Kruk - Chrome UX Report (CrUX) CLI Tool

Kruk is a command-line interface tool that helps you fetch and visualize Chrome User Experience Report (CrUX) data for websites. It provides easy access to real-world performance metrics collected from Chrome users.

Installation

npm install -g kruk

Usage

Basic syntax:

kruk --key YOUR_API_KEY --urls URL1,URL2 [options]

Required Parameters

• --key: Your Google API key (Get it from Google Cloud Console)
• --urls: Comma-separated list of URLs to analyze

Optional Parameters

• --formFactor: Device type to filter results (default: 'PHONE')
  • Options: 'ALL_FORM_FACTORS', 'DESKTOP', 'TABLET', 'PHONE'
• --ect: Effective Connection Type
  • Options: 'offline', 'slow-2G', '2G', '3G', '4G'
• --checkOrigin: Get data for the entire origin instead of specific URLs
• --history: Use CrUX history API to get historical data
• --output: Output format (default: 'table')
  • Options: 'distribution', 'json', 'csv', 'table'

Examples

1. Basic usage with multiple URLs:

kruk --key YOUR_API_KEY --urls www.google.com,www.bing.com

2. Check specific connection type:

kruk --key YOUR_API_KEY --urls www.google.com,www.bing.com --ect 4G

3. Check desktop metrics:

kruk --key YOUR_API_KEY --urls www.google.com,www.bing.com --formFactor DESKTOP

4. Get origin-level data:

kruk --key YOUR_API_KEY --urls www.google.com --checkOrigin

5. Get data for tablet users on 3G:

kruk --key YOUR_API_KEY --urls www.google.com,www.bing.com --formFactor TABLET --ect 3G

Output Metrics

The tool provides data for the following Core Web Vitals and additional metrics:

• CLS (Cumulative Layout Shift)
• FCP (First Contentful Paint)
• LCP (Largest Contentful Paint)
• TTFB (Time to First Byte)
• INP (Interaction to Next Paint)

Output Formats

1. Table (default): Displays data in a formatted table
2. Distribution: Shows visual distribution of metrics using unicode characters
3. CSV: Outputs data in CSV format for further processing
4. JSON: Raw JSON output of the data

Programmatic Usage

Kruk can also be used as a module in your Node.js applications.

Installation

npm install kruk

Basic Usage

import { getReports } from 'kruk';

async function fetchCruxData() {
  const urls = ['www.google.com', 'www.bing.com'];
  const API_KEY = 'YOUR_API_KEY';

  const params = {
    effectiveConnectionType: '4G', // optional
    formFactor: 'PHONE',          // optional
    origin: false,                // optional, set true for origin-level data
    history: false                // optional, set true for historical data
  };

  try {
    const data = await getReports(urls, API_KEY, params);
    console.log(data);
  } catch (error) {
    console.error(error);
  }
}

Response Structure

The response will include metrics data in the following format:

{
  params: {
    // Query parameters used
  },
  metrics: [
    {
      url: "https://www.example.com",
      CLS: {
        p75: number,
        rank: "good" | "average" | "poor",
        histogram: [number, number, number] // Distribution values
      },
      FCP: {
        // Similar structure as CLS
      },
      LCP: {
        // Similar structure as CLS
      },
      TTFB: {
        // Similar structure as CLS
      },
      INP: {
        // Similar structure as CLS
      }
    }
  ]
}

Requirements

• Node.js
• Google API Key with access to Chrome UX Report API

Note

The tool requires a valid Google API key with access to the Chrome UX Report API. Make sure to handle the API key securely and not share it in public repositories.