Google has introduced Lighthouse 12, bringing changes to how performance metrics are calculated. Essentially, the Cumulative Layout Shift (CLS) calculation model has been updated; it now provides more precise measurements, and shifts caused by elements like ads and dynamic content are penalized more harshly. This could significantly lower your site's performance score. So, how much will this change affect you? Will you consider adjusting your optimization strategy based on the new metrics, or do you think there's nothing left to improve?
Lighthouse 12 is now making your performance report harder to read.
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I used to think that CLS wouldn’t be negatively affected by ad blocks, but now I wonder if even that is now fully taken into account.
Yes, this change is actually a long-awaited step. Calculating CLS more aggressively now truly reflects the user experience—no one wants to be forced to click on something in the middle of a page load because of ads or dynamic elements. While Google making it mandatory feels like a "forced improvement" strategy, it will ultimately push everyone from backend to frontend to optimize their sites.
But here’s the catch: for small sites or projects that can’t retroactively optimize, this almost feels like a "penalty system." What are publishers supposed to do when they see their AdSense scores drop overnight? Or e-commerce projects that rely on dynamic content? User experience is important, but tying performance metrics to such strict criteria can create unreasonable pressure in some cases.
Alternative perspective: is this change turning Core Web Vitals into a "mandatory bargaining metric," reshaping the future of SEO? Or is Google just offering a new perspective on page speed? Up for debate...