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Google’s June 2021 Lighthouse Update Changes PageSpeed Insights Performance

Google updated how their PageSpeed Insights scores are calculated by releasing a new version of Lighthouse on June 1, 2021. Lighthouse is a tool built into Google Chrome that lets you know how well your site is performing against Google's standards for a better open web. At RebelMouse, our team keeps up with updates from Google closely, and reads all of their release notes and GitHub updates.

This latest upgrade to Lighthouse had a negative impact on one of our previous methods for loading JavaScript in the JavaScript element of our Layout & Design Tool. Performance scores dropped as much as 20–60 points for sites that were using the JavaScript element in its previous state. However, our team kept on top of Google's changes, and developed a new approach that we call the post Largest Contentful Paint (LCP) method. LCP is a metric in Google's Core Web Vitals that measures the time it takes to load the main content on a page. Our post-LCP method loads JavaScript immediately after the LCP event has completed. Thanks to this new approach, scores in our site network have largely stayed intact, and many of them significantly outperform the open web.

Additionally, on June 17, 2021, we released a platform update to improve our Load Blocking element, which fires JavaScript immediately after the page has completed loading. Previously, this method received negative performance scores after Google's June 1 changes. But now that we've made our update, no changes are necessary to sites that are using this element.

It's important to note that Chrome User Experience Report (CRUX) scores and Lighthouse scores are not entirely aligned and often disagree with each other. Please follow best practices on our platform, as described here, to stay ahead of Google's algorithm changes.

If you have any questions about the latest version of Lighthouse, or any of these updates, please email support@rebelmouse.com or talk to your account manager today.

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