Core Web Vitals are three measurements Google uses to describe how a page feels to real visitors: how quickly the main content appears, how quickly the page responds when you tap or click, and whether things jump around while it loads. They matter for search, but they matter more for people. A slow, jumpy page loses visitors before they read a word.
This guide explains each metric in plain English, what “good” means and what usually fixes problems on small business websites.
The three Core Web Vitals
Largest Contentful Paint (LCP): how fast the main content appears
LCP measures when the biggest thing in the visible part of the page (often the hero image or main heading) finishes appearing. Good: 2.5 seconds or less.
Interaction to Next Paint (INP): how quickly the page responds
INP measures how long the page takes to visibly respond when someone taps a button, opens a menu or types in a form. Good: 200 milliseconds or less. INP replaced an older metric, First Input Delay, as a Core Web Vital in 2024.
Cumulative Layout Shift (CLS): whether things jump around
CLS measures how much content moves unexpectedly while the page loads, such as a button shifting just as you tap it because an image above it finished loading. Good: 0.1 or less.
Google assesses these at the 75th percentile of page loads, separately for mobile and desktop. In practice, the experience has to be good for most visitors, not just those on fast connections.
Lab data versus field data
You’ll see two kinds of numbers:
- Field data comes from real Chrome users visiting your site. It’s what Google uses. Smaller sites often don’t have enough traffic for field data.
- Lab data comes from a test run in a simulated device and network. It’s consistent and useful for diagnosing problems, but it isn’t a real visitor.
Our free speed check reports both where available, along with the specific images, fonts and scripts slowing a page down.
What usually makes small business websites slow
1. Oversized images (the most common cause)
Photos uploaded straight from a camera or phone can be several megabytes each, many times bigger than needed. We see it constantly, including on our own site during a recent clean-up: one large PNG case-study image was 7.4 MB, and the same image as a WebP at a sensible size came to about 0.5 MB, with no visible difference on screen.
Fix: resize images to the size they’re displayed, use modern formats such as WebP, and make sure the hero image isn’t lazy-loaded.
2. Too many plugins, apps and scripts
Every chat widget, slider, pop-up, tracking pixel and social feed adds code. Individually small; together heavy. On Shopify, apps are the usual culprit.
Fix: list everything that loads, remove what you don’t use, and load the rest only where needed.
3. Heavy themes and page builders
Multipurpose themes load code for features you’ll never use. Stacked page builders make it worse.
Fix: a leaner theme or component system, or at least turning off unused features.
4. Slow hosting
Cheap shared hosting can be slow before a single image loads.
Fix: better hosting and page caching. Measure your server response time before and after.
5. Fonts and layout shifts
Web fonts that load late make text flash or jump, and images without set dimensions push content down as they appear.
Fix: preload key fonts, limit the number of font files, and give images and embeds fixed dimensions.
Fixes by metric
| Problem | Usual causes | Usual fixes |
|---|---|---|
| Poor LCP | Huge hero image, slow server, render-blocking scripts | Compress and resize the hero, caching, defer non-essential scripts |
| Poor INP | Heavy JavaScript from plugins, apps and trackers | Remove or delay scripts, simplify interactive widgets |
| Poor CLS | Images without dimensions, late fonts, banners inserted at the top | Set dimensions, reserve space, load fonts properly |
How much do Core Web Vitals matter for SEO?
They’re one signal among many. Google has been clear that relevant, helpful content matters more; a fast page with poor content won’t outrank a slower page that answers the question better. But between similar pages, experience counts, and a faster site almost always converts more of the visitors it gets. Treat speed as a business improvement first and an SEO benefit second.
Speed drifts over time
Most sites launch reasonably fast and slow down as content, plugins and tracking pile up. That’s why regular checks matter. Our CHRISPS Care Growth plan includes a monthly performance review against Core Web Vitals, and our website maintenance guide explains what ongoing care should include.
WordPress and Shopify specifics
On WordPress
- Use page caching and, if your host offers it, server-level caching.
- Audit plugins: page builders, sliders, social feeds and multiple analytics plugins are frequent offenders.
- Make sure images are served at the right size for each screen, not the full original.
- Keep PHP and WordPress current; newer versions are generally faster.
On Shopify
- Apps are the most common cause of slow stores. Uninstalling an app doesn’t always remove the code it added to your theme, so check after removing.
- Choose a well-built theme and avoid stacking customisations on top of it.
- Limit product image sizes and the number of images loaded above the fold on collection pages.
- Be careful with pop-ups and review widgets that load on every page.
Mistakes to avoid when fixing speed
- Chasing a perfect lab score instead of real-world improvement. Field data and real visitors matter more.
- Installing a stack of “speed” plugins that conflict with each other.
- Lazy-loading the main hero image, which delays the largest element and makes LCP worse.
- Fixing only the home page. Your top service, product or landing pages often matter more.
What to do now
- Run your home page and your most important page through the speed check.
- Look at the largest images listed and fix them first.
- List every plugin, app and third-party script; remove what you don’t need.
- Re-test and compare.
If the problems run deeper (an old theme, a struggling server, conflicting plugins), our website rescue service starts with a $199 plan that diagnoses what’s slowing the site and fixes it in priority order. For new builds, our website development includes image, font and script optimisation from the start. You can also run a broader 30-minute website audit yourself.
Written by the CHRISPS studio in Cambridge, Ontario. Thresholds are from Google’s web.dev documentation at the time of writing.