Google grades every page on your site with three numbers. They are called Core Web Vitals, and they influence your search visibility, your ad landing page experience, and whether visitors stick around long enough to convert.
Most explanations of these metrics are written for developers. This one is written for marketers. Here is what each number means, when it matters for revenue and when it is vanity, why marketing sites in particular get slow, and how to check yours without paying for anything.
The three metrics in plain language
Core Web Vitals measure three things a real visitor feels. How fast the page shows its main content. How fast it responds when tapped. How much it jumps around while loading.
That is it. Three feelings, three numbers.
Largest Contentful Paint (LCP)
LCP measures how long it takes for the biggest thing on the screen to appear. On most marketing pages that is the hero image or the headline.
Google's published target is 2.5 seconds or less. Past that, visitors are staring at a blank or half-built page and deciding whether to wait.
Think of LCP as the answer to one question. How long until the visitor sees the thing they came for?
Interaction to Next Paint (INP)
INP measures how quickly the page reacts when someone taps a button, opens a menu, or types in a form field. It replaced an older metric called First Input Delay in 2024, so older articles may reference the wrong one.
Google's target is 200 milliseconds or less. A page can load fast and still feel broken if every tap takes a beat to register.
If LCP is about the first impression, INP is about whether the page feels alive once someone starts using it. Forms are where this bites hardest, and forms are where your leads come from.
Cumulative Layout Shift (CLS)
CLS measures how much the page moves around while it loads. You know this one by feel. You go to tap a link, a banner loads above it, the page jumps, and you tap the wrong thing.
Google's target is a score of 0.1 or less. The score itself is abstract. The experience is not. A jumpy page feels cheap, and it produces misclicks on the exact buttons you care about.
When speed matters, and when it is vanity
Not every point of improvement is worth chasing. Here is the honest split.
Speed matters when it is bad enough to feel. A page that takes five seconds to show its hero is losing people, especially on mobile, especially on paid traffic where you already paid for the click. Moving that page from failing to passing is real work with real payoff.
Speed becomes vanity once the page already feels instant. Grinding a lab score from the low nineties to a perfect 100 will not change what a visitor experiences. If your Core Web Vitals already pass Google's thresholds, your growth problem lives somewhere else. Spend the effort there.
One more distinction that saves a lot of confusion. There are two kinds of data.
- Lab data is a simulated test run on demand, like the Lighthouse score everyone screenshots.
- Field data is what real visitors actually experienced in Chrome over the past 28 days.
Google evaluates your site on field data. A great lab score on your office wifi means little if real visitors on phones are having a slow experience. Always look at the field numbers first.
Why marketing sites get slow
Marketing sites have a particular set of habits that hurt these numbers. Most of them are operational, not technical.
The script pile-up
Open a typical tag manager and you find years of history. Analytics, heatmaps, session recording, chat widgets, A/B testing tools, and a pixel for every channel the team has ever tested.
Each one is a small program the visitor's phone must download and run. Tools get added for a campaign and never removed. Nobody owns the cleanup. This is the most common cause we see, and it hits INP hardest.
Oversized images
A designer exports the hero image at full resolution, someone uploads it, and now every visitor downloads a file sized for a billboard to view on a phone. This is the classic LCP killer.
The fix is not one resize. It is a process, so the next upload does not repeat the mistake.
Builders and themes
DIY builders like Wix and Squarespace are fast to launch and template-driven, and the template loads code for every feature it supports, whether your page uses it or not. On WordPress, every plugin can add its own scripts and styles, and quality varies widely by theme and shop.
None of this makes builders a bad choice. It means the platform decision has a speed cost that someone should be watching.
Fonts, popups, and embeds
Custom fonts that load late and swap in cause layout shift. So do popups, cookie banners, and announcement bars that push content down. Embedded videos and social feeds pull in heavy third-party code for a small piece of the page.
How to check for free
You do not need a paid tool for any of this.
- PageSpeed Insights at pagespeed.web.dev. Paste a URL. The top section shows field data from real Chrome users. That is the section that matters. The diagnostics below it tell you what to fix.
- Google Search Console. The Core Web Vitals report shows which groups of pages pass and fail across the whole site, on mobile and desktop separately.
- Chrome DevTools. Right click any page, choose Inspect, open the Lighthouse tab, and run a report for lab diagnostics.
Two habits make these checks useful instead of decorative.
First, test your money pages, not just the homepage. Your top paid landing pages and your key service pages are where speed touches revenue.
Second, judge yourself on mobile numbers. That is where most of the slow experiences live and where Google focuses.
Slow sites are usually an operations problem
Here is the pattern behind almost every failing score we review. Nobody owns the tag manager. There is no process for images. No one looks at the field data until rankings dip or cost per lead climbs.
That is not a design problem. It is an operational one, and it is fixable.
This is how we approach websites at Citamark. We design, build, and host sites wired for conversion, with the measurement and cleanup built into how the site runs, not bolted on later. A standalone website audit covers speed alongside tracking and conversion paths, and our website and automation builds put a system around the things that decay, like scripts and images.
If you are not sure whether speed is your real bottleneck or just the most visible symptom, that is exactly what the Performance Audit is for. We look at the whole layer, from page speed to tracking to the accounts sending traffic, and hand you a prioritized plan you keep either way.