Chrome DevTools can show local Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS) measurements as you load a page, and capture Interaction to Next Paint (INP) when you interact with it. To diagnose a problem, reproduce it in the Performance panel, record a trace, and inspect the browser work and page elements behind the metric. A local result describes the tested browser, device, network and actions—not automatically the experience of all visitors.
What DevTools can tell you—and what it cannot
Chrome for Developers describes the Performance panel this way: “The Performance panel lets you record CPU performance profiles of your web applications.” Its value for Core Web Vitals diagnosis is that it connects a measurement to a timeline of browser activity, such as requests, main-thread work, interactions and layout shifts. A score identifies a symptom; a repeatable trace helps you investigate its cause.
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For a good user experience, Google’s targets are LCP at or below 2.5 seconds, INP at or below 200 milliseconds, and CLS at or below 0.1. These are interpretation thresholds, not guarantees that one local run will match field results.
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Capture a useful Performance recording
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Open the page in Chrome, open DevTools, and select Performance. Check the live LCP and CLS measurements as the page loads.
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Perform the interactions that matter on that page—such as a representative click, tap or keyboard action—so DevTools can capture local interaction data. Use the Interactions and Layout shifts views to relate events and shifts to the timeline.
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If field data is available, enable its display and note the collection period, device class, and whether it is for the origin or the page URL. DevTools provides suggested environment settings; use them to make a local comparison more representative, then reload and repeat the same actions.
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Reproduce the issue consistently and record a Performance trace. Select the event or metric marker of interest and inspect the timeline, network activity and main-thread work around it. The number alone does not explain what caused it.
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Chrome’s interface changes over time. Use the Insights tab within Performance for performance insights; do not look for the old standalone Performance insights panel. Chrome documents that the standalone panel was deprecated and removed starting with Chrome 132. See Performance insights.
Diagnose a slow LCP
In the Performance recording, select the LCP marker or the identified LCP element. Inspect its timing breakdown, then use the trace to determine what delayed that specific element. The four parts help narrow the investigation:
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Time to First Byte (TTFB): time before the response begins. If this portion is large, investigate delays before the browser receives the response.
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Resource load delay: time between the response beginning and the LCP resource starting to load. A large delay points to late discovery or start of the asset; inspect when it becomes discoverable and when its request begins.
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Resource load time: time spent fetching the LCP resource. Check the request and its duration in the network activity.
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Element render delay: time between the LCP asset finishing and the element being painted. Inspect the trace for browser work in that interval.
These are diagnostic categories, not causes by themselves. Verify the explanation against the actual request and timeline rather than inferring a fix from the largest segment alone. The LCP optimization guidance describes the metric and its subparts.
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Find the interaction behind poor INP
INP reflects responsiveness across interactions, so a page-load measurement by itself cannot explain a slow click, tap or key press. Reproduce the particular interaction while recording a trace, then select it in the Interactions view and inspect its timing phases alongside main-thread activity. Look for work that overlaps the interaction and could explain the delay.
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Repeat this with multiple representative interactions and page states. One slow interaction may expose a specific bottleneck, but one interaction is not necessarily representative of every way visitors use the page. The INP optimization guidance explains the metric and its interaction timing.
Trace the layout shifts behind CLS
Open the Layout shifts track in the Performance recording and inspect its screenshots and session windows. Start with the largest session window, then select the shifts to identify which elements moved and what changed around them. The timeline and screenshots help connect a shift to the page state in which it occurred; CLS itself indicates the cumulative impact, not the element or event responsible.
For additional background on interpreting the metric, see CLS optimization guidance.
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Run Lighthouse when you want an automated audit and recommendations. Read its individual metric results and opportunities as evidence to investigate, not as a substitute for field data or a trace of the interaction that produced a real-world problem. A Lighthouse report and a DevTools recording answer related but different questions: the report offers an audit, while the trace shows activity during the scenario you recorded. See Lighthouse overview.
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Make local and field comparisons meaningful
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Compare the same URL or account for the fact that CrUX may show origin-level data instead.
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Compare desktop with desktop and mobile with mobile field data; do not treat them as interchangeable.
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Match the scenario: a page-load result does not diagnose a particular interaction, and a local interaction may not represent all user sessions.
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Keep CPU and network settings in mind when comparing recordings. A change in test conditions can change local results without establishing that the underlying site changed.
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For trends over time, use field data where available rather than treating one local run as a measure of all visitors.
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