Improve SEO and UX with Core Web Vitals: a Practical Guide to Faster Sites

Website loading speed has a major impact on both SEO and UX. Core Web Vitals are key web-performance indicators proposed by Google, and their importance is only increasing in 2024 and beyond. A slow site frustrates users, lowers rankings, and increases abandonment.

This article covers practical techniques from the basics of Core Web Vitals to explanations of the major metrics LCP, FID, and CLS, along with how to measure them using tools such as PageSpeed Insights and Search Console and how to improve them in concrete ways.

Start optimizing Core Web Vitals now to improve SEO and UX and turn your website into a stronger success.

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What are Core Web Vitals? A detailed look at their effect on SEO and UX

Why Core Web Vitals matter in 2024 SEO and modern UX

Core Web Vitals are website performance indicators proposed by Google. They measure three aspects of how users experience a web page: loading speed, interactivity, and visual stability. In other words, they evaluate whether a site is actually delivering a good user experience.

In 2024 SEO, Core Web Vitals have become even more important. Google increasingly emphasizes user-centered search experiences and tends to rank sites that deliver a comfortable web experience more highly. In practical terms, optimizing Core Web Vitals is now essential SEO work.

We strongly recommend that site owners improve Core Web Vitals so they can rank better in search results and deliver a better overall user experience.

Core Web Vitals are one of the factors that Google’s core ranking systems consider, along with other page-experience signals, when determining rankings.

Core Web Vitals and Google Search results

A strong UX improves user satisfaction and directly supports business success through better conversion rates, more repeat visitors, and a stronger brand image.

Understand the three main metrics: LCP, FID, and CLS

Core Web Vitals consist of the following three metrics. Let’s look at what each one represents in concrete terms.

• LCP (Largest Contentful Paint): the time it takes until the main visual content on the page, such as a large image, video, or text block, is displayed. Because it represents when users can recognize the main content, it is a crucial indicator of loading speed. The target value is 2.5 seconds or less.
• FID (First Input Delay): the time between a user’s first interaction, such as clicking a link or pressing a button, and the browser’s response. It measures how quickly the page becomes responsive to user action. The target value is 100 milliseconds or less.
• CLS (Cumulative Layout Shift): how much unexpected layout movement occurs while the page is being displayed. For example, if an image loads late and suddenly pushes text downward, that is layout shift. A high CLS can cause accidental clicks and damages UX. The target value is 0.1 or less.

The close relationship between Core Web Vitals and user experience

Core Web Vitals are closely tied to user experience.

For example, if product images take too long to appear on an ecommerce site, or buttons respond slowly when clicked, users may become frustrated and leave. On the other hand, when pages load quickly and interactions feel smooth, users can shop comfortably and are more likely to make a purchase.

What happens when Core Web Vitals are poor? Ranking risk and higher abandonment

Poor Core Web Vitals can hurt Google rankings. In particular, if you want to rank for competitive keywords, optimization is indispensable.

Sites with poor Core Web Vitals also tend to have higher abandonment rates. When pages are slow or hard to interact with, users feel stress and leave.

A higher abandonment rate can lower conversion rates and damage brand perception. For example, if a site with one million monthly page views sees a 10 percent increase in abandonment, the resulting annual loss can easily amount to tens of millions of yen.

How to measure Core Web Vitals with free tools

Measure Core Web Vitals with Google PageSpeed Insights

PageSpeed Insights is a free web-page analysis tool provided by Google. By simply entering a URL, you can measure many performance indicators, including Core Web Vitals. It can analyze both mobile and desktop performance and gives concrete recommendations for improvement, which makes it extremely practical.

1. Open the PageSpeed Insights website.
2. Enter the URL you want to analyze and click the analyze button.
3. After a short wait, you will see scores and detailed analysis results for both mobile and desktop.
4. Review both field data and lab data to understand the current situation. Field data is based on measurements from real users, while lab data is collected in a simulated environment used by PageSpeed Insights.

Use Search Console to identify pages with problems

Google Search Console is a free tool for website owners. Its Core Web Vitals report helps you understand site-wide performance. Because it lists problematic URLs, you can identify which pages need improvement and decide what to prioritize.

1. Log in to Google Search Console.
2. Choose Core Web Vitals from the menu on the left.
3. Select either the mobile or desktop report.
4. Click a problematic URL to review detailed information.

How to use the Chrome “Web Vitals” extension for real-time measurement

The Chrome extension called Web Vitals is a convenient tool that lets you measure Core Web Vitals in real time while browsing a page.

You can install it for free from the Chrome Web Store. After installation, the Web Vitals icon appears in the Chrome toolbar. When you open a page, the icon shows LCP, FID, and CLS values so you can watch performance changes in real time.

