How do you detect LCP?

To detect the Largest Contentful Paint (LCP) of a web page, you can use a variety of tools and techniques. Here are a few options:

Chrome DevTools: This is a set of developer tools that is built into the Google Chrome browser. It includes a Performance panel that allows you to record and analyze the performance of your website. You can use this panel to get a detailed breakdown of your website’s performance, including the LCP. To do this, follow these steps:

  1. Open the website in Google Chrome.
  2. Press F12 to open the Chrome DevTools.
  3. Click on the “Performance” tab.
  4. Click the “Record” button to begin recording the performance of the page.
  5. Wait for the page to load.
  6. When the page is finished loading, click the “Stop” button to stop recording.

Once the recording is complete, the Performance panel will show a summary of the page’s performance, including the LCP. The LCP is displayed as a timestamp, with a lower value indicating better performance.
Lighthouse: This is an open-source tool developed by Google that allows you to analyze the performance, accessibility, and SEO of your website. It includes a section on Core Web Vitals where you can see the performance of your website on the 3 Core Web Vitals, including the LCP. To use Lighthouse to detect the LCP of a web page, follow these steps:

  1. Open the Lighthouse tool in Chrome by going to the URL “chrome://lighthouse”.
  2. Enter the URL of the website that you want to test in the “URL” field.
  3. Click the “Generate report” button.
  4. Wait for the report to generate.
  5. When the report is complete, click on the “Opportunities” tab.
  6. Scroll down to the “Diagnostics” section and look for the “Largest Contentful Paint” row. The LCP score will be displayed in the “Value” column.


Third-party monitoring tools: There are also many third-party tools and services that allow you to monitor the LCP of your website over time and get alerts when the LCP exceeds a certain threshold. These tools often provide detailed performance data and can be useful for identifying and fixing performance issues.

In addition to these tools, you can also manually test the LCP of a web page by simply loading the page in a web browser and timing how long it takes for the main content of the page to become visible. This can be a useful way to get a feel for the overall performance of a page, but it may not provide as much detail as the tools listed above.

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