Core Web Vitals 2026 — what changed and what it means for your site

Core Web Vitals have been a ranking factor since 2021. In March 2024, Google replaced FID (First Input Delay) with INP (Interaction to Next Paint), completing a transition that had been announced a year earlier.

If your site was optimised for Core Web Vitals before that change, it's worth checking whether your INP scores are where they need to be.

What the three metrics actually measure

LCP — Largest Contentful Paint. How long until the main content of the page is visible. For most pages, this is a hero image or large heading. Target: under 2.5 seconds.

INP — Interaction to Next Paint. How long until the browser responds after a user interaction (click, tap, key press). This replaced FID, which only measured the first interaction. INP measures all interactions throughout the page visit. Target: under 200 milliseconds.

CLS — Cumulative Layout Shift. Whether elements move around as the page loads. The classic failure case: you're about to tap a button and an ad loads above it, pushing the button down, and you tap the wrong thing. Target: under 0.1.

Why INP is the new concern

FID was relatively easy to pass — it only measured the delay before the browser started responding to the very first interaction, not how long that interaction took. INP is more demanding: it measures the full time from interaction to visible result, for every interaction on the page.

Pages with heavy JavaScript — particularly single-page applications and pages with lots of third-party scripts — are most likely to struggle with INP. The culprit is almost always "long tasks": chunks of JavaScript that block the main thread for more than 50 milliseconds.

How to check your current scores

1. Go to PageSpeed Insights, enter your URL, and check both mobile and desktop scores.
2. Look at the "Lab data" for CWV pass/fail, and "Field data" (real user data from Chrome) for actual percentile scores.
3. In Google Search Console, check the "Core Web Vitals" report under Experience. This shows real-world data for your actual visitors.

Field data and lab data often differ. Field data is what Google uses for ranking. If lab data says "Good" but field data says "Poor," focus on field data.

Fixing LCP

The most common fix is image optimisation:

• Convert hero images to WebP or AVIF
• Add the priority (or loading="eager") attribute to the above-the-fold image
• Pre-connect to image CDN origins
• Serve images from a CDN close to your visitors

For Next.js sites specifically: the <Image> component handles most of this automatically when configured correctly. Make sure you're using it for all main content images.

Fixing INP

INP improvements are usually about JavaScript. The main approaches:

• Code splitting: load JavaScript only when needed, not all at once
• Removing unused third-party scripts (analytics tools, chatbots, A/B testing tools)
• Deferring non-critical scripts until after main content has loaded
• Moving heavy computation off the main thread with Web Workers

A practical starting point: open Chrome DevTools Performance tab, record a typical user interaction on your page, and look for "Long Tasks" (red bars at the top of the timeline). These are your targets.

Fixing CLS

CLS is usually caused by:

• Images without defined width/height attributes
• Ads or embeds that load and push content down
• Custom fonts causing text reflow (FOIT/FOUT)

Add explicit dimensions to all images. Use font-display: optional or font-display: swap for custom fonts. Reserve space for ads and third-party embeds.

The ranking implication

Passing Core Web Vitals doesn't guarantee rankings. Failing them is a measurable disadvantage, particularly in competitive niches where multiple sites otherwise have similar authority and content quality.

Think of it as a tiebreaker: among equally relevant, equally authoritative sites, the one with better user experience signals (of which CWV is one component) ranks higher.

For businesses where organic traffic is important, Core Web Vitals are worth keeping in "Good" range. We audit them as part of every SEO engagement and fix the underlying issues (not just the symptoms) in our web development work.