Your Ads Are Fine. Your Website Is the Problem.
You've optimized the copy. You've tested the creatives. You've narrowed the audience. The campaign looks great on paper — but the conversions just aren't there.
Before you blame the algorithm, check your website.
Slow, clunky, visually unstable pages are one of the most common and most overlooked reasons that otherwise solid marketing campaigns underperform. And since 2021, Google has made it official: website performance is a ranking signal. It affects your organic visibility, your paid ad quality scores, and directly — through user behavior — your conversion rates.
Core Web Vitals are the framework Google uses to measure that performance. If you're a marketer who has ever seen the term and moved on because it sounded too technical, this article is for you. No jargon. No code. Just what it means, why it matters for your budget, and what to ask your development team to fix.
What Are Core Web Vitals?
Core Web Vitals are three specific metrics Google uses to measure the real-world experience of loading and interacting with a webpage. They were introduced in 2020 and became an official Google ranking factor in 2021.
Think of them as a report card for how your website feels to a visitor — not just how fast it technically loads, but how quickly it becomes usable and how stable it is while loading.
The three metrics are:
LCP — Largest Contentful Paint
What it measures: How long it takes for the largest visible element on the page to fully load. This is usually a hero image, a large heading, or a video thumbnail.
Why it matters: LCP is essentially "when does this page feel loaded?" If your hero image takes 5 seconds to appear, visitors experience 5 seconds of looking at a half-built page — and most of them leave.
- Good score: Under 2.5 seconds
- Needs improvement: 2.5–4 seconds
- Poor: Over 4 seconds
INP — Interaction to Next Paint
What it measures: How quickly your page responds when a user clicks, taps, or types something. INP replaced the older FID metric in 2024 as a Core Web Vital.
Why it matters: If someone clicks your CTA button and nothing happens for a second, they assume the page is broken. Slow interactivity kills trust and conversions, especially on mobile.
- Good score: Under 200 milliseconds
- Needs improvement: 200–500ms
- Poor: Over 500ms
CLS — Cumulative Layout Shift
What it measures: How much the page layout jumps around while loading. If text, images, or buttons move unexpectedly as the page loads, that's a high CLS score.
Why it matters: You've experienced this — you're about to click a button, the page shifts, and you click something else entirely. Or you're reading an article and the text jumps down because an ad loaded above it. CLS measures exactly this, and it's infuriating on mobile.
- Good score: Under 0.1
- Needs improvement: 0.1–0.25
- Poor: Over 0.25
Why Marketers Should Care: The Business Case
This is where it gets real.
It Directly Affects Your SEO Rankings
Since 2021, Core Web Vitals are a confirmed Google ranking factor. A page with poor Core Web Vitals will rank lower than a comparable page with good scores, all else being equal.
For marketers investing in content marketing and SEO, this is critical. You can have the best-written, most thoroughly researched article in your niche — and it will still underperform in search if the page it lives on is slow and unstable.
It Destroys Your Paid Ad Performance
This one surprises most marketers: Google's Quality Score — which determines how much you pay per click and how prominently your ads are shown — is partially based on landing page experience. A slow, poor-performing landing page means:
- Higher cost per click — you pay more for the same ad position
- Lower ad rank — your ads show less frequently and in worse positions
- Lower conversion rates — even the traffic that does arrive converts poorly
A landing page that loads in 1 second versus one that loads in 5 seconds can have dramatically different conversion rates for the same ad spend. You're not just losing SEO traffic — you're paying more to acquire traffic that then bounces before converting.
The Numbers Are Brutal
Studies on page speed and conversion consistently show the same pattern:
- A 1-second delay in page load time reduces conversions by up to 7%
- 53% of mobile users abandon a page that takes more than 3 seconds to load
- Pages that load in 1–2 seconds have conversion rates up to 3x higher than pages that take 5+ seconds
If your site is slow and you're running paid campaigns, you're essentially pouring budget into a leaky bucket. Core Web Vitals fix the leak.
How to Check Your Core Web Vitals Right Now
You don't need a developer to see how your site is performing. Here are three tools any marketer can use:
1. PageSpeed Insights (pagespeed.web.dev)
Enter any URL and get an instant score from 0–100 for both mobile and desktop, with a breakdown of each Core Web Vital. The most important thing: check the mobile score. Most of your traffic is on mobile, and mobile scores are almost always significantly lower than desktop.
2. Google Search Console
If you have Search Console set up for your domain (you should), go to Experience → Core Web Vitals. This shows your real-world data across your entire site — which pages are passing, which need improvement, and which are failing.
3. Chrome DevTools / Lighthouse
More technical, but your developer can run a Lighthouse audit on any page and get a detailed breakdown of exactly what's causing performance issues.
