---
title: "Core Web Vitals - Serpwise Documentation"
description: "Measure LCP, INP, CLS, and other real-world performance signals through Google PageSpeed Insights with historical tracking."
url: "https://serpwise.ai/docs/core-web-vitals/"
source: "https://serpwise.ai/docs/core-web-vitals/"
---
[Back to Serpwise](/)

Serpwise Documentation

Connect · Configure · Execute

Search documentation

`/`

No documentation found.

↑↓ Navigate Enter to open

Browse documentation

**Core Web Vitals** lets you measure real-world performance for any crawled page using the **Google PageSpeed Insights API v5**. Get Lighthouse scores, detailed metric breakdowns, and historical trends for both mobile and desktop - all from within Serpwise.

* * *

## Overview

Serpwise integrates with the PageSpeed Insights API to provide on-demand performance measurements. Each measurement runs a full Lighthouse analysis and returns:

- Core Web Vitals metrics (LCP, INP, CLS)
- Additional performance metrics (FCP, TTFB, SI, TBT)
- A composite performance score (0-100)
- Optimization opportunities and diagnostics
- Both **mobile** and **desktop** results

Historical measurements are stored so you can track performance trends over time.

* * *

## Metrics

Each measurement captures the following metrics with Good / Needs Improvement / Poor thresholds:

| Metric                              | Good    | Needs Improvement | Poor       | Description                                    |
|-------------------------------------|---------|-------------------|------------|------------------------------------------------|
| **LCP** (Largest Contentful Paint)  | ≤ 2.5s  | ≤ 4.0s            | > 4.0s  | Time until the largest visible element renders |
| **INP** (Interaction to Next Paint) | ≤ 200ms | ≤ 500ms           | > 500ms | Responsiveness to user interactions            |
| **CLS** (Cumulative Layout Shift)   | ≤ 0.1   | ≤ 0.25            | > 0.25  | Visual stability - how much the layout shifts  |
| **FCP** (First Contentful Paint)    | ≤ 1.8s  | ≤ 3.0s            | > 3.0s  | Time until the first content renders           |
| **TTFB** (Time to First Byte)       | ≤ 0.8s  | ≤ 1.8s            | > 1.8s  | Server response time                           |
| **SI** (Speed Index)                | ≤ 3.4s  | ≤ 5.8s            | > 5.8s  | How quickly content is visually populated      |
| **TBT** (Total Blocking Time)       | ≤ 200ms | ≤ 600ms           | > 600ms | Total time the main thread was blocked         |

Each metric is color-coded: green (good), amber (needs improvement), or red (poor).

* * *

## Measuring a Page

1. Navigate to any [URL Detail](/docs/pages-overview) page
2. Click the **Performance** tab
3. Click **Measure** to run a PageSpeed Insights analysis

The measurement takes a few seconds to complete. Results appear for both mobile and desktop once the analysis finishes.

* * *

## Historical Trends

Every measurement is stored, building a history of performance data for each URL. The Performance tab shows:

- **Line charts** for each metric over time
- **Mobile vs. desktop** comparison on the same chart
- **Trend indicators** showing whether performance is improving or regressing

Use historical data to verify that optimizations (caching changes, image optimization, code splitting) are having the desired effect.

* * *

## Lighthouse Opportunities

Below the metrics, the Performance tab displays **Lighthouse optimization opportunities** - specific suggestions for improving performance, such as:

- Properly size images
- Eliminate render-blocking resources
- Reduce unused JavaScript
- Serve images in next-gen formats
- Enable text compression

Each opportunity includes an estimated time savings and a priority level.

* * *

## Performance Grading

Pages receive a performance grade based on the composite Lighthouse score:

| Score  | Grade |
|--------|-------|
| 90-100 | **A** |
| 80-89  | **B** |
| 70-79  | **C** |
| 60-69  | **D** |
| 0-59   | **F** |

* * *

## Domain Performance Summary

From the domain dashboard, you can see aggregate performance data across all pages that have been measured. This includes:

- Average performance score across measured pages
- Distribution of performance grades
- Pages with the worst performance scores for prioritized optimization

[**Pages & URL Detail**  
→  
\
Navigate to any page to access the Performance tab.](/docs/pages-overview)

[**Edge Cache**  
→  
\
Caching reduces TTFB and improves overall performance scores.](/docs/edge-cache)

[**Edge Crawler**  
→  
\
Crawl pages first to make them available for performance measurement.](/docs/edge-crawler)