Core Web Vitals in 2026: what actually moves conversion
Key takeaways
- A page passes when LCP is 2.5s or less, INP 200ms or less and CLS 0.1 or less for 75% of real visits.
- INP replaced First Input Delay in March 2024 and measures every interaction, not just the first.
- A 0.1 second faster mobile journey lifted retail conversion by 8.4% (Deloitte for Google, 2020).
- Fix the pages that make money first: hero image, third-party scripts, reserved space and long JavaScript tasks.
Core Web Vitals are three measurements Google uses to judge how a page feels to real visitors: how fast the main content appears, how quickly the page responds when you tap something, and whether the layout jumps around. Passing them helps rankings a little. Fixing them properly helps conversion a lot.
What are the three Core Web Vitals?
Google scores each metric at the 75th percentile of real visits over 28 days, so three in four visitors need a good experience before a page passes.
| Metric | What it measures | Good | Poor |
|---|---|---|---|
| LCP (Largest Contentful Paint) | When the main image or headline appears | 2.5s or less | Over 4s |
| INP (Interaction to Next Paint) | How quickly the page reacts to taps and clicks | 200ms or less | Over 500ms |
| CLS (Cumulative Layout Shift) | How much the layout moves while loading | 0.1 or less | Over 0.25 |
INP replaced First Input Delay as a Core Web Vital in March 2024. That change caught a lot of sites out, because FID only measured the first tap. INP measures every interaction on the page, including the slow filter, the laggy menu and the "Add to cart" button that takes a second to respond.
Does page speed really change conversion?
Yes, and the effect shows up in money, not just rankings. In a 2020 study commissioned by Google, Deloitte measured mobile sites across Europe and the US and found that a 0.1 second improvement across the whole journey raised conversion rates by 8.4% for retail and 10.1% for travel sites.
Our own numbers point the same way. When Harbor & Pine Dental came to us, their mobile pages took 4.8 seconds to load and 0.9% of visitors booked an appointment. Twelve weeks later the pages loaded in 0.9 seconds and the booking rate was 3.4%. Speed wasn't the only change (online booking replaced a phone number), but nobody books on a page they abandoned.
Which fixes move revenue, and which are vanity
Here's where we disagree with a lot of audit reports. A Lighthouse score of 100 on your homepage is pleasant. It's also mostly irrelevant if your pricing page and checkout are slow. Fix the pages where money changes hands first.
Fixes that usually pay off
- Serve the hero image properly. On most slow sites the LCP element is one oversized photo. Resize it, serve AVIF or WebP, give it explicit dimensions and load it first. This alone often takes a full second off LCP.
- Cut third-party scripts. Chat widgets, heatmaps, three analytics tags and a forgotten A/B testing script will wreck INP. Audit every tag, remove what nobody reads and load the rest after the page is usable.
- Reserve space for anything that loads late. Cookie banners, ads, embedded reviews and web fonts cause most layout shift. Give them a fixed slot.
- Break up long JavaScript tasks. If tapping a filter freezes the page, the main thread is busy. Splitting that work is the most reliable way to fix a poor INP.
Work that rarely changes the bottom line
- Shaving 50ms off a page that already passes all three metrics.
- Chasing a perfect lab score while real-user data (the numbers Google actually uses) is fine.
- Rebuilding a whole site on a new framework when two templates are the real problem.
How to check your own site in ten minutes
- 01Open Google Search Console and go to Core Web Vitals. This shows real-user data, grouped by similar pages.
- 02Sort by "Poor" URLs on mobile. Note which templates they belong to (product, blog, landing page).
- 03Run one example of each template through PageSpeed Insights and read the "Diagnose performance issues" section.
- 04Rank the fixes by how much traffic and revenue each template carries, not by how bad its score looks.
Where this matters most
If most of your buyers come from paid mobile traffic, every slow second is money you already spent. That's why every site we ship is held to Core Web Vitals at launch; our median mobile load time at launch is 0.9 seconds. See how we approach website development and conversion optimisation, or take the two-minute assessment to see where your site stands.
