Core Web Vitals optimisation in Lyon — Green Google scores to help you rank higher

What are Core Web Vitals and why does Google care about them?

A Google ranking factor since 2021

Since June 2021, Google has included Core Web Vitals in its ranking algorithm. A fast, stable website is favoured in search results over a slower competitor. This update raised the importance of technical performance for SEO. Lyon small businesses and SMEs that invest in optimising their Core Web Vitals gain a measurable competitive edge in local search results, and this performance directly affects your visibility on Google Business Profile.

LCP — Largest Contentful Paint

LCP measures how long it takes to display the largest visible element on the page (hero image, main heading, block of text). Google considers an LCP under 2.5 seconds good, between 2.5 and 4 seconds in need of improvement, and over 4 seconds poor. The most common causes of a poor LCP: unoptimised images, a slow server (high TTFB), render-blocking CSS and JavaScript, and heavy web fonts.

INP — Interaction to Next Paint

INP replaced FID (First Input Delay) as the official metric in March 2024. It measures the latency of every user interaction (clicks, key presses, taps) during a visit and keeps the worst one. Google’s threshold for a good score is under 200 ms. A high INP is usually caused by heavy JavaScript that blocks the browser’s main thread.

CLS — Cumulative Layout Shift

CLS measures your page’s visual stability: the unexpected shifts that happen when an element moves after the initial load. Google’s threshold is under 0.1. The usual culprits are images without explicit dimensions, web fonts that trigger a reflow, dynamically loaded ads and iframes without dimensions. A poor CLS frustrates users and can drive them away from your site.

How we improve your Core Web Vitals

Image optimisation (WebP, lazy loading, dimensions)

We convert all your images to WebP (or AVIF) with smart compression, add width and height attributes to prevent CLS, and implement native lazy loading for images below the fold. The result: LCP halved on average and CLS brought down to 0.

CSS, JS and HTML minification

Every kilobyte counts. We minify CSS, JavaScript and HTML to reduce the size of transferred files. Tree shaking strips out unused code, and code splitting breaks bundles into chunks loaded on demand.

Deferred loading of third-party scripts

Third-party scripts (analytics, chat, ads, social media) are often the main cause of a poor INP. We load them asynchronously or defer them so they don’t affect the initial rendering of your pages.

Preloading critical resources

We use preload, prefetch and preconnect directives so the browser loads essential resources ahead of time: fonts, hero images, critical stylesheets.

Advanced caching and CDN

Browser caching configured with the optimal lifetime for each type of resource, and deployment on a global CDN to serve your pages from the point of presence closest to your visitors. Pair it with our maintenance plan for lasting performance.

Removing render-blocking JavaScript

We identify any JavaScript that blocks page rendering and remove or defer it. Critical CSS is inlined in the HTML; the rest is loaded asynchronously.

Our results in figures

Target: PageSpeed 90+, results published

Our best projects exceed 95/100 for PageSpeed performance — Damien Mugnier at 97, Compagnie l'Entr'Axes at 98, Le Galant at 96. Not all of them do: the average across our measured projects is 85/100, and every lower score is published on the project page with its cause and a plan to fix it. That is exactly what this service is for. To keep these scores up over time, regular monitoring through our maintenance service ensures consistently optimal performance.

LCP: Google’s threshold is 2.5 s — we aim well below it

We don’t publish an “average LCP”: it depends on each visitor’s network and device, so a single figure would be meaningless. What we do publish are the Lighthouse performance scores for every project, on its case study page — including when there is room for improvement.

CLS: zero layout shift as a design rule

A CLS of zero means no visual shift at all while the page loads. Explicit dimensions on every image, fonts that load without jumping, reserved heights: this is a rule in everything we build, checked with every Lighthouse report — not a figure guaranteed on every project.

Optimised INP on all our recent builds

Thanks to our choice of modern technologies (React, Next.js, Vite) and our attention to code splitting, our sites are built to respond to interactions well within Google’s 200 ms threshold.

Core Web Vitals and your Google ranking in Lyon

What speed changes for rankings

Google uses Core Web Vitals as one ranking signal among others: with equal content, a faster site is crawled more efficiently and converts better. We don’t publish ranking gains we haven’t measured; the Lighthouse scores for each project appear on its case study page, and clients on an ongoing plan receive a monthly rankings report.

The link between speed and conversion rate

According to a Google study on mobile page speed (opens in a new tab), the probability of a bounce increases by 32% when load time goes from 1 to 3 seconds, and by 90% from 1 to 5 seconds. Speed has a direct impact on your conversions, your revenue and your customers’ satisfaction.

Free audit of your current Core Web Vitals

We offer a quick, free check of your current Core Web Vitals. In 15 minutes, we pinpoint your main opportunities for improvement. Go further with a full technical SEO audit or a complete website audit for the full picture.