Looking for the latest technical standards? Since 2023, Google has updated its Core Web Vitals to prioritise INP over FID. Click here to read our current guide: Best practices for optimising Core Web Vitals in 2026.
Optimising Core Web Vitals is critical for improving website performance and maintaining search engine visibility. To achieve sustainable results, businesses must look beyond simple speed scores and focus on the technical factors that dictate user experience. In our experience, failing to address these metrics leads to higher bounce rates and missed commercial opportunities.
In May 2021, Google officially incorporated Core Web Vitals as a ranking factor. This update reflects a broader shift toward rewarding websites that prioritise a fast and user-friendly experience. These metrics measure three key pillars: loading speed, interactivity, and visual stability.
Understanding Core Web Vitals in 2023
Google uses a specific set of metrics to quantify the quality of a user experience on a page. To remain competitive, your site must meet or exceed these thresholds:
- Largest Contentful Paint (LCP): This measures loading performance. Specifically, it tracks the time taken to load the largest content element or image on the page. An optimal LCP score is under 2.5 seconds.
- First Input Delay (FID): This measures interactivity. It records the time from when a user first interacts with your site to the time the browser is actually able to respond. A strong FID score is under 100 milliseconds.
- Cumulative Layout Shift (CLS): This measures visual stability. It calculates the frequency and severity of unexpected layout shifts while a page loads. The ideal CLS score is less than 0.1.
Optimising Largest Contentful Paint (LCP)
LCP is often dictated by the largest image or video in the initial viewport. If this element is slow to load, the perceived speed of your site suffers. At Red C, we often find that server-side delays and unoptimised assets are the primary culprits.
- Reduce server response times: High latency can delay every other aspect of the page load. Optimising your code and leveraging efficient hosting environments is essential.
- Compress and optimise media: Images and videos should be compressed and served in modern formats like WebP to reduce payload size without sacrificing quality.
- Implement browser caching: Storing static resources on the user device reduces the amount of data transferred on repeat visits, significantly improving LCP.
Improving First Input Delay (FID)
FID is vital for sites that rely on user engagement, such as those with complex forms or interactive tools. A delay in response time often leads to user frustration and abandoned carts.
- Minimise JavaScript execution: Heavy scripts can block the browser main thread, preventing it from responding to user inputs.
- Defer non-critical scripts: Identify scripts that are not essential for the initial page load and defer them to allow the browser to prioritise interactivity.
- Remove redundant third-party code: Many legacy sites are cluttered with inactive tracking pixels or third-party tools that degrade performance.
Strategic insight: The cost of a delay
We often find that businesses focus solely on the “look” of a site while ignoring the “feel.” A beautiful site that takes 300ms to respond to a click will consistently lose conversions to a simpler, faster competitor. Performance is not just a technical metric: it is a commercial requirement.
Mastering Cumulative Layout Shift (CLS)
Visual stability is critical for user trust. Nothing degrades the user experience more than a page where buttons or text move just as a user is about to click.
- Define image and video dimensions: Browsers require explicit dimensions to reserve space for media before it loads.
- Reserve space for dynamic content: Ads, embeds, and iframes should have pre-defined containers to prevent them from “jumping” into the layout.
- Avoid late-loading fonts: Use font-display: swap to ensure text remains visible and stable while custom fonts are being fetched.
Professional monitoring and attribution
Optimising for Core Web Vitals is an ongoing programme, not a one-off task. We recommend regular audits using Google Search Console and Lighthouse to identify regressions before they impact your ROI. By prioritising these metrics, you ensure your website remains a high-performing asset that supports your broader marketing objectives.
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