Core Web Vitals are the three metrics Google uses to grade real-user page experience:Largest Contentful Paint (how fast the main content shows), Interaction to Next Paint (how fast the page responds when used), and Cumulative Layout Shift (how much the layout jumps around). They are measured from actual Chrome visitors, not lab simulations — which is exactly why so many sites are surprised to be failing.
“what are core web vitals” — 170 searches/mo (Google, US)The thresholds you have to pass
Google publishes exact “good” thresholds, judged at the 75th percentile of visits — meaning at least three-quarters of your real users must land in the good range:
| Metric | Measures | Good | Poor |
|---|---|---|---|
| LCP | Time until the largest content element renders | ≤ 2.5 s | > 4.0 s |
| INP | Latency of interactions across the whole visit | ≤ 200 ms | > 500 ms |
| CLS | How much the layout shifts unexpectedly | ≤ 0.1 | > 0.25 |
Average monthly US search volume. Source: Google autocomplete demand via AnswerThePublic, 2026.
How to fix Core Web Vitals: the working order
Fixing LCP — make the main thing arrive first
On most pages the LCP element is the hero image or headline. Everything that delays it is your fix list:
- Cut server response time. Page caching turns seconds of PHP work into milliseconds of file serving — nothing downstream matters if the HTML itself is slow.
- Optimize the LCP image. Modern format, correct size, compressed — and never lazy-loaded. (Full method: image optimization guide.)
- Get render-blocking CSS and JS out of the way. Inline the critical CSS, defer the rest, and let scripts that don’t paint the first screen wait.
- Preload what the browser can’t discover early — the hero image and the fonts the headline needs.
Fixing INP — stop making the main thread busy
- Delay non-essential JavaScript until interaction or idle: analytics add-ons, chat widgets, and tag-manager payloads are the usual INP killers.
- Break up long tasks. Anything holding the main thread >50 ms delays whatever the user tries next.
- Audit third parties ruthlessly — each embedded script executes on your users’ devices at your metric’s expense.
Fixing CLS — reserve every pixel in advance
- Give images and embeds explicit dimensions so the browser reserves space before they load.
- Never inject banners above existing content — cookie bars and promos belong in reserved slots or overlays.
- Load fonts without layout-shifting swaps — preload the critical ones and use metric-compatible fallbacks.
What to fix first
Do first — high impact, many pages
- Slow server response on top templates
- Lazy-loaded or oversized LCP image
- Render-blocking CSS site-wide
Schedule — high impact, fewer pages
- Third-party script diet (INP)
- Long-task breakup in theme JS
Quick wins — low effort
- Dimensions on images and embeds
- Preload hero image and fonts
- Defer analytics add-ons
Deprioritise — low impact
- Chasing 100/100 lab scores
- Micro-optimising pages with no traffic
Start with the measurement: run the free audit to find the slow-response pages and oversized images dragging your vitals, then work the matrix above top-left first. For the wider speed programme beyond the three metrics, continue with how to speed up a WordPress site.
Frequently asked questions
- What are Core Web Vitals in SEO?
- Core Web Vitals are three field metrics — Largest Contentful Paint (loading), Interaction to Next Paint (responsiveness), and Cumulative Layout Shift (visual stability) — measured from real Chrome users. They feed Google’s page-experience signals, so persistent failures can hold back pages that are otherwise well optimised, and slow pages also convert measurably worse.
- How do I check my Core Web Vitals?
- Three places: Search Console’s Core Web Vitals report shows pass/fail across your whole site grouped by URL pattern; PageSpeed Insights shows field data and lab diagnostics for a single URL; and the Chrome User Experience Report is the raw source behind both. Always judge yourself on field data — lab scores are diagnostics, not the grade.
- What is a good LCP, INP, and CLS score?
- Google’s published "good" thresholds, measured at the 75th percentile of real users: LCP at or under 2.5 seconds, INP at or under 200 milliseconds, and CLS at or under 0.1. Between good and poor sits a "needs improvement" band; the goal is 75% or more of visits in the good range for each metric.
- What replaced First Input Delay (FID)?
- Interaction to Next Paint (INP) replaced FID as the responsiveness Core Web Vital in March 2024. FID only measured the delay before the first interaction was processed; INP measures the latency of interactions across the whole visit, which makes it much harder to pass by accident and much more representative of how the page actually feels.
- How long until Core Web Vitals improvements show up?
- Field data is collected over a rolling 28-day window, so after you ship a fix, the reported numbers improve gradually across roughly a month as new visits replace old ones in the window. Verify the fix immediately with lab tools, then watch the field trend confirm it.