When you check your scores, look at the mobile score first. A desktop score of 95 with a mobile score of 35 is a very common pattern — and the mobile score is what affects the majority of your users and your SEO.
The Most Common Problems (And What to Ask Your Dev Team)
You don't need to fix these yourself. But you do need to know what to ask for.
"Our LCP is too slow"
Likely causes: Large, uncompressed hero images. Slow server response times. Render-blocking JavaScript loading before the main content.
What to ask: "Can we compress and properly size our hero images? Can we lazy-load images that are below the fold? Can we look at our server response time?"
"Our INP is poor"
Likely causes: Too much JavaScript executing when a user tries to interact. Heavy third-party scripts (chat widgets, marketing tools, analytics) blocking the main thread.
What to ask: "Can we audit our third-party scripts and defer anything that isn't critical? Can we look at what's blocking interaction on mobile?"
"Our CLS is high"
Likely causes: Images without defined dimensions (the browser doesn't know how much space to reserve, so content shifts when the image loads). Ads or embeds that load dynamically and push content down.
What to ask: "Can we add explicit width and height attributes to all images? Can we reserve space for ad units so they don't cause layout shifts?"
The Mobile-First Reality Most Marketers Miss
Here's something that should change how you think about your website: Google uses mobile-first indexing. This means Google primarily uses the mobile version of your site for ranking purposes, even for desktop searches.
If your mobile experience is poor — slow LCP, janky layout shifts, frustrating interactivity — you're being penalized in rankings based on that experience, regardless of how good your desktop site looks.
And look at your analytics. For most websites, 55–70% of traffic comes from mobile devices. Your website's performance on a mid-range Android phone on a 4G connection is the experience the majority of your visitors are having.
This is why PageSpeed scores of 90+ on desktop but 35 on mobile are such a common and costly problem. The desktop score feels good. The mobile score is what actually matters.
What Good Performance Actually Looks Like
To make this concrete: at Atom Web Studio, our standard for a production website is:
- Mobile PageSpeed score: 80+ (we typically achieve 85–92)
- Desktop PageSpeed score: 95+ (we typically achieve 95–99)
- LCP under 2.5 seconds on mobile
- CLS under 0.1
- INP under 200ms
These aren't vanity metrics. On a recent HubSpot CMS project, we improved the mobile score from 30 to 88 and the desktop score from 50 to 97. The client's organic traffic improved within weeks of the changes going live — and their paid campaigns saw measurable improvement in quality scores.
A score of 30 on mobile isn't just a bad number. It represents a real experience: users waiting 6–8 seconds for content to appear, layouts shifting as they try to read, buttons that feel unresponsive. That experience drives bounce rates up, conversion rates down, and ad costs higher.
Core Web Vitals and the Broader SEO Picture
Core Web Vitals sit within Google's broader Page Experience signals, which also include:
- HTTPS — your site must be served over a secure connection
- Mobile-friendliness — your site must work well on small screens
- No intrusive interstitials — pop-ups that cover content immediately on page load are penalized
But Core Web Vitals are the most impactful of these signals and the ones most often neglected — because fixing them requires development work, and the conversation between marketers and developers about performance doesn't always happen naturally.
That's the gap this article is trying to close. Marketers need to understand what Core Web Vitals are, why they matter for campaign performance, and how to have an informed conversation with their technical teams about fixing them.
The Action Plan: What to Do This Week
- Run a PageSpeed Insights audit on your five most important pages — homepage, main service/product pages, top landing pages. Note the mobile scores.
- Check Google Search Console for your Core Web Vitals report. See which pages are failing and which are passing.
- Share the results with your development team and ask for a prioritized fix list. If you're working with an agency, ask them specifically about LCP, CLS, and INP on mobile.
- If your mobile score is below 50, treat it as urgent. You are actively losing rankings, paying more for ads, and converting less traffic than you should be.
- Set a benchmark. Agree on target scores with your team (mobile 80+, desktop 95+) and build page performance into your standard QA process for every new page or campaign landing page you launch.
The Bottom Line
Core Web Vitals are not a technical detail for developers to worry about. They are a direct input into your marketing ROI — affecting your SEO rankings, your paid ad efficiency, and your conversion rates simultaneously.
A slow website is a leaky funnel. Every campaign you run, every piece of content you publish, every ad you buy is undermined by poor performance.
The good news: these problems are fixable. Unlike some marketing challenges where the variables are complex and the levers are unclear, Core Web Vitals are measurable, improvable, and directly tied to outcomes you already care about.
Check your scores. Have the conversation with your dev team. Fix the leak.
Tomasz Sygut is a HubSpot CMS Developer and Core Web Vitals specialist at Atom Web Studio. He helps agencies and businesses build fast, high-converting websites engineered for performance from the ground up.
If your PageSpeed scores are letting your marketing down, get in touch — we can help.