Core Web Vitals: which metric is hardest to pass?

14 Dec 2021

In June 2021, Google started using Core Web Vitals as a search result ranking factor. The Core Web Vitals are a set of three user experience metrics: Largest Contentful Paint, Cumulative Layout Shift, and First Input Delay.

For each of these metrics, Google defined thresholds that websites have to meet in order to get SEO benefits. A website that doesn't pass the Core Web Vitals can drop in search rankings.

This article looks into which of these metrics is hardest to pass and causes the most problems for websites.

Core Web Vitals pass thresholds

Which of the Core Web Vitals is hardest to pass?

The HTTP Archive publishes aggregate data from Google's Chrome User Experience Report (CrUX).

This data shows that the Largest Contentful Paint metric is the hardest to pass. On mobile, less than half of websites provide a good LCP experience at least 75% of the time.

Metric Mobile Pass Rate Desktop Pass Rate
Largest Contentful Paint (LCP) 45.8% 60.3%
Cumulative Layout Shift (CLS) 67.3% 63.6%
First Input Delay (FID) 90.5% 99.9%

The Cumulative Layout Shift metrics is the second hardest to pass. Interestingly, it's also the only metric that's better on mobile than on desktop. Usually performance metrics are worse on mobile devices, as they tend to have less powerful processors and slower network connections. However, this is not the case for CLS as it looks at layout changes rather than load time.

First Input Delay rarely causes sites to fail the Core Web Vitals. Even on mobile only 9.5% of sites fail this metric.

What percentage of sites pass the Core Web Vitals?

Significantly less than half of all websites pass the Web Vitals.

Metric Mobile Pass Rate Desktop Pass Rate
All Core Web Vitals 31.2% 41.1%

However, it is important to keep in mind that Google won't penalize the whole site if Core Web Vitals are poor overall.

Instead, Google puts similar pages on a website into groups and assesses the Core Web Vitals for the group rather than for the whole website.

For example, take a site that contains both a relatively slow interactive JavaScript application and fast interactive content pages. Even if the site as a whole doesn't pass the web vitals, you should still expect the SEO-relevant content to rank well.

The data we looked at in this post all refers to origin-level metrics.

Bonus: First Contentful Paint

First Contentful Paint is a web vitals metric, but it's not one of the Core Web Vitals that impact rankings.

It actually has an even lower pass rate than the Largest Contentful Paint.

Metric Mobile Pass Rate Desktop Pass Rate
First Contentful Paint (FCP) 38.1% 59.5%
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