A step-by-step guide on how to break down LCP and identify key areas to improve.
Published: April 30, 2020, Last updated: March 31, 2025
Largest Contentful Paint (LCP) is one of the three Core Web Vitals metrics, and it represents how quickly the main content of a web page is loaded. Specifically, LCP measures the time from when the user initiates loading the page until the largest image or text block is rendered within the viewport.
To provide a good user experience, sites should strive to have an LCP of 2.5 seconds or less for at least 75% of page visits.
A number of factors can affect how quickly the browser can load and render a web page, and delays across any of them can have a significant impact on LCP.
It's rare that a quick fix to a single part of a page will result in a meaningful improvement to LCP. To improve LCP, you have to look at the entire loading process and make sure every step along the way is optimized.
Understanding your LCP metric
Before optimizing LCP, developers should seek to understand if they even have an LCP issue, and the extent of any such issue.
LCP can be measured in a number of tools and not all of these measure LCP in the same way. To understand LCP of real users, we should look at what real users are experiencing, rather than what a lab-based tool like Lighthouse or local testing shows. These lab-based tools can give a wealth of information to explain and help you improve LCP, but be aware that lab tests alone may not be entirely representative of what your actual users experience.
LCP data based on real users can be surfaced from Real User Monitoring (RUM) tools installed on a site, or by using the Chrome User Experience Report (CrUX) which collect anonymous data from real Chrome users for millions of websites.
Using Chrome DevTools CrUX LCP data
The Performance panel of Chrome DevTools shows your local LCP experience next to the page or origin's CrUX LCP in the live metrics view, and in the Insights of a performance trace including a breakdown of the LCP subpart timings (that we will explain shortly).