How to measure LCP and what threshold to consider good

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LCP can be measured, like all Core Web Vitals, in the field, using the following tools:Chrome User Experience ReportPage Speed ​​InsightsSearch Console (Core Web Vitals report)You can also measure LCP with lab tools like Chrome DevTools , Faro , and WebPageTest . To make it easier for developers to understand the results, Google also provides limit thresholds dividing the cases into 3: Good , Requires Improvement , Poor . Google considers LCP below 2.5 seconds to be Good , while LCP above 4 seconds is considered Poor .Lcp Core Web Vitals Range EvaluationImage source LCP Scores: How to Improve ThemBefore talking about the actions to be taken to improve the LCP, it is good to understand what factors can influence low scores for this metric. Specifically, Google tells us:Slow server response timesRender-blocking JavaScript e CSSResource loading times.



Client-side renderingOnce your reference case has been Special Data identified, you will be able to proceed with the related resolution actions (which are in any case best practices that should always be implemented):Applying instant loading with the PRPL modelCritical rendering path optimizationCSS optimizationImage optimizationWeb font optimizationJavaScript optimizationFor more information on this, we suggest you read Google's official LCP optimization article .For more in-depth technical considerations regarding the LCP we recommend you read the official article on web.dev .First Input Delay (FID) and interactivityThe First Input Delay metric measures the time between the user's first interaction on a page and the time the browser responds .The FID is extremely important because it comes into play in the initial moments of the user's navigation, where the "first impression", quoting Google itself, is fundamental . Here Google refers to the first impression at the level of interactivity , specifying the difference compared to first impressions deriving from aesthetics and design.Speed ​​of reactivity is a much more measurable metric than aesthetic satisfaction and constitutes a very important marker of the quality of the user experience, which reasonably expects immediate responses from the websites to which it makes a request . By request we refer for example to actions such as:clicking on linkstap su pulsanticlick on JavaScript-based controlsand not to actions such as scrolling or zooming.





But why can delays in response occur after the first interaction? Usually because the browser is busy doing something else at the time , such as parsing and executing a large JavaScript file.Be careful, what the FID measures is only the "delay" in processing the events and not the time for complete processing of the event itself or the time taken by the browser to update the interface once the interaction has taken place. In fact, Google specifies that if the latter were included in the FID metric, developers would be incentivized to respond asynchronously, which would cause a worsening of the user experience.