How To Improve Core Web Vitals Without Hurting User Experience

To improve Core Web Vitals, you need to minimise loading delays while maintaining a smooth user experience. This involves optimising images, enabling browser caching, and reducing unnecessary scripts that slow down your pages.

At DevelopersDex, web performance sits at the centre of every site we build and maintain. We regularly work across projects to identify where these Core Web Vitals issues hide and which fixes truly move the ranking. So here’s what we’ll explain in this guide:

• Why Google’s ranking signals factor them in
• How to fix each one without breaking your site
• Some tools that surface your real field data

Let’s start by answering what Google’s Core Web Vitals are.

What Are Google’s Core Web Vitals?

Google’s Core Web Vitals are a set of metrics that measure real-world user experience across three performance domains: LCP, INP, and CLS. They sit within Google’s broader quality signals for how pages are ranked.

The Core Web Vitals metrics cover these distinct areas of site performance:

• Largest Contentful Paint (LCP): This vital metric tracks how long the largest visible element on a web page takes to fully load, such as an image, a text block, or a video thumbnail. The good threshold is 2.5 seconds or under.
• Interaction to Next Paint (INP): Google retired their First Input Delay (FID) and replaced it with INP in 2024. It measures how long each key interaction takes on a page and reports the slowest one. In this case, anything at or under 200 milliseconds passes, and higher values indicate areas that may need optimisation.
• Cumulative Layout Shift (CLS): Visual stability is what this metric is built around. Late-loading web fonts and unsized ads push this score up, so a result under 0.1 is the target. It basically scores how many page elements move unexpectedly as content loads.

The 75th Percentile Rule: All three web vitals metrics need to score “Good” for at least 75% of user visits. Just one underscored metric, and the whole Core Web Vitals assessment will fail with it.

Is the Core Web Vitals Worth Your Time?

Google confirmed Core Web Vitals as an official part of its page experience ranking signals back in 2021. Since then, they’ve been an important ranking signal alongside content quality and backlinks as Core Web Vitals ranking factors.

However, the fixes don’t always work the way most site owners need them to.

In fact, during our SEO work, we rarely see a failed assessment caused by a single metric. More often, it’s a combination of loading performance, visual stability, and responsiveness that drags a site’s scores down together.

What’s more, Google uses these web vitals as a tie-breaker as well. When two pages are closely matched on content quality and authority, the one with stronger metrics tends to edge ahead in search engine results (and that smallest gap is where rankings get lost).

But improvement isn’t as difficult as it sounds. The most notable jump in search engine rankings comes from pulling a page out of “Poor” into “Good.” Chasing progress beyond that threshold, though, delivers very little extra ranking benefit.

How Do You Fix Each Core Web Vitals Problem?

Each metric has a specific root cause, and fixing that cause is what moves the score. Most site owners we’ve seen treat symptoms rather than sources (which is why their site’s goals take longer than they should).

Here are the four most effective fixes that would also keep your UX stable.

1. Speed Up LCP With Image Priority Fixes

The LCP element, usually the main image or largest block of text, is almost always the first place to check when the Largest Contentful Paint is slow.

By default, browsers treat most images as low priority, so they queue behind other critical resources during the initial load. In this scenario, adding fetchpriority=”high” directly to the LCP image signals the browser to load it ahead of competing resources.

Another good way is to convert images to WebP or AVIF, which reduces page size without any visible quality loss. This gives the browser less to download before the LCP element renders.

2. Cut INP by Reducing JavaScript Execution

Long tasks on the main thread are the leading cause of poor interaction with next paint scores. When JavaScript execution runs uninterrupted, user interactions queue up behind it, and input is delayed.

Breaking those long tasks into smaller chunks gives the browser room to process interactions in between (that’s where most of the gains come from).

Deferring third-party scripts like analytics tools, chat widgets, and A/B testing code reduces the load on the main thread, too. Moving heavy computations to Web Workers takes that further by running unused code off the main thread entirely.

3. Prevent CLS With Reserved Space Attributes

Cumulative layout shift climbs when visual elements load without predefined dimensions. This pushes content shifts through the page as each one appears. For instance, images, iframes, and ad slots are some of the most frequent offenders.

Setting explicit width and height attributes on every image and video element lets the browser reserve space before the asset downloads. That way, layout shifts stop before they start. For injected content like banners or dynamic blocks, reserving space in the layout ahead of time follows the same logic.

Pro Tip: Use the “aspect-ratio” CSS property. It keeps visual stability intact across different screen sizes without locking layouts into fixed pixel values.

4. Use Critical CSS to Remove Render-Blocking

Across the WordPress sites we work on, render-blocking CSS is one of the first things we look at. Inlining critical CSS (the code needed to render above-the-fold content) directly inside the <head> lets the page display straight away without waiting for external stylesheets.

By contrast, you can defer non-critical CSS using media attributes, such as:

• media=“print”
• media=“screen” (for screens; monitors, phones, tablets)
• media=“(max-width: 768px)”
• media=“(min-width: 1024px)”

These attributes shift the elements to load after the initial paint.

Server-side rendering paired with minified CSS and JS files brings the page size down further, which cuts the time before the browser even begins rendering.

Tools That Show Your Real Core Web Vitals Data

Not every tool that claims to measure Core Web Vitals data is drawing from the same source. Some rely on simulated conditions, while others pull from real user monitoring.

Below are the additional tools that can show your Google Core Web Vitals performance across different data types:

Google Search Console and Google PageSpeed Insights are where most site owners start, and for good reason. They show the field data that feeds into Google’s ranking signals, rather than the lab scores that tools like Lighthouse or Chrome DevTools produce.

That distinction is worth keeping in mind every time a Lighthouse audit shows a clean bill of health, but Search Console is still flagging poor web vitals metrics. These tools show metrics differently depending on the source. That’s why we recommend cross-referencing field data against lab data.

Quick Note: After using the “Validate Fixes” feature, allow a full 28 days before checking Google Search Console for updated results.

Your Core Web Vitals Won’t Fix Themselves

All three Core Web Vitals connect directly to how real users experience your site. Together, LCP, INP, and CLS influence whether Google marks your website’s performance as passing.

By optimising loading speed, minimising layout shifts, and reducing interaction delays, you can improve both page performance and visitor satisfaction. Along with that, consistent monitoring and targeted improvements will make Core Web Vitals your strength rather than a test to ace.

If you’re ready to go further, DevelopersDex has more articles covering web performance, page speed, and everything in between. Check out our website and implement the strategies to optimise your pages.