Website speed and Core Web Vitals: why it genuinely matters
A slow website costs you customers and rankings. Here's how Core Web Vitals work, what usually slows sites down, and how to fix it.
In short
Core Web Vitals, meaning LCP, INP and CLS, measure how fast and stable a website feels to visitors and factor into Google's rankings: slow load times and shifting pages cost conversions and rankings, and the most common causes, heavy images, unoptimised code and slow hosting, all have concrete fixes.
What Core Web Vitals actually are
Core Web Vitals are three metrics Google uses to assess the user experience of a page: Largest Contentful Paint (LCP), Interaction to Next Paint (INP) and Cumulative Layout Shift (CLS). Together they give an objective picture of how fast and stable a page feels to a real visitor, rather than just a technical load time.
These metrics matter because they don't only affect how pleasant a website feels, they also factor into how Google ranks websites in search results.
The three metrics explained
A page that scores well on all three feels fast and reliable to visitors. Poor scores often lead to frustration, such as clicking the wrong button because the page just shifted, or leaving before the content is even visible.
- LCP (Largest Contentful Paint): how quickly the largest visible element, usually a hero image or heading, loads. Target: within 2.5 seconds.
- INP (Interaction to Next Paint): how quickly the page responds to a click or tap. Target: under 200 milliseconds.
- CLS (Cumulative Layout Shift): how much the page unexpectedly shifts while loading. Target: under 0.1.
Why speed affects both rankings and conversion
Google uses page speed as one of many ranking factors, particularly on mobile. A slow site is no longer just a minor drawback, it's a concrete disadvantage compared with faster competitors in the same search results.
Beyond SEO, the impact on conversion is at least as important: visitors drop off increasingly quickly the longer a page takes to load, especially on mobile, where patience is even shorter. Every second of delay costs potential customers, regardless of how good your product or service is.
Common causes of slow websites
- Overly large, unoptimised images and videos
- Too much or poorly loaded JavaScript and third-party scripts
- Slow or overloaded hosting
- Too many plugins on CMS platforms such as WordPress
- Fonts and adverts that load late and cause the page to shift
- No caching or content delivery network in use
Practical fixes that make the biggest difference
Not every fix requires a full rebuild. A few targeted changes often deliver a noticeable improvement, especially around images and third-party scripts.
- Compress and optimise images, use modern formats such as WebP
- Lazy load images and videos below the fold until they're needed
- Reserve space for images and adverts so the page doesn't shift
- Reduce the number of third-party scripts, such as unnecessary tracking tools
- Use caching and a content delivery network for faster delivery
- Choose fast, reliable hosting suited to your traffic
How to measure speed and Core Web Vitals
Several free tools show exactly where the bottlenecks lie. Google's PageSpeed Insights and the Chrome Lighthouse panel provide both lab data and, where available, real-user data via the Chrome UX Report. Google Search Console also shows the Core Web Vitals status of your entire site, grouped by issue.
| Tool | What it measures | When to use it |
|---|---|---|
| PageSpeed Insights | LCP, INP, CLS and concrete improvement tips | Checking individual pages |
| Lighthouse (Chrome) | Full performance audit including best practices | Deeper technical analysis |
| Search Console | Core Web Vitals status site-wide | Overview and trends over time |
| Chrome UX Report | Data from real visitors | Validating actual user experience |
Speed isn't a one-off project
Website speed isn't something you fix once and forget. New content, extra plugins or a new marketing tool can drag performance back down. Check periodically, especially after major changes to the site.
For businesses investing heavily in ads or SEO, this matters even more: a slow landing page undermines the return on every euro spent driving traffic there.
Frequently asked questions
What are Core Web Vitals in plain terms?
They're three metrics Google uses to judge how fast and stable a webpage feels to visitors: how quickly the main content appears, how quickly the page responds to clicks, and how stable the page stays while loading.
Does website speed really affect my Google ranking?
Yes, page speed is one of the ranking factors, particularly on mobile. It's not the most decisive factor, but among pages with similar content and authority, a faster site can have an edge over a slower competitor.
What's the fastest way to speed up my website?
Start by optimising images, as they're often the biggest culprit. Compress files, use modern formats and only load images when they're needed. This alone often delivers a noticeable improvement without a full rebuild.
How often should I check my website's speed?
Check at least a few times a year, and immediately after major changes such as a redesign, new plugins or a new marketing tool, as these can unintentionally slow the site down.
Can I measure Core Web Vitals myself without technical knowledge?
Yes, free tools such as Google PageSpeed Insights give you an instant score with concrete, plain-language improvement suggestions. Google Search Console is also useful for a full picture across your site.
Updated: 20 July 2026