Try it yourself
Core Web Vitals for one page, measured from real visitors. Three of these are inside Google's "good" band.
Which one is failing?
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How long until the biggest thing on screen appears. Good is 2.5 seconds or less, so 2.1 passes — though it is close enough that a heavier hero image would push it over.
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How long the page takes to respond when somebody taps something. Good is 200 ms or less, so this passes. INP replaced FID as a Core Web Vital in 2024.
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This is the one. CLS measures how much the page jumps around while loading. Good is 0.10 or less and anything above 0.25 is rated poor, so 0.34 is well into failing. It is the metric visitors feel most directly — it is why you tap the wrong button as an advert loads above it. Usually caused by images and embeds with no width and height set.
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How long the server took to start answering. Not a Core Web Vital itself, but it sets the ceiling for everything else. Under 0.8 s is good.
Pick a line. Every one of them has an answer.
Show me the answer
CLS 0.34 Cumulative Layout Shift
This is the one. CLS measures how much the page jumps around while loading. Good is 0.10 or less and anything above 0.25 is rated poor, so 0.34 is well into failing. It is the metric visitors feel most directly — it is why you tap the wrong button as an advert loads above it. Usually caused by images and embeds with no width and height set.
The written version
Mobile page speed and Core Web Vitals →
How to check your own site for this, what to change, and how to confirm it worked.
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