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Do review widgets slow your site down? We measured 9 of them

Which Core Web Vital a third-party widget actually affects, and why it is usually not the thing making your page slow.

Cumulative Layout Shift is the one

A widget that appears after paint pushes content down, and that shift is measured. Reserving the container height solves most of it.

LCP rarely, INP sometimes

LCP only if the widget is the largest element above the fold. INP if the script blocks the main thread — a loading question, not a size one.

Measure before blaming

A page with an unoptimised hero image and four tracking scripts has poor vitals regardless. Run it with and without the widget; it takes two minutes.

Lab versus field

Synthetic scores are for diagnosis. Field data in Search Console is what counts.

Read the full version

The full write-up is in review widgets and page speed.

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