Real User Performance Intelligence
Core Web Vitals Monitoring with Lab and Real-User History
Compare current Lighthouse evidence with public Chrome real-user Core Web Vitals history when available, including LCP, INP, CLS, mobile and desktop context, and supported trend interpretation.
Beacon separates lab and field evidence so a one-time test is not presented as the complete experience of every visitor.
Current lab
Use controlled Lighthouse evidence to investigate the page under the conditions of the current test.
Public field history
Use eligible CrUX History data to review rolling real-user trends over approximately 40 weekly periods.
Interpretation
Compare mobile, desktop, lab, and field evidence while keeping scope, availability, and uncertainty visible.
Core Web Vitals monitoring needs lab and field context
A current lab test and a real-user field dataset answer different questions. Lighthouse runs a controlled test that helps diagnose the page under specific conditions. Chrome UX Report data summarizes eligible real Chrome user experiences from the public CrUX dataset. One can reveal a current technical weakness while the other can show whether a pattern appears across real visits over time.
NAVINES Beacon keeps these evidence types separate. When public CrUX history is available, it can place current lab observations beside mobile, desktop, and aggregate field history and explain where the evidence agrees, differs, improves, or degrades.
The performance metrics Beacon can place in context
Google defines the current Core Web Vitals as LCP, INP, and CLS. Beacon can also display FCP and experimental TTFB diagnostic history when those metrics are returned by the CrUX History API.
Largest Contentful Paint (LCP)
Loading experience based on when the largest visible image, text block, or video is rendered. Google's good threshold is 2.5 seconds or less at the 75th percentile.
Interaction to Next Paint (INP)
Field responsiveness across user interactions. Google's good threshold is 200 milliseconds or less at the 75th percentile.
Cumulative Layout Shift (CLS)
Visual stability based on unexpected movement of visible page content. Google's good threshold is 0.1 or less at the 75th percentile.
First Contentful Paint (FCP)
A diagnostic metric for when the first text or image content is painted. It adds context but is not one of the three current Core Web Vitals.
Time to First Byte (TTFB)
A diagnostic measure of initial server response timing. CrUX labels the returned history metric as experimental.
75th percentile (p75)
Google assesses Core Web Vitals at the 75th percentile, separately for mobile and desktop where data is available.
How NAVINES Beacon interprets real-user history
The CrUX History API provides weekly collection periods, and each period represents an overlapping rolling 28-day aggregate. Beacon normalizes the returned periods, separates overall, phone, and desktop evidence, calculates supported trends, and compares field context with current lab evidence.
A weak lab result with healthy field history can justify controlled retesting before a large remediation. Poor field history with a better current lab result may mean the latest test is not yet representative of users or that an improvement has not flowed through the rolling dataset. Agreement between weak lab and field evidence creates a stronger reason to investigate.
What to do when CrUX data is unavailable
CrUX does not contain sufficient public data for every origin or page. Eligibility, traffic, privacy thresholds, and requested scope affect availability. An unavailable response is not a website failure and should not become a negative finding by itself.
Beacon continues with current Lighthouse and other supported website evidence when public field history is unavailable. Teams can also use authorized first-party real-user monitoring when they need private, page-specific, or more immediate performance detail.
From public URL to verified follow-up
STEP 1
Test the page
Collect the current supported lab performance evidence.
STEP 2
Request public history
Query aggregate, phone, and desktop CrUX scopes where Google has sufficient data.
STEP 3
Compare evidence
Review p75 metrics, trends, and agreements or differences between lab and field.
STEP 4
Investigate and recheck
Prioritize supported actions, implement approved work, and verify with both evidence types over time.
Scope and limitations
CrUX represents eligible Chrome users and overlapping 28-day aggregates; it is not a complete census of every visitor. Lighthouse is a controlled test and cannot measure real-user INP in the same way as field data. Beacon does not guarantee data availability, diagnose every root cause, or modify the website.
Primary technical sources
Core Web Vitals Monitoring FAQ
What are the current Core Web Vitals?
The current Core Web Vitals are Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability.
What is the difference between Lighthouse and CrUX?
Lighthouse is a controlled lab test. CrUX is aggregated field data from eligible real Chrome users. The two sources can differ because devices, networks, interactions, pages, and collection periods differ.
Does Beacon show mobile and desktop Core Web Vitals?
When the public CrUX History API returns sufficient data, Beacon can organize overall, phone, and desktop evidence separately.
How often does CrUX History update?
Google states that CrUX History updates weekly. Each point represents an overlapping rolling 28-day collection period.
Why can Core Web Vitals data be unavailable?
Not every origin or URL meets CrUX eligibility and privacy thresholds. Unavailable field data does not mean the site failed a Beacon scan.
Does Beacon guarantee a Core Web Vitals fix?
No. Beacon provides evidence and AI-guided investigation context. Authorized developers still need to diagnose, implement, test, and verify approved changes.
Put performance evidence in the right context
Review current website performance, add public real-user history when available, and turn supported evidence into a safer investigation and verification plan.