LCP, INP and CLS in plain English, how to test your website speed in two minutes, and the fixes that make the biggest difference.
You know the feeling. You tap a link on your phone, somewhere between the BTS and the office, and… nothing. A white screen. A spinning circle. Half a picture. By the time the page finally appears, your thumb has already hit back.
Your customers do exactly the same thing to slow websites. And in Thailand, where the vast majority of people browse on their phones — often on mobile data, often on the move — speed isn't a technical detail. It's the difference between a customer and a bounce.
How much does speed really matter?
A widely quoted study by Google found that as page load time goes from one second to three seconds, the probability of a visitor leaving jumps by 32%. Stretch it to five seconds and the odds of a bounce rise by around 90%. Every extra second you make people wait, a slice of them simply leaves.
Speed also affects where you appear. Google uses page experience signals, including a set of measurements called Core Web Vitals, as part of how it ranks pages. A fast site won't outrank better content on speed alone, but between two similar pages, the faster, smoother one has an edge.
Source: Google/SOASTA research on mobile page speed. Numbers show the increase in bounce probability compared with a one-second load.
Core Web Vitals, explained without jargon
Google measures three things about how a page feels to a real person. The names are technical; what they measure is common sense.
LCP — "How long until I see the page?"
Largest Contentful Paint measures how long it takes for the biggest thing on the screen — usually the hero image or the main heading — to appear. Good is 2.5 seconds or less. Over 4 seconds is poor.
INP — "When I tap, does it respond?"
Interaction to Next Paint measures how quickly the page reacts when someone taps a button, opens a menu or types in a form. Good is 200 milliseconds or less; over 500ms feels broken. INP replaced the older FID metric in March 2024.
CLS — "Does stuff jump around?"
Cumulative Layout Shift measures how much the page moves while it loads — the classic moment when you go to tap a link and an ad pushes it down, so you tap the wrong thing. Good is 0.1 or less.
Google looks at the 75th percentile of real visits: three out of four visitors should get a good experience.
Google judges these on real visitors' devices, not on your office Wi-Fi. A site that feels instant on your MacBook can still fail on a three-year-old Android phone on 4G — and that's the phone many of your customers use.
Test your site in two minutes
- Open PageSpeed Insights: go to pagespeed.web.dev and paste in your homepage address.
- Look at the top box first: "Discover what your real users are experiencing" shows field data from actual visitors (if your site has enough traffic).
- Check the Mobile tab: that's the one that matters most for Thai audiences.
- Scroll to "Diagnostics": it lists the specific problems, heaviest first.
- Test your most important pages too: product, booking or contact pages are often slower than the homepage.
If you have Google Search Console set up, its Core Web Vitals report shows which groups of pages pass or fail over time. (If you don't have Search Console yet, set it up — it's free and it's how Google talks to you about your site.)
The usual suspects (and how to fix them)
After auditing a lot of small-business websites in Bangkok, we see the same handful of problems again and again. The good news: fixing the top few usually makes the biggest difference.
1. Huge images
This is the number-one culprit. A 5 MB photo straight from a camera or a stock site, displayed at 800 pixels wide, forces every visitor to download far more than they see. Resize images to the size they are shown, and save them as WebP or AVIF instead of large JPEGs or PNGs. On our own site, converting the photos to WebP cut the image weight from about 7.4 MB to under 1 MB — with no visible difference.
2. Too many plugins and scripts
Every chat widget, tracking pixel, slider, pop-up and "free" plugin adds code that has to download and run before the page responds. Each one seems small; together they are often why INP is poor. Audit them: if nobody has looked at a plugin's data in six months, remove it.
3. Cheap or distant hosting
If your server is slow to respond, everything else waits. Shared hosting packed with thousands of other sites, or a server on the other side of the world with no CDN, can add a second before anything happens. Good hosting with a CDN (a network that serves your files from locations near your visitors) makes a noticeable difference for visitors in Thailand.
4. Web fonts that block the page
Custom fonts look great, but loading five weights of two fonts — plus a separate Thai font — can delay text from appearing. Load only the weights you use, and make sure text shows immediately in a fallback font while the custom one loads.
5. Layout that jumps
Images without set dimensions, late-loading banners and cookie bars that push content down all hurt CLS. Give images and embeds a fixed space before they load, and make pop-ups float over the page instead of shoving it.
6. A page builder doing too much
Drag-and-drop builders make it easy to add sections, animations and effects — and easy to end up with a page that ships megabytes of code for a simple layout. Sometimes the honest fix is a rebuild with lighter technology.
Start at the top — the first three usually deliver most of the improvement.
Speed is a feature your customers feel
Nobody writes a review saying "the website loaded in 1.2 seconds". But they notice when it doesn't. They notice when the menu responds instantly, when the booking form doesn't freeze, when the page doesn't jump. That smooth feeling is a big part of whether a business seems trustworthy online.
Every site we build is designed to load in under a second on a typical phone and to pass Core Web Vitals out of the box — lean code, properly sized images, no unnecessary plugins. If your current site is slow and you're not sure whether to fix it or rebuild it, send us the link and we'll tell you honestly. And if you are planning a rebuild, read how to redesign without losing your Google rankings first.
Frequently asked questions
What is a good load time for a website?
Aim for your main content to appear within 2.5 seconds on a mobile phone (that is Google's "good" LCP threshold). The best small-business sites show the page in around one second.
Does website speed affect Google ranking?
Yes, as one of many signals. Core Web Vitals are part of Google's page experience signals. Relevance and content quality matter more, but speed can decide between similar pages — and it strongly affects whether visitors stay.
Why is my site fast on my computer but slow on my phone?
Phones have slower processors and often slower connections, and PageSpeed Insights tests mobile with a simulated mid-range device on a slower network. Heavy images and scripts hurt much more on phones.
Can I make a WordPress site faster without rebuilding it?
Often, yes: compress and resize images, remove unused plugins, add caching and a CDN, and use a lightweight theme. If the site is built on a heavy page builder with many add-ons, a rebuild can be cheaper than endless tuning.