Have you ever seen your business website score green on PageSpeed, but visitors still leave before the page finishes loading?
Or maybe you have heard of Core Web Vitals, but you are not sure whether those numbers actually affect sales and conversion?
I understand that confusion. Many business owners focus on lab scores while the thing that really matters is the experience visitors get in the real world.
The two are connected. A slow website does not only frustrate visitors. It can also eat into your revenue little by little.
Amazon found that every 100 milliseconds of loading delay can reduce sales by about 1%. That sounds small on paper, but if your revenue is large, the impact is not.
In Indonesia, the proportion is the same. Imagine an online business with Rp 10 billion in annual turnover. A 2% conversion drop caused by a slow website alone can mean losing about Rp 200 million per year.
What I often see in the field is that business owners do not realize their website is losing opportunities every day, because the problem does not look dramatic on the homepage.
That is why Google introduced Core Web Vitals, a set of metrics that measure website user experience objectively. These are not just technical numbers for developers. They are indicators that correlate directly with business performance: conversion rate, bounce rate, and ultimately revenue.
In this article, I will explain how Core Web Vitals affects your business, with a real case study from our client, PT Zumatic Saka Persada, which improved mobile performance by 75.47%.
Since March 2024, Google officially replaced First Input Delay (FID) with Interaction to Next Paint (INP) as one of the Core Web Vitals. This was not just a technical update. Google adjusted the metric because modern websites are far more interactive than they used to be.
The three pillars of Core Web Vitals:
Data shows that nearly 600,000 websites that previously passed Core Web Vitals suddenly failed when INP replaced FID. INP is stricter about responsiveness, and that ties directly to user experience and conversion rate.
Optimal thresholds for business performance:
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
| LCP | 2.5 seconds or less | 2.5-4.0 seconds | More than 4.0 seconds |
| INP | 200 ms or less | 200-500 ms | More than 500 ms |
| CLS | 0.1 or less | 0.1-0.25 | More than 0.25 |
Although Google says Core Web Vitals is not a dominant ranking factor, John Mueller from Google has said it is “more than just a tie-breaker.” When content and relevance are similar, Core Web Vitals can become the deciding factor.
But in my view, the direct effect on visitor behavior matters more than ranking alone:
Groupe Renault (2024)
After analyzing 10 million visits, Groupe Renault found a strong correlation between Largest Contentful Paint and conversion rate. Every 1 second improvement in LCP contributed to:
Vodafone (2024)
By testing two pages that were visually and functionally identical but differed by 31% in LCP score, Vodafone found:
Now I will walk you through a real project we handled in 2024: PT Zumatic Saka Persada.
Starting point (before optimization):
| Metric | Mobile | Desktop |
|---|---|---|
| Performance Score | 53 | 81 |
| Accessibility | 93 | 98 |
| Best Practices | 96 | 96 |
| SEO | 85 | 85 |
Browser speed test (before):
Results after optimization:
| Metric | Mobile | Desktop | Improvement |
|---|---|---|---|
| Performance Score | 93 | 100 | 75.47% (Mobile) |
| Accessibility | 100 | 100 | 7.53% (Mobile) |
| Best Practices | 100 | 100 | 4.17% |
| SEO | 100 | 100 | 17.65% |
Browser speed test (after):
If you have a technical team, or you simply want to understand what we usually do on projects like this, here is the practical breakdown.
Target: 2.5 seconds or less
Main strategies:
A. Image optimization
<!-- Prioritize the LCP image -->
<img src="hero-image.webp"
fetchpriority="high"
alt="Hero Image"
width="1200"
height="600">B. Critical resource prioritization
C. Hosting and CDN
Upgrading hosting infrastructure can make a clear difference. I usually recommend solid website hosting when you need consistent business performance.
Target: 200 ms or less
Relevant techniques for 2025:
A. Long Animation Frames (LoAF) API
// Monitor long animation frames
if ('PerformanceObserver' in window) {
const observer = new PerformanceObserver((list) => {
for (const entry of list.getEntries()) {
if (entry.duration > 50) {
console.log('Long animation frame detected:', entry);
}
}
});
observer.observe({entryTypes: ['long-animation-frame']});
}B. DOM size reduction
C. JavaScript optimization
Target: 0.1 or less
Practical implementation:
A. Reserve space for dynamic content
.ad-container {
min-height: 250px; /* Reserve space for ads */
width: 300px;
}
.image-placeholder {
aspect-ratio: 16/9; /* Prevent layout shift */
background-color: #f0f0f0;
}B. Font loading optimization
@font-face {
font-family: 'CustomFont';
src: url('custom-font.woff2') format('woff2');
font-display: swap; /* Prevent invisible text */
}C. Proper image dimensions
<!-- Always specify dimensions -->
<img src="image.jpg"
width="400"
height="300"
alt="Description">1. Google PageSpeed Insights
2. Google Search Console
3. Web Vitals Chrome Extension
4. Advanced monitoring
For deeper monitoring needs, you can consider:
John Mueller from Google once said: “It’s not worth over-focusing on tweaking the scores just for SEO. Getting those last few percent can be a ton of work… but it’s not going to make your site’s rankings jump up.”
I agree with that advice. Your focus should be:
Before you start optimizing, I suggest running an audit like the one we did for PT Zumatic:
1. Current state analysis
2. Priority matrix
3. Implementation roadmap
DIY optimization works if:
Professional help makes more sense if:
In PT Zumatic’s case, bringing in professional help produced clear results: not only technical fixes, but also process improvements and long-term planning.
At Harun Studio, we help with Core Web Vitals optimization through several services:
Every website has different challenges and opportunities. What worked for PT Zumatic may need to be adjusted for your site.
Our free performance audit includes:
Contact us for a free consultation. We usually reply on WhatsApp within 10 minutes during business hours, with no obligation to continue.
Do not let a slow website hold your business back. As the PT Zumatic project showed, investing in Core Web Vitals is not just a technical fix. It is a business decision that shows up directly in visitor experience and conversion rate.
Are you ready to evaluate your website and see how much room it still has to improve?
Founder of Harun Studio, web developer, blogger, and hosting reviewer. He helps business owners build healthier websites through design, development, and long-term maintenance.
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