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Do excessive third-party-scripts increase cls and lower core-web-vitals?

Asked on Sep 24, 2025

Answer

Excessive third-party scripts can negatively impact Core Web Vitals, particularly by increasing Cumulative Layout Shift (CLS) due to delayed rendering and layout changes. These scripts can also affect other metrics like Largest Contentful Paint (LCP) and First Input Delay (FID) by blocking rendering and delaying interactivity.

Example Concept: Third-party scripts can cause layout shifts by loading asynchronously and injecting content or styles after the initial render. This can lead to unexpected changes in layout, contributing to a higher CLS score. To mitigate this, consider deferring non-critical scripts, using async or defer attributes, and ensuring that any dynamically injected content reserves space in advance.

Additional Comment:

Evaluate the necessity of each third-party script and remove any that are not essential.
Use the "async" or "defer" attributes to load scripts without blocking the initial render.
Reserve space for dynamic content to prevent layout shifts.
Regularly audit your website's third-party scripts using tools like Lighthouse or WebPageTest.

✅ Answered with Core Web Vitals best practices.

Ask any question about Performance here... and get an instant response.

Do excessive third-party-scripts increase cls and lower core-web-vitals?

Asked on Sep 24, 2025

Answer

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