What are Core Web Vitals — and why they cost you real money

You run an ad, someone taps it to see your restaurant’s page, waits five seconds without seeing the menu — and leaves. The click still cost you money. Google has three numbers that measure exactly this kind of thing, together called Core Web Vitals. The name sounds technical, but underneath are three very ordinary questions. In this post I’ll translate each metric into plain words, show why it touches your revenue, and walk you through a free two-minute check of your own site.

What are Core Web Vitals?

Core Web Vitals are the three numbers Google uses to judge whether a page feels pleasant or painful to use. The data comes from real Chrome users visiting your site, so it reflects what your customers actually experience — not a test under ideal conditions.

The three metrics answer three questions: does the main content show up fast, do buttons respond when tapped, and does the layout jump around and cause mis-taps. Let’s take them one by one.

LCP — does the main content show up fast?

LCP (Largest Contentful Paint) measures the time from opening the page to the moment the biggest element on screen appears — usually the food photo, the room photo, or the top banner. Google considers under 2.5 seconds good.

Say a traveler taps your homestay ad to look at rooms. If the sea-view photo shows up within two seconds, they keep browsing. If the screen is still blank at six, most go back to the results and tap the homestay next to yours. You lost them before you got to say anything.

INP — do buttons respond when tapped?

INP (Interaction to Next Paint) measures the gap between a tap and a visible response. Under 200 milliseconds — about a fifth of a second — is good. Past half a second, the page starts to feel frozen.

You’ve probably lived this one: you tap “Book now” on a spa’s page and nothing happens. You assume you missed, tap two or three more times, and either create three duplicate bookings or decide the site is broken and go find another spa. The button did work — it just answered late. To a customer, late means broken.

CLS — does the layout jump around?

CLS (Cumulative Layout Shift) measures how much the content shifts while the page loads. A score under 0.1 is good — in plain terms, the page holds still; text and buttons don’t wander off.

Everyone has hit this: you’re about to tap “View menu” when an image above finishes loading, shoves the whole page down, and your finger lands on a promo banner instead. For the owner, every mis-tap like that is a customer who wanted to see the food and got sent somewhere else.

Why Google uses these numbers for ranking

Google’s business runs on searchers trusting the results. If every result they tap is sluggish and jumpy, they trust Google a little less next time. So for a few years now, Core Web Vitals have been part of the ranking formula: between two pages with equally good content, the smoother one gets to stand higher.

To be fair, it’s not the heaviest factor — content that matches what people search for still matters more. But for competitive searches like “spa in Da Lat” or “beachside homestay in Quy Nhon”, where everyone’s content is decent, speed is often the tiebreaker.

Long before Google penalizes you, a slow site costs you money

Ranking is the side story. The main story is customer behavior: according to Google’s research, when load time grows from 1 to 3 seconds, the probability of a visitor bouncing rises by about 32%. Roughly speaking, two extra seconds of waiting and one visitor in three walks away.

Turn that into money. Say each ad click for your restaurant costs 5,000 dong and you get 100 clicks a day — 500,000 dong. If a slow page makes 30 of those visitors leave before the menu appears, you’re burning 150,000 dong a day on views nobody viewed. Over a month that’s more than four million dong — often more than making the page fast would cost.

A slow site never shows an error. It just quietly lets customers leave before they see the food, the rooms, or the prices.

Check your site in two minutes with PageSpeed Insights

PageSpeed Insights is a free tool from Google. Go to pagespeed.web.dev, paste your site’s address, hit analyze, and wait about half a minute. Nothing to install, nothing technical to learn.

Read the result like a traffic light:

• Green: you pass. Your page isn’t losing customers to speed.
• Orange: it works, but slower than visitors are comfortable with — worth fixing soon.
• Red: you’re losing customers every day; the sooner it’s fixed, the less it costs you.

Two small tips. Check the “Mobile” tab first — most customers of a restaurant, spa, or homestay browse on their phones, and mobile scores usually run well below desktop. And if your site gets decent traffic, the top of the report shows LCP, INP, and CLS measured from real visitors over the last 28 days — those are the numbers to trust most.