What a Perfect 100/100 Core Web Vitals Score Actually Means (and How I Achieved It on My Own Site)

I recently achieved a 100/100 Google Core Web Vitals score on markexcell.co.uk on both mobile and desktop. I am sharing this not simply as a boast, but because a perfect score across both is genuinely uncommon, and because the process of getting there illustrates exactly the kind of technical and design thinking covered in the last article on this blog.

This article explains what Core Web Vitals actually measure, why a perfect score is harder to achieve than people often assume, what I changed to get there, and why this matters for SEO and GEO alike, not just for user experience.

What Are Core Web Vitals, in Plain English?

Core Web Vitals are a set of metrics Google uses to measure real-world user experience on a webpage. They are not abstract technical scores. Each one corresponds to something a visitor genuinely feels when using a website, even if they could not name the metric themselves.

Largest Contentful Paint (LCP)

LCP measures how long it takes for the largest, most prominent piece of content on a page, usually a heading or hero image, to finish loading and become visible. In plain terms, it answers the question: how long does a visitor wait before they see the main thing they came for?

Interaction to Next Paint (INP)

INP measures how quickly a page responds when someone actually interacts with it, clicking a button, opening a menu, tapping a link. It answers the question: does the website feel responsive, or does it feel sluggish and delayed when you try to use it?

Cumulative Layout Shift (CLS)

CLS measures how much content unexpectedly moves around as a page loads. This is the familiar, frustrating experience of trying to tap a button, only for an image or advert to load in above it and shift everything down at the last second. CLS scores this kind of instability.

Why a Perfect Score Is Genuinely Difficult to Achieve

Most websites pass Core Web Vitals reasonably well, particularly on desktop. A genuinely perfect 100/100 score on both mobile and desktop is a different matter, because mobile devices are slower, mobile networks are less reliable, and every inefficiency in a website’s build is magnified under those conditions.

Why mobile is the harder test

• Mobile processors are considerably less powerful than desktop computers, so heavy JavaScript and complex rendering cost more time
• Mobile connections are frequently slower and less consistent, which exposes any unnecessary file size or unoptimised assets
• Smaller viewports make layout shift more noticeable and more disruptive to the user

Many websites that score well on desktop fall short on mobile for exactly these reasons. Achieving a perfect score on both, rather than on one or the other, requires considering the entire build, not just the parts that are easiest to optimise.

What I Actually Did to Reach 100/100

There was no single trick involved. A perfect score is the result of a number of disciplined, fairly unglamorous decisions made consistently throughout the build, rather than one clever fix.

Image handling

• Every image properly sized and compressed for its actual display dimensions, rather than relying on the browser to scale down an oversized file
• Modern image formats used where appropriate, to reduce file size without a visible loss in quality
• Explicit width and height attributes set on images, so the browser reserves the correct space before the image loads, preventing layout shift

CSS and font loading

• CSS kept lean and genuinely necessary, rather than relying on a large, unused framework
• Fonts loaded efficiently, with fallback fonts sized to closely match the final font, again avoiding layout shift as fonts swap in

JavaScript discipline

• JavaScript kept to a genuine minimum, avoiding unnecessary scripts, trackers or plugins that are not earning their place
• Anything non-essential deferred so it does not delay the content a visitor actually came to see

Hosting and delivery

• Reliable, well-configured hosting, since no amount of front-end optimisation fully compensates for a slow server
• Caching and compression properly configured, rather than left at default settings

None of this is exotic. It is the result of treating performance as a genuine priority throughout the build, rather than as an afterthought to be addressed once the site is otherwise finished.

Why This Matters for SEO and GEO, Not Just User Experience

As covered in the previous article on this blog, page speed and technical quality are not purely a user experience concern. They are a genuine ranking factor for traditional search, and a trust signal that AI systems take into account when deciding what to cite.

The direct SEO connection

Google has confirmed Core Web Vitals as part of its ranking considerations for some years. A consistently fast, stable website is treated more favourably than a slow, unstable one, all else being equal.

The GEO connection

AI systems are more able to crawl, parse and trust a website that loads quickly and reliably. A page that struggles to render consistently is harder to crawl efficiently and is one of several quality signals that can make a system more cautious about treating it as a reliable source.

The credibility connection

There is also a simple, honest point worth making here. If a business offering web design and search optimisation services cannot get its own website’s technical foundations right, it is reasonable for a prospective client to question it. A perfect score on my own site is, among other things, a demonstration of the standard I work to.

A Practical Checklist for Improving Your Own Score

You do not need a perfect score to see meaningful benefit. Use this list as a starting point to improve your website’s Core Web Vitals.

☐  Run your website through Google’s PageSpeed Insights to see your current scores and specific issues flagged

☐  Check whether your images are properly sized and compressed for how they actually display

☐  Add explicit width and height attributes to images to prevent layout shift

☐  Review font loading and check for visible font-swap shift as the page loads

☐  Audit JavaScript and remove or defer anything not genuinely necessary

☐  Check your hosting performance, particularly under real-world mobile conditions

☐  Re-test on mobile specifically, not only desktop, since this is where most sites fall down

Frequently Asked Questions

Is a 100/100 Core Web Vitals score actually rare?

Yes, particularly across both mobile and desktop simultaneously. Many websites achieve a good desktop score reasonably easily, but mobile conditions expose inefficiencies far more readily, which is why a genuinely perfect score on both is a meaningful technical achievement rather than a routine one.

Do I need a perfect score to benefit from this?

No. Meaningful ranking and user experience benefits begin well before a perfect score is reached. Most websites would see a genuine improvement simply by addressing the most common issues, oversized images, layout shift and unnecessary JavaScript, without needing to chase a perfect result.

Does a high Core Web Vitals score guarantee good rankings?

No. Core Web Vitals are one of many ranking factors, alongside content quality, backlinks and relevance. A fast, stable website with weak content will not outrank a strong, well-optimised competitor purely on speed. The two need to work together.

How often should I check my Core Web Vitals scores?

A check every few months is sensible, particularly after adding new plugins, scripts, images or design changes, since any of these can quietly undo previous performance work without it being obvious from looking at the page itself.

Can I achieve this on a WordPress website, or do I need something custom-built?

A high score, including a perfect one, is achievable on WordPress, provided the theme, plugins and hosting are all chosen and configured carefully. WordPress itself is not the limiting factor. Unnecessary plugins, bloated themes, and poor hosting are far more likely to be the actual cause of poor scores.

Want Your Own Site Reviewed?

If you would like an honest assessment of where your own website currently stands on Core Web Vitals, and what would genuinely move the needle, get in touch for a straightforward conversation with no obligation and no sales pitch.