Core Web Vitals Update: CrUX vs. PageSpeed Insights (PSI)
CrUX shows how real Chrome users experience your site; PSI adds Lighthouse lab data to diagnose it. Plus the October 2026 experimental soft-navigation metrics for SPA transitions.
- core-web-vitals
- performance
- crux
- pagespeed-insights
- nextjs
- seo
CrUX and PSI are not competing tools. They serve different purposes when measuring website performance.
- CrUX (Chrome User Experience Report) measures how real Chrome users experience your website.
- PSI (PageSpeed Insights) combines real-user data from CrUX with a Lighthouse laboratory test to help diagnose performance issues.
The important distinction is that CrUX provides field data, while PSI provides both field and lab data.
Key differences
| Feature | CrUX | PageSpeed Insights |
|---|---|---|
| Data source | Real Chrome users | CrUX + Lighthouse |
| Data type | Field data | Field + lab data |
| Time period | Rolling 28 days for field data | Rolling 28 days for field data; current simulated lab run |
| Core Web Vitals | LCP, INP, CLS | LCP, INP, CLS from field data |
| Lighthouse score | No | Yes, 0–100 |
| Main purpose | Monitor actual user experience | Diagnose and improve performance |
| Best for | Tracking production trends | Investigating performance problems |
Core Web Vitals thresholds
Largest Contentful Paint (LCP) — loading performance
| Rating | Threshold |
|---|---|
| Good | ≤ 2.5s |
| Needs improvement | 2.5–4s |
| Poor | > 4s |
Interaction to Next Paint (INP) — interaction responsiveness
| Rating | Threshold |
|---|---|
| Good | ≤ 200ms |
| Needs improvement | 200–500ms |
| Poor | > 500ms |
Cumulative Layout Shift (CLS) — visual stability
| Rating | Threshold |
|---|---|
| Good | ≤ 0.1 |
| Needs improvement | 0.1–0.25 |
| Poor | > 0.25 |
Core Web Vitals are evaluated at the 75th percentile of eligible real-user experiences, separately for mobile and desktop.
What's new in 2026?
An important recent change affects React and Next.js applications.
In October 2026, Google announced experimental CrUX metrics that include soft navigations — page transitions in single-page applications that happen without a full browser reload.
This matters for applications using client-side routing because traditional page-load measurements do not fully capture those navigation experiences.
The new experimental metrics cover LCP, INP, and CLS, and are available through CrUX APIs and BigQuery. They are not yet replacements for the standard Core Web Vitals metrics.
Which should you use?
For a production Next.js application, I recommend using both, with different responsibilities.
- CrUX: monitor real-user performance, compare mobile and desktop experiences, and track trends over time.
- PSI: identify performance bottlenecks, investigate slow pages, and validate improvements using Lighthouse diagnostics.
- CrUX History API or CrUX Vis: compare performance before and after deployments rather than relying on a single 28-day snapshot.
A Lighthouse performance score of 95 does not guarantee that a website passes Core Web Vitals. Likewise, a Lighthouse score of 65 does not automatically mean that real users are experiencing poor performance.
You can explore these tools directly through PageSpeed Insights and CrUX Vis.
Bottom line: use CrUX to understand what users actually experience, and PSI to understand what you can improve.