It is especially useful for debugging pages during development.

Use Lighthouse for deeper performance analysis

Lighthouse is an open-source automated tool for auditing web-page quality. It is built into Chrome DevTools and can measure many performance indicators, including Core Web Vitals.

Beyond performance, it can also evaluate a page from angles such as accessibility, SEO, and best practices. You can run Lighthouse from developer tools or use it as a Node.js module. Because it generates detailed reports, it is excellent for finding concrete areas to improve.

Advanced measurement with the web-vitals npm package

web-vitals is a JavaScript library for measuring Core Web Vitals. It is provided as an npm package and can be embedded directly into JavaScript code.

Using web-vitals lets you collect more detailed measurement data and perform custom analysis. For developers, it is a useful way to understand Core Web Vitals more deeply and design more appropriate improvements.

Analyze Core Web Vitals and performance in detail with GTmetrix

GTmetrix is a powerful tool for analyzing web-page performance. It measures a wide range of indicators, including Core Web Vitals, and provides detailed reports for identifying performance problems. Because it also incorporates PageSpeed Insights and Lighthouse data, it enables analysis from multiple angles.

GTmetrix shows not only loading speed but also page size, request count, waterfall charts, and more. That helps you identify bottlenecks and choose effective improvements. The free version is often sufficient, while the paid version adds deeper analysis and monitoring features.

1. Open the GTmetrix website.
2. Enter the URL you want to analyze and click Analyze.
3. After a short wait, review the results.
4. Use the Summary tab to check the major performance indicators, including Core Web Vitals.
5. Use the Performance tab to review detailed analysis and identify improvements.
6. Use the Structure tab to find structural issues in the page.
7. Use the Waterfall tab to visualize resource loading and locate bottlenecks.

Because GTmetrix provides a viewpoint that differs from PageSpeed Insights and Lighthouse, using them together leads to more effective performance optimization. It is especially helpful when you need to pinpoint bottlenecks and consider concrete fixes.

★ Learn GTmetrix in one minute: how to use it and what to check

How to improve Core Web Vitals

Improve LCP with image optimization and by removing render-blocking resources

The main ways to improve LCP are as follows.

• Optimize images: reducing image file sizes shortens load time. Using next-generation formats such as WebP and compressing images to the right size can reduce file size significantly.
• Remove render-blocking resources: if resources such as CSS and JavaScript block page rendering, LCP can worsen. Removing unnecessary resources or applying deferred loading can reduce that blocking effect.
• Use a CDN: by delivering content from servers distributed around the world, a content delivery network can shorten load times.

Improve FID with JavaScript optimization and fewer unnecessary tasks

The main ways to improve FID are as follows.

• Optimize JavaScript: when JavaScript processing takes too long, FID can worsen. Optimizing code and avoiding unnecessary script execution can improve responsiveness.
• Reduce unnecessary tasks: long-running tasks reduce browser responsiveness. Breaking tasks into smaller pieces or using Web Workers for background processing can improve FID.
• Optimize third-party scripts: if external service scripts are hurting FID, review how they load or consider alternatives.

Improve CLS with image sizing and font optimization

The main ways to improve CLS are as follows.

• Specify image dimensions: when width and height are set on images, the browser can reserve the right amount of space before loading and prevent layout shift.
• Optimize font loading: if fonts take too long to load, text rendering can be delayed and create layout shift. Using properties such as font-display can improve CLS.
• Reserve space for ads and embedded content: ads and embeds can also trigger layout shift, so define their dimensions appropriately in advance.

Specific techniques you can apply right away

Image optimization best practices

Image optimization is a major factor in improving LCP. Here are some concrete techniques.

• Use WebP: WebP is a next-generation image format developed by Google. It usually offers smaller file sizes than JPEG or PNG while maintaining strong visual quality, so use it where browsers support it.
• Use image-compression tools: tools such as TinyPNG and ImageOptim can significantly reduce file size while preserving acceptable quality.
• Use responsive images: by using srcset and sizes, you can deliver images that fit each device’s screen size better.
• Use lazy loading: delaying the loading of images outside the viewport can speed up the initial display. The loading=\"lazy\" attribute makes this easy to implement.

On WordPress, image optimization can often be improved easily by installing a plugin.

★ Five WordPress plugins that dramatically improve speed and the measures that matter

Use browser caching effectively

When you use browser caching, resources that have already been loaded can be stored in the browser and reused on subsequent visits. That can improve loading speed significantly.

To enable caching, you need to set appropriate HTTP headers on the server side. For example, Cache-Control headers can be used to define how long resources remain valid.

