Stop 03 · Search Engine Optimization (SEO)Topics · 5/12

Site Speed & Core Web Vitals

In short

People leave slow pages before they even see your offer. Google measures loading, responsiveness and visual stability with Core Web Vitals, and uses them as part of page experience.

Google's specific performance metrics (loading speed, interactivity, visual stability) that are now a direct, measurable ranking factor — a slow site can actively hurt SEO regardless of content quality.

The blob waiter rushes to a table with a menu while holding a steady glass of water.

Think of it like this

A restaurant's first five minutes

How fast the menu arrives, whether the waiter responds when you wave, and whether the table wobbles and spills your water. Three simple things decide your mood. Core Web Vitals check the same three for a webpage.

Watch it happen

The three Core Web Vitals and their 'good' marks

LCP ≤ 2.5 s

INP ≤ 200 ms

CLS ≤ 0.1

1/5Google's three Core Web Vitals, with the thresholds it calls 'good'.

The big ideas

What you need to know

Images are the usual culprit

Compress images, use modern formats like WebP, and size them for the screen.

Reserve space

Set width and height on images and ad slots so the layout doesn't jump.

Fewer heavy scripts

Every chat widget, tracker and popup adds weight. Remove the ones nobody uses.

Test on mobile

Many Indian users browse on mid-range phones and patchy networks. Test like they live.

See it in code

Walk through the code

html

1<img src="/img/hero.webp"2     width="1200" height="600"3     alt="Masala chai being poured">4 5<img src="/img/footer-banner.webp"6     width="800" height="200"7     loading="lazy" alt="Gift box offer">

1/2The hero image loads normally since it's usually the LCP element. Width and height prevent layout shift.

Two small habits that help Core Web Vitals: set image dimensions, and lazy-load images far down the page.

Save yourself the pain

Common mistakes

Oops

Testing speed only on your office Wi-Fi and laptop.

Do this instead

Use PageSpeed Insights, which shows real-user data when available, and test on a mid-range phone.

Oops

Lazy-loading the main hero image.

Do this instead

Lazy-load images lower on the page. The top image should load right away.

Your mission

Score three sites

~20 min

Quick check

A page's text jumps down when an ad loads at the top. Which metric gets worse?

Go deeper

1Run a real website through Google PageSpeed Insights and interpret the Core Web Vitals scores.
2Learn what each vital (LCP, INP, CLS) actually measures in plain language.
3Identify 2-3 common causes of poor Core Web Vitals scores.