEG served without WebP or AVIF encoding, without a preload hint, and without proper width and height attributes, LCP will be slow regardless of everything else on the page. This is the single most common LCP failure we find, and it is fixable without redesigning the page.
AfterGoogle's Page Experience system uses Core Web Vitals as ranking inputs. Sites with poor LCP, CLS, or INP field data are at a disadvantage in competitive search results, all other factors being equal. When Core Web Vitals pass in field data, that disadvantage is removed. For businesses in competitive UK verticals where multiple strong sites are competing for the same positions, this is a material ranking factor.
BeforeAnalytics tags, chat widgets, advertising pixels, and social sharing scripts load on most business websites. When these scripts are not loaded asynchronously or deferred correctly, they block the main thread and delay the page becoming interactive. Interaction to Next Paint, which measures responsiveness to user input, is directly affected by main thread congestion. Every additional third-party tag that loads synchronously costs measurable INP performance.
AfterWhen pages load faster and do not shift layout mid-load, mobile visitors stay longer. UK mobile users on 4G and 5G connections are sensitive to load time. The relationship between page load speed and bounce rate is well-documented in both Google's own research and in the analytics of sites we have worked on. A two-second improvement in LCP typically produces a measurable reduction in mobile bounce rate within a few weeks of implementation.
BeforeLayout shift happens when elements move on screen after the initial render. The most common causes are web fonts loading and swapping in after the page appears, images without declared dimensions, and above-the-fold advertisements loading in reserved but incorrectly sized containers. CLS is one of the most frustrating metrics for users because the page visually rearranges itself mid-read. It is also one of the most fixable with targeted interventions.
AfterSpeed affects conversion as well as engagement. A visitor who has waited four seconds for a product page to load is less likely to add to cart than one who saw it render in under two seconds. For landing pages and checkout flows, the performance gap between a passing Core Web Vitals page and a failing one can have a direct effect on revenue per session.
BeforeMany sites, particularly those built on React or other JavaScript-heavy frameworks, ship large JavaScript bundles to the browser. When the bundle is not code-split, every visitor downloads the entire application's JavaScript before the page becomes interactive. This inflates Total Blocking Time, delays INP, and creates poor mobile performance specifically because mobile CPUs process JavaScript more slowly than desktop CPUs. UK mobile users on variable 4G connections experience this most acutely.
AfterPerformance degrades over time as new content is added, third-party scripts accumulate, and plugins are updated. The monitoring setup we implement gives you ongoing field data visibility so degradation is caught early rather than discovered during the next audit. The fix is not a single event. The monitoring makes it a continuous baseline.