Core Web Vitals

Core Web Vitals are part of Google’s broader Page Experience update, which emphasises that how a website performs is just as important as the content it delivers.

Today we’re announcing that the page experience signals in ranking will roll out in May 2021. The new page experience signals combine Core Web Vitals with our existing search signals including mobile-friendliness, HTTPS-security, and intrusive interstitial guidelines. – Google

The three Core Web Vitals metrics

Google’s Core Web Vitals focus on three key performance areas:

Largest Contentful Paint (LCP) – page speed

LCP measures how long it takes for the largest visible element on a page to load.

This could be a hero image, headline, or video, depending on your site layout. Google aims for an LCP of 2.5 seconds or faster to ensure a smooth user experience.

If your page takes too long to load, users are likely to leave before it finishes, resulting in higher bounce rates and lower engagement.

Common issues affecting LCP:

• Slow server response times
• Large image files
• Render-blocking resources (like JavaScript)

Interaction to Next Paint (INP) – responsiveness

INP has replaced FID as the primary metric for measuring a website’s responsiveness.

INP tracks how long it takes for a website to respond to user interactions, such as clicking a button, tapping a link, or filling out a form. Unlike FID, which measured only the first interaction, INP measures the overall responsiveness across the entire session, providing a more accurate reflection of user experience.

Google’s benchmark for INP:

• Good INP score: Less than 200 milliseconds
• Needs improvement: Between 200 and 500 milliseconds
• Poor INP score: More than 500 milliseconds

If users experience delays when interacting with your site, it can result in frustration and abandonment, especially on e-commerce sites where responsiveness is critical for conversions.

Common causes of poor INP:

• Heavy JavaScript execution
• Long task blocking time
• Slow-loading third-party scripts

Cumulative Layout Shift (CLS) – visual stability

CLS measures how much your page layout shifts unexpectedly as it loads.

Think of how frustrating it is when you’re about to click a button, and suddenly the content moves, causing you to click the wrong link or button. That’s what CLS measures.

Google aims for a CLS score of less than 0.1 to ensure a visually stable experience.

Unexpected layout shifts can frustrate users and make your website feel less trustworthy. This is especially critical for e-commerce sites, where a poor CLS can result in abandoned purchases.

Common issues affecting CLS:

• Images without dimensions
• Ads or embeds that load unpredictably
• Fonts loading late and causing text to shift

Why Core Web Vitals are important for SEO

Google’s mission is to provide users with the best possible experience. That means websites that load quickly, respond efficiently, and remain visually stable are more likely to rank well.

While Core Web Vitals aren’t the only ranking factor, they play a significant role in Page Experience, which influences how Google evaluates your site overall.

Core Web Vitals matter because:

• They impact user satisfaction.
• They reduce bounce rates.
• They can improve conversion rates.

If your site delivers a poor user experience, it’s more likely to see a drop in rankings, especially as Google continues to prioritise these metrics.

How to check your Core Web Vitals scores

There are several tools you can use to check and monitor your Core Web Vitals scores:

What is a “good” Core Web Vitals score?

Google categorises Core Web Vitals scores into three levels:

How to improve Core Web Vitals

Here’s a quick guide on how to improve each Core Web Vitals metric:

Largest Contentful Paint (LCP):

• Optimise images and videos
• Use a Content Delivery Network (CDN)
• Minimise CSS and JavaScript files
• Improve server response times

Interaction to Next Paint (INP):

• Minimise JavaScript execution
• Optimise event handlers
• Use browser caching
• Remove slow third-party scripts

Cumulative Layout Shift (CLS):

• Set size attributes for images and videos
• Preload fonts to avoid late loading
• Avoid inserting new content above existing content

Core Web Vitals aren’t just an official Google ranking factor, they also directly impact how users experience your site. If your Core Web Vitals scores are holding your site back, it’s time to make some changes.