For a long time, "speed" meant one thing when it came to websites: how many seconds it took for the page to appear. That was the main thing being measured, and it was a fairly blunt instrument. A page could technically "load" in two seconds while still feeling frustrating to use — images shifting around, buttons that were not ready to be clicked, text that kept moving.
In 2021, Google introduced Core Web Vitals as a more precise way of measuring the actual experience of using a website, not just how quickly files arrived. They became part of Google's ranking algorithm — meaning sites that score well on these measurements are, all else being equal, more likely to appear higher in search results.
There are three Core Web Vitals. Each one measures a different aspect of how a page feels to use.
The First Vital: Largest Contentful Paint (LCP)
This one measures how long it takes for the largest piece of content on your page to appear. Usually that is your main image, a large heading, or a video. It is the moment when a visitor can see the main thing they came to see.
Google considers a good LCP to be 2.5 seconds or less. If it takes longer than 4 seconds, the site is considered to be performing poorly on this measure.
In practical terms, this is most often affected by the size of your images. A photograph straight from a camera can easily be five or ten megabytes. On a website, that same image should ideally be under 200 kilobytes. Compressing and resizing images before they go on your website is one of the most reliable ways to improve your LCP score.
The Second Vital: Interaction to Next Paint (INP)
This one measures how quickly your website responds when a visitor does something — clicks a button, taps a menu, fills in a field. It is about responsiveness. When you press something on a website, how long before anything happens?
Google considers anything under 200 milliseconds (that is, a fifth of a second) to be good. Over 500 milliseconds starts to feel sluggish to most people, even if they cannot quite put their finger on why.
Poor INP scores are usually caused by websites that are running a lot of background scripts — third-party chat widgets, advertising scripts, tracking tools — that all compete for the browser's attention when a visitor tries to interact with the page.
When you press something on a website, how long before anything happens? That is what INP measures.
The Third Vital: Cumulative Layout Shift (CLS)
This one measures how much the layout of a page jumps around while it is loading. You have almost certainly experienced this: you start reading something, then an image loads above the text and everything shifts down, and you lose your place. Or you are about to tap a button and it moves just as you press it.
This is jarring and annoying, and Google measures it precisely. A CLS score of 0.1 or below is considered good. Higher than 0.25 is poor.
Layout shifts are usually caused by images that do not have their dimensions set in the code (so the browser does not know how much space to leave for them before they load), or by fonts that load late and cause text to reflow, or by adverts and embeds that appear after the rest of the page.
Why Should a Small Business Owner Care About Any of This?
The short answer is that Google cares about it, and Google controls whether people find your website or not.
The longer answer is that your visitors care about it too, even if they do not know the technical terms. A page that takes four seconds to load, responds slowly to taps, and shifts around while loading will lose visitors. Most people will not articulate why they left — they will just leave. They will go to the next result on Google instead.
For a local business that depends on search traffic — plumbers, electricians, cleaners, tradespeople, therapists, consultants — a few positions lower in Google's results can mean a meaningful difference in how often the phone rings.
How Do You Check Your Core Web Vitals Score?
Google provides a free tool called PageSpeed Insights. You simply type in your website address, press analyse, and within a few seconds you receive a report with your scores for each vital and a plain-language explanation of what to fix.
The report also distinguishes between "lab data" — a simulation of how the page performs — and "field data" — real measurements from actual visitors to your site. Field data is more meaningful but takes time to accumulate. If your site is new or receives relatively few visitors, you may only see lab data initially.
What Can You Do If Your Scores Are Poor?
The most common and impactful changes are:
- Compress your images. Large, unoptimised images are the most common cause of poor LCP scores. Images should be resized to the dimensions they are displayed at and saved in modern formats such as WebP.
- Remove unnecessary scripts. Every third-party tool you add to your website — chat widgets, booking tools, social media buttons, tracking pixels — adds weight and can slow down how quickly your site responds.
- Set dimensions on images and embeds. Telling the browser in advance how large an image is prevents it from shifting the layout when the image loads. This is a technical fix but a straightforward one for any developer.
- Choose a fast host. Where your website is physically stored affects how quickly it starts sending files to a visitor's browser. Faster hosting providers make a noticeable difference to loading times, and some of the best options are free.
If your website was built recently by a developer who paid attention to performance, it may already be scoring well. If it was built several years ago or assembled using a page builder that adds a lot of extra code, there is a reasonable chance the scores have room for improvement.
The good news is that a site built cleanly from the start — without unnecessary code, with properly sized images, without a heavy stack of scripts — will naturally score well on all three vitals without needing any special tricks. Performance and good craftsmanship tend to go together.