7.3Lighthouse CI Configuration

The core configuration lives in a lighthouserc.json file at the root of your project:

{
  "ci": {
    "collect": {
      "url": [
        "https://staging.example.com/",
        "https://staging.example.com/products/1",
        "https://staging.example.com/checkout"
      ],
      "numberOfRuns": 3,
      "settings": {
        "chromeFlags": "--no-sandbox --headless",
        "throttling": {
          "cpuSlowdownMultiplier": 4,
          "downloadThroughputKbps": 1600,
          "uploadThroughputKbps": 768,
          "rttMs": 150
        }
      }
    },
    "assert": {
      "assertions": {
        "categories:performance": ["error", { "minScore": 0.9 }],
        "categories:accessibility": ["error", { "minScore": 0.95 }],
        "first-contentful-paint": ["error", { "maxNumericValue": 1800 }],
        "largest-contentful-paint": ["error", { "maxNumericValue": 2500 }],
        "cumulative-layout-shift": ["error", { "maxNumericValue": 0.1 }],
        "interactive": ["error", { "maxNumericValue": 3800 }],
        "total-blocking-time": ["warn", { "maxNumericValue": 300 }],
        "speed-index": ["warn", { "maxNumericValue": 3400 }]
      }
    },
    "upload": {
      "target": "lhci",
      "serverBaseUrl": "https://lhci.internal.example.com"
    }
  }
}

Configuration Breakdown

collect: Defines what to measure.

• url: List of pages to audit. Always include your most critical user journeys.
• numberOfRuns: Run each URL multiple times. Lighthouse CI reports the median, which reduces variance from network jitter.
• settings.throttling: Simulate realistic network conditions. The default simulates a mid-tier mobile device on a 4G connection.

assert: Defines what must pass.

• "error" level assertions fail the pipeline.
• "warn" level assertions produce warnings but do not block deployment.
• Assertions can target category scores (0-1 scale) or specific metrics (milliseconds).

upload: Optional -- stores results for historical comparison.