A slow website quietly costs you money. Visitors leave before the page appears, Google pushes you down the results, and your ads cost more for less. The good news is that speed is measurable, and most of the problems are fixable.
Google measures page experience with three metrics called Core Web Vitals. Here is what they mean, what scores to aim for, and how to improve them.
What are Core Web Vitals?
Core Web Vitals are three measurements of how a real visitor experiences your page:
| Metric | What it measures | Good score |
|---|---|---|
| LCP, Largest Contentful Paint | How fast the main content (usually the hero image or headline) appears | 2.5 seconds or less |
| INP, Interaction to Next Paint | How quickly the page responds when someone taps, clicks or types | 200 milliseconds or less |
| CLS, Cumulative Layout Shift | How much the layout jumps around while loading | 0.1 or less |
INP replaced the older First Input Delay (FID) metric in March 2024, which made responsiveness much harder to fake. A page can look loaded but still feel sluggish if heavy JavaScript blocks every tap.
Google assesses these scores using data from real Chrome users, and a page passes when at least 75% of visits meet the "good" threshold.
Do Core Web Vitals affect SEO?
Yes. Core Web Vitals are part of Google's page experience signals. Great content still matters most, but when two pages are similarly relevant, the faster, more stable page has the edge. More importantly, speed affects what happens after the click:
- Visitors are far more likely to leave a page that takes several seconds to load, especially on mobile data.
- Layout shifts cause mis-taps and frustration, which hurts trust and form completions.
- Faster pages tend to convert better, so every visitor you already paid for is worth more.
How to check your website's Core Web Vitals
- PageSpeed Insights (pagespeed.web.dev): enter any URL to see real-user data and lab diagnostics.
- Google Search Console: the Core Web Vitals report groups your pages into Good, Needs improvement and Poor.
- Chrome DevTools Lighthouse: useful for testing changes before they go live.
Always check the mobile results. That is where most sites struggle and where most of your visitors probably are.
10 practical ways to improve Core Web Vitals
1. Compress and resize images
Oversized images are the most common cause of slow LCP. Serve modern formats like WebP or AVIF, and never load a 4000-pixel image into a 400-pixel space.
2. Prioritise the hero image
Make sure the largest element above the fold loads first: don't lazy-load it, and give it a high fetch priority. Lazy-load images further down the page instead.
3. Use fast hosting and a CDN
A slow server delays everything. Good hosting with a content delivery network serves your pages from locations close to each visitor, which matters if you have clients in different countries.
4. Cut unused JavaScript and plugins
Every slider, chat widget, tracking script and page-builder add-on adds weight. Audit what you really use. On WordPress sites, plugin bloat is often the single biggest INP problem.
5. Break up long tasks
For INP, heavy JavaScript that runs for hundreds of milliseconds blocks the page from responding. Split work into smaller chunks and defer anything not needed immediately.
6. Reserve space for images, ads and embeds
Set width and height (or an aspect ratio) on images, videos and ad slots so the browser keeps space for them. This is the main fix for CLS.
7. Load fonts carefully
Self-host fonts, use only the weights you need, and use font-display: swap so text appears straight away.
8. Cache and pre-render pages
Static or pre-rendered pages load almost instantly. Modern frameworks like Next.js can generate pages ahead of time and serve them from the edge.
9. Avoid layout-shifting banners
Cookie notices and promotional bars that push content down cause CLS. Overlay them instead, or reserve their space from the start.
10. Re-test after every change
Speed drifts as sites grow. Check your Search Console report monthly and test new pages before launch.
When is it time to rebuild instead of patching?
If your site runs on an old theme or page builder, has dozens of plugins, and still fails on mobile after the obvious fixes, patching can cost more than a rebuild. A modern, well-built site gives you speed, better SEO foundations and an easier site to manage.
Frequently asked questions
What is a good PageSpeed score?
Aim for 90+ on mobile in PageSpeed Insights, but focus on passing the real-user Core Web Vitals (LCP, INP and CLS), because those are what Google uses.
Why is my site fast on desktop but slow on mobile?
Phones have slower processors and often slower connections, so heavy images and JavaScript hurt far more on mobile. Always optimise for mobile first.
How long does it take for Google to notice speed improvements?
Core Web Vitals use a rolling 28-day window of real-user data, so improvements usually show in Search Console within about a month.
The bottom line
Speed is one of the few ranking factors you fully control, and it pays off twice: better visibility on Google and more enquiries from the visitors you already get. Mistique Designs builds fast, mobile-first websites and runs SEO audits that fix what's slowing you down. Get a free quote and we'll review your site's Core Web Vitals.