Do real Chrome users see your pages load fast, respond quickly, and stay stable?
Core Web Vitals measure live user experience; AI agent browsers fail when these scores are poor.
What this signal tests
We check three Google-defined Core Web Vitals against real Chrome users over the last 28 days, measured at the 75th percentile. Largest Contentful Paint (LCP) tracks how fast the main content appears. Interaction to Next Paint (INP) tracks how snappy clicks and taps feel. Cumulative Layout Shift (CLS) tracks how much the page jumps around as it loads.
Why it matters for your visibility in AI
Agentic browsers - ChatGPT Atlas, Perplexity Comet, Claude for Chrome, OpenAI Operator - drive real Chromium with strict per-action timeouts. If your LCP is four seconds, an agent waiting for content to appear may time out before clicking the button it was asked to click. If your CLS is high, a button moves between when the agent decides to click and when it actually clicks, hitting the wrong element entirely. The practical consequence is that AI agents asked to book your demo, add your product to cart, or extract a price from your page silently fail. The user blames the agent, the agent blames the site, and your conversion never happens.
Pass criteria at a glance
| Criterion | Passes when |
|---|---|
| LCP p75 <=2500ms AND INP p75 <=200ms AND CLS p75 <=0.10. |
How we test it
We query Google's Chrome User Experience Report API, which aggregates anonymous timing data from real Chrome users who opt in. We read your domain's 75th percentile values for LCP, INP, and CLS over the trailing 28-day window. If any one of the three is in the poor range, the signal fails, since Google's pass definition requires all three to be good at the same time.
Show technical detection method
POST to https://chromeuxreport.googleapis.com/v1/records:queryRecord; read p75 of LCP/INP/CLS metrics. Requires Cloud API key (free, 150 QPM).
If your site fails: how to fix it
- Fix LCP by preloading your hero image with link rel=preload and fetchpriority=high, server-side rendering above-the-fold content, and serving compressed image formats like AVIF or WebP through a CDN such as Cloudflare Images or Vercel Image.
- Fix INP by breaking up long JavaScript tasks, deferring non-critical scripts with the defer attribute, and removing third-party tags (chat widgets, heavy analytics) from the critical path.
- Fix CLS by always declaring width and height attributes on images and iframes, reserving space for ads and embeds before they load, and using font-display:optional or font-display:swap with a matched fallback metric.
- Verify changes have rolled out by checking PageSpeed Insights and the CrUX dashboard. Field data updates over a 28-day rolling window, so improvements take a few weeks to fully reflect.
- If your site is too low-traffic for CrUX data, focus on the Lighthouse lab score instead and use synthetic monitoring to track regressions.
Quick facts
| Maturity | ESTABLISHED |
|---|---|
| Weight | high |
| Category | Performance |
Primary sources
Related signals
Frequently asked questions
What if my site has no CrUX data?
CrUX requires a minimum traffic threshold from Chrome users. Low-traffic sites are not reported, in which case AI crawlers and agents fall back to lab-based estimates. We recommend running the Lighthouse lab performance check (see related signals) as a substitute.
Will fixing this also improve my Google ranking?
Yes. Core Web Vitals are a documented Google ranking factor, applied at the page level since 2021. Improving them benefits both your traditional search rankings and your visibility to agent browsers driven by AI assistants.
How long do changes take to show up?
CrUX uses a 28-day rolling window, so improvements take several weeks to fully reflect in the field data. You can verify changes immediately using Lighthouse lab tests in Chrome DevTools or PageSpeed Insights.
Which metric should I fix first?
Usually LCP, because it touches the most code paths and tends to drive the biggest single improvement. INP is next; it often catches up once heavy JavaScript is deferred. CLS is typically a few targeted fixes (image dimensions, font loading) rather than systemic work.
Run your own scan
Run a free scan and see how your site grades across all 155 AI-readiness signals.