Technical SEO page speed and Core Web Vitals optimisation is among the most critical factors directly affecting Google rankings in 2026. With Google's Page Experience update, it is no longer just content quality but also the experience the user has on the page that is factored into ranking decisions. In this article, we will take an in-depth look at the Core Web Vitals metrics and share the technical methods you can apply to improve your website's performance.
What Are Core Web Vitals and Why Do They Matter?
Core Web Vitals (CWV) are three fundamental performance metrics defined by Google that measure user experience. These metrics measure how quickly the page loads, how quickly it responds to user interactions, and visual stability. The CWV report in Google Search Console shows your site's performance score, based on real user data (field data), on a per-URL basis. Whether a URL falls into the 'Good', 'Needs Improvement' or 'Poor' category directly affects that page's ranking potential. As of 2026, CWV scores continue to be a deciding factor, especially between pages of similar quality.
- LCP (Largest Contentful Paint): The time it takes for the page's largest visible element (usually the hero image or heading) to load. Good score: 2.5 seconds or less.
- INP (Interaction to Next Paint): INP, which replaced FID, measures the response time to all user interactions (clicks, taps, keyboard input). Good score: 200ms or less.
- CLS (Cumulative Layout Shift): Measures the unexpected shifting of elements while the page loads. Good score: 0.1 or less.
PageSpeed Insights and Measurement Tools
Using more than one tool to measure your Core Web Vitals performance paints a more complete picture. Understanding the difference between lab data and field data is also critically important: PageSpeed Insights shows both laboratory (simulated) and real user data, whereas Google Search Console provides only the real user CWV data for your domain.
Analysis with PageSpeed Insights
PageSpeed Insights (PSI) is a free tool that analyses the performance of a specific URL for both desktop and mobile. The PSI report lists, in order of priority, the improvement opportunities beneath the score. The recommendations in the 'Opportunities' section (image compression, JavaScript deferral, caching policy, etc.) contribute directly to LCP and INP improvements. The 'Diagnostics' section, meanwhile, reveals performance obstacles such as long tasks, large DOM size and excessive CSS. An important note: the Lighthouse lab score in PSI and real field performance do not always align; for this reason, be sure to track Google Search Console data as well.
Google Search Console CWV Report
The Core Web Vitals report in Search Console presents how your domain performs according to data collected from real users, grouped by URL. This report can be viewed separately for mobile and desktop devices. Prioritise URL groups in the 'Poor' or 'Needs Improvement' categories and track your improvement work on those pages through the report. It can take up to 28 days for CWV data to be reflected in Google's index, so we recommend being patient after making improvements.
Image Optimisation: WebP and Lazy Loading
Images remain the largest contributor to web page size, and their impact on the LCP metric is enormous. Image optimisation is one of the fastest and highest-ROI ways to improve technical SEO performance.
WebP Format and Modern Images
The WebP format offers 25-35% smaller file sizes compared with JPEG and PNG while preserving image quality. Since all modern browsers support WebP, we recommend converting the static images on all your pages, including e-commerce product images, to WebP. The AVIF format is also finding increasingly widespread use; its compression ratio is superior even to WebP, but browser support is still more limited. With the picture element you can build a structure that automatically selects the appropriate format according to browser support.
Lazy Loading and Preload Strategy
Use the loading='lazy' attribute for images outside the viewport (which the user has not yet seen). This simple method significantly reduces the amount of data downloaded on initial page load and has a positive effect on LCP. However, do not use lazy loading for above-the-fold images (those visible at the top of the screen); instead, add a rel='preload' directive for these images. Preloading your hero image in the HTML head section will directly improve your LCP score.
JavaScript Performance Optimisation
JavaScript is an indispensable component of modern web applications, but when mismanaged it seriously harms both LCP and INP scores. Render-blocking JavaScript and CSS delay the browser's rendering of the page and directly increase LCP.
- Using Defer and Async: Add the defer or async attribute to JavaScript files that are not essential for page rendering. Defer ensures the script runs after the DOM has been parsed, while async downloads the script in parallel and executes it as soon as it is ready.
- Code Splitting: Split large JavaScript bundles into smaller chunks so that only the code needed for that page is loaded. Frameworks such as React, Vue and Next.js support this feature natively.
- Third-Party Script Management: Third-party scripts such as live chat, analytics, advertising and social media widgets can negatively affect your INP value. Load these scripts with a delay (after the load event) or use the facade pattern to avoid loading the real script until the user interacts.
CDN and Server Response Time Optimisation
Server response time (TTFB - Time to First Byte) is a component that directly affects the LCP metric but is frequently overlooked. The target should be to keep TTFB below 800ms. High TTFB values can stem from slow database queries, insufficient server capacity or unoptimised backend code. Using a CDN (Content Delivery Network) improves both TTFB and overall page load speed by serving your static content from the server geographically closest to the user. Cloudflare, Fastly and AWS CloudFront are popular CDN solutions for e-commerce sites.
Shopify Speed Optimisation
While Shopify offers a ready-to-use e-commerce infrastructure, it carries certain constraints when it comes to speed optimisation. The speed problems most frequently encountered on Shopify stores are: unnecessary code weight originating from the theme, a large number of loaded app scripts, and oversized product images. Pay attention to the performance score when choosing your Shopify theme; official Shopify themes such as Dawn are optimised in this respect. Remove apps you are not using and ensure app scripts are loaded only on the pages where they are needed. Using Shopify's built-in image optimisation (Shopify CDN) and uploading images at the correct dimensions also delivers a significant improvement.
Frequently Asked Questions
If my Core Web Vitals score is low, will my ranking drop?
Core Web Vitals is one of Google's Page Experience signals and plays a role as a ranking factor. However, content quality, backlink profile and other SEO factors are still more decisive. A poor CWV score can leave you behind competitors of similar quality; improvement is therefore important, but it should be approached in a planned way without panic.
What is the fastest way to improve LCP?
The methods that deliver the quickest wins in LCP improvement are: converting the hero image to WebP format and preloading it, improving server response time (TTFB), and eliminating render-blocking CSS/JS resources. Sites that apply these three steps typically achieve a 1-2 second improvement in LCP.
What is the difference between INP and FID?
While FID (First Input Delay) measures only the first user interaction on the page, INP (Interaction to Next Paint) evaluates all interactions that occur throughout the life of the page and takes the worst case as its baseline. For this reason, INP reflects the real user experience far better. Google fully replaced FID with INP in 2024.
How can Core Web Vitals be improved on Shopify?
To improve CWV on Shopify, first reduce the number of installed apps and measure each app's impact on page performance. Use a speed-focused theme (Dawn is recommended), upload all images at the correct dimensions and take advantage of Shopify's lazy loading feature. If necessary, use liquid conditions to load app scripts only on the relevant pages.
Conclusion
Technical SEO, page speed and Core Web Vitals optimisation are among the fundamental ways to gain a lasting advantage in Google rankings. Regularly measuring the LCP, INP and CLS metrics and running a systematic improvement process, from image optimisation to JavaScript management, will help you stand out from the competition. Contact Toserof Tech. for SEO and digital marketing solutions.
