5 min read By Erwan Goossens
Why your website’s speed affects your sales and your SEO
A slow website loses visitors before they even see your offer. What Google measures, how to test your site for free and what really slows it down.
Your website’s speed affects your sales, because every second of waiting increases the risk that visitors leave before they even see your offer. It also affects your SEO, because Google takes the experience offered to users into account, measured in particular by the Core Web Vitals, when ranking pages. A fast website is not a technical luxury: it is a condition for being found, and then chosen.
What a visitor experiences on a slow website
Picture a customer searching for “plumber Mons” on their smartphone, between two appointments. They tap your website… and wait. A blank screen, an image that appears bit by bit, a button that shifts just as they try to tap it. They go back and choose the next result.
On mobile, the connection is not always good and patience is limited. A slow website also gives an impression of carelessness: if the website is sluggish, what about the service?
What Google measures: the Core Web Vitals
Google assesses visitors’ experience with three indicators called the Core Web Vitals:
| Indicator | What it measures | Good score |
|---|---|---|
| LCP (Largest Contentful Paint) | How long it takes to display the largest visible element, such as the main image or heading | 2.5 seconds or less |
| INP (Interaction to Next Paint) | How responsive the page is when you click or type | 200 milliseconds or less |
| CLS (Cumulative Layout Shift) | How stable the page is: elements that move while it loads | 0.1 or less |
These measurements partly come from real Chrome users: what counts is your website’s real performance, on real phones. Since March 2024, INP has replaced the former FID indicator for measuring responsiveness.
Speed and SEO: what you need to know
Let’s be precise: speed does not replace relevant content. Google first ranks the pages that best answer the search. But page experience is one of the signals taken into account, and it can make the difference between two pages of comparable quality.
Above all, a slow website loses visitors before they read your content. And Google primarily indexes the mobile version of websites: that is the version that needs to be fast. A fast website does not guarantee the top spot, but a slow website penalises itself, with Google as well as with your customers.
How to measure your website’s speed, for free
- PageSpeed Insights (pagespeed.web.dev): enter your website’s address. You get real visitor data, if your site has enough traffic, and a lab diagnosis with suggestions for improvement.
- Google Search Console: the “Core Web Vitals” report sorts your pages into “good”, “needs improvement” and “poor”, on mobile and desktop.
- Lighthouse, built into the developer tools of the Chrome browser: a full audit of performance, accessibility, best practices and SEO.
Always test the mobile version: it is the most demanding one, and it is the one many of your customers use.
The most common causes of a slow website
- Images that are too heavy: a photo of several megabytes displayed at a small size, instead of a resized, compressed image.
- Too many scripts and plug-ins: trackers, share buttons, chat windows, sliders, plug-ins piled up over the years.
- A theme or page builder that is too heavy, loading code for features you don’t use.
- Undersized hosting or poorly configured hosting, without caching or compression.
- Fonts and videos loaded from external services, which add extra connections.
- Elements without reserved space (images, banners), which make the page jump while it loads.
Practical solutions
- Optimise images: modern formats (WebP, AVIF), dimensions suited to the screen, and lazy loading for images further down the page.
- Lighten the code: remove unnecessary plug-ins and only load scripts where they are needed.
- Load third-party services after consent: the page is faster, and it is also a GDPR requirement for non-essential cookies.
- Host your fonts yourself rather than loading them from an external service.
- Enable caching and compression on the server.
- Reserve space for images and blocks so the page does not shift.
- Think mobile first: design the website for a small screen and an average connection, then enrich it for desktop.
Five checks to do this month
You don’t need to be a developer to get started. These checks take less than an hour:
- Test your home page and your most visited page in PageSpeed Insights, in mobile mode, and note the three Core Web Vitals.
- Look at the size of your images: a photo of more than a few hundred kilobytes almost always deserves to be compressed or resized.
- List the plug-ins and scripts installed on your website, and ask yourself which ones are still really useful.
- Open your website on your phone over 4G, away from Wi-Fi: that is the real experience of many of your visitors.
- Check the “Core Web Vitals” report in Google Search Console, if it already contains data for your website.
If your mobile results are poor, start with images and scripts: they are often the quickest and most effective fixes.
Our approach at Novexa Digital
Every website we build aims for a performance score above 90 out of 100 on mobile. The Novexa Digital website is an example: tailor-made code without unnecessary plug-ins, optimised images, fonts hosted on our own server, no analytics script before your consent, and animations that only use properties that are light for the browser.
Is your current website slow? A redesign often lets you start again on a fast foundation, without losing your search rankings. For a shop, speed matters even more: discover our e-commerce website offer.
Frequently asked questions
What is a good loading time?
Aim for an LCP of 2.5 seconds or less on mobile: that is the threshold Google considers “good”. Above 4 seconds, it is rated “poor”.
Is a WordPress website necessarily slow?
No. Slowness mainly comes from the theme, accumulated plug-ins and hosting. A well-built WordPress website can be fast; a poorly maintained website, whatever its technology, often ends up slowing down.
Should you aim for 100 out of 100 in PageSpeed Insights?
It is not essential. A high score is a good indicator, but what counts are your real visitors’ Core Web Vitals and the experience they have. A score above 90 on mobile is an excellent goal.
In short
A fast website keeps your visitors, inspires trust and gives you every chance on Google. Measure your website with PageSpeed Insights, then fix images, unnecessary scripts and page stability first. And if you want a fast website from the start, let’s talk.
