Does Page Speed Actually Matter?

Here's what real data says about how Core Web Vitals correlate with search traffic.

Based on analysis of 150,735 pages · Last 30 days

TTFB

Strong correlation
Measures server responsiveness. How long the server takes to respond.
Avg. value
0.51 s
Good threshold
< 0.8 s
Sample
23,655

CLS

Moderate correlation
Measures visual stability. How much the page layout shifts during loading.
Avg. value
0.08
Good threshold
< 0.1
Sample
26,626

SI

Moderate correlation
Measures how quickly page content is visually populated.
Avg. value
5.59 s
Good threshold
< 3.4 s
Sample
23,618

LCP

Weak correlation
Measures loading performance. How long until the largest element is visible.
Avg. value
7.97 s
Good threshold
< 2.5 s
Sample
26,555

FCP

Weak correlation
Measures perceived load speed. When the first content becomes visible.
Avg. value
2.74 s
Good threshold
< 1.8 s
Sample
23,655

FID

Insufficient correlation
Measures input latency. Delay before the browser processes the first user interaction.
Avg. value
0.38 ms
Good threshold
< 100 ms
Sample
26,626

Google's Core Web Vitals Thresholds

Metric Good Needs Improvement Poor
LCP
Largest Contentful Paint (LCP)
 < 2.5 s 2.5 s - 4.0 s > 4.0 s
CLS
Cumulative Layout Shift (CLS)
 < 0.1 0.1 - 0.25 > 0.25
INP
Interaction to Next Paint (INP)
 < 200 ms 200 ms - 500 ms > 500 ms
FCP
First Contentful Paint (FCP)
 < 1.8 s 1.8 s - 3.0 s > 3.0 s
TTFB
Time to First Byte (TTFB)
 < 0.8 s 0.8 s - 1.8 s > 1.8 s
FID
First Input Delay (FID)
 < 100 ms 100 ms - 300 ms > 300 ms
SI
Speed Index
 < 3.4 s 3.4 s - 5.8 s > 5.8 s

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