Speed up delivery with a CDN

A CDN, or Content Delivery Network, is a distributed server network spread across the world. By using a CDN, you can deliver content from servers that are closer to the user and reduce loading time.

The impact is especially large for sites with many visitors coming from overseas.

★ What is a CDN? Improve speed and performance with a distributed server network

Optimize JavaScript and CSS

Reducing the file size of JavaScript and CSS and optimizing how they load can improve both LCP and FID.

• Minify files: removing unnecessary spaces and comments reduces file size.
• Defer loading: if JavaScript or CSS blocks rendering, delaying those resources can speed up the initial view.
• Split code: dividing large JavaScript files into smaller chunks and loading only what is needed reduces the initial download volume.

Improve server response time

Server response speed directly affects LCP. The following measures are effective for improving response time.

• Choose a fast server: using high-performance hosting can improve response speed.
• Use server-side caching: caching database queries and API responses can reduce server load and improve response speed.
• Optimize the database: optimizing queries reduces the time needed to retrieve data.

We measured server speed directly to find out which hosting services are actually fast.

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Core Web Vitals and mobile friendliness

Mobile browsing continues to grow every year, which means mobile friendliness is no longer optional. Core Web Vitals matter on mobile too, and mobile performance optimization directly supports both SEO and UX.

Why mobile-first indexing makes mobile optimization essential

Google uses mobile-first indexing, meaning the mobile version of a page is treated as a primary factor in determining rankings.

Google continues to recommend that webmasters create mobile-friendly content.

Google evaluates all content indexed for a site, both desktop and mobile versions, to determine how well it supports mobile.

Rollout of mobile-first indexing

In other words, poor Core Web Vitals on mobile can negatively affect rankings. It is important to adopt responsive design and provide a fast, comfortable web experience on mobile devices as well.

Deliver the best mobile experience with responsive design

Responsive design is a web-design approach that uses a single HTML source to support many screen sizes. By using CSS media queries to adjust layout and content based on the screen, you can provide optimal display across PCs, tablets, and smartphones.

If you can support both environments with one site, you can keep canonical URLs, avoid complex redirects, and make shared web addresses simpler.

Responsive web design and the power of media queries

Responsive design is a basic requirement for mobile friendliness and also helps improve Core Web Vitals.

Should you consider AMP for ultra-fast delivery?

AMP, or Accelerated Mobile Pages, is a framework for displaying mobile pages at high speed.

By using specialized AMP HTML and restricting JavaScript execution, it can dramatically improve page-load speed. AMP pages can also be delivered through Google’s cache servers, allowing even faster display.

However, AMP has functional limitations, so it is not suitable for every website.

AMP itself does not directly strengthen SEO rankings.

Whether a site includes valid and displayable AMP pages does not affect rankings in search results at all.

The difference is that when a site includes AMP pages, an AMP icon may be added in search results.

Eight tips for implementing AMP on client websites

The latest on Core Web Vitals and what comes next

Google algorithm updates and Core Web Vitals

Google updates its algorithms regularly, and Core Web Vitals are part of that evolving landscape. It is important to keep checking Google’s official blog and developer documentation so you can stay current and adapt to algorithm changes.

Looking ahead, the importance of web-performance metrics is expected to increase even further.

Web-performance metrics to watch beyond Core Web Vitals

There are many web-performance metrics beyond Core Web Vitals. For example, TTI (Time to Interactive) and TBT (Total Blocking Time) have also been suggested as indicators that may matter more in future updates to Core Web Vitals.

It is important to understand these metrics as well so that you grasp the bigger picture of web performance.

Frequently asked questions about Core Web Vitals

What are the target values for Core Web Vitals?

• LCP: 2.5 seconds or less
• FID: 100 milliseconds or less
• CLS: 0.1 or less

If you meet these target values, the page is considered good.

What if improving Core Web Vitals is difficult?

Improving Core Web Vitals can require changes to site structure and technical knowledge. If it is difficult to improve things on your own, consider consulting a web-performance specialist or consultant.

How do Core Web Vitals relate to other SEO measures?

Core Web Vitals are one important element of SEO, but they are most effective when combined with other SEO efforts. Content SEO, keyword strategy, and link building should also be implemented in balance to achieve stronger overall results.

Summary

Core Web Vitals are essential performance indicators for modern websites. To deliver an excellent user experience and win strong rankings in SEO, it is important to understand and optimize the three metrics of LCP, FID, and CLS.

Keep watching the latest developments and adapt to evolving web technologies. That is what leads to website success. Take action now and use Core Web Vitals optimization to build a site that works better for both users and search engines.