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Lighthouse Report Viewer

Open a Lighthouse or PageSpeed JSON report and see what to fix first.

Private by design

Your inputs stay on your device and are not sent to our servers. Optional usage analytics does not receive your files or tool inputs.

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How to use Lighthouse Report Viewer

Open a Lighthouse or PageSpeed JSON file, or paste it, or start from the sample.
To compare, paste a second report into the Options panel.
Read the scores, metrics and fixes, then copy or download the summary.

Read the detailed guide →

What are the limits of Lighthouse Report Viewer?

Reads reports you already have; it does not run Lighthouse or fetch any page. Fix order uses the time and bytes each audit says it can save, so treat it as a guide. Your data stays on your device.

Lighthouse Report Viewer

Scores, Core Web Vitals and fixes by impact

Lighthouse or PageSpeed JSON (report A)

{
  "lighthouseVersion": "12.2.0",
  "fetchTime": "2026-01-02T03:04:05.000Z",
  "finalDisplayedUrl": "https://example.com/",
  "configSettings": {
    "formFactor": "mobile"
  },
  "categories": {
    "performance": {
      "title": "Performance",
      "score": 0.62,
      "auditRefs": [
        {
          "id": "first-contentful-paint",
          "weight": 10
        },
        {
          "id": "largest-contentful-paint",
          "weight": 25
        },
        {
          "id": "total-blocking-time",
          "weight": 30
        },
        {
          "id": "cumulative-layout-shift",
          "weight": 25
        },
        {
          "id": "uses-optimized-images",
          "weight": 0
        },
        {
          "id": "unused-javascript",
          "weight": 0
        }
      ]
    },
    "accessibility": {
      "title": "Accessibility",
      "score": 0.94,
      "auditRefs": []
    }
  },
  "audits": {
    "first-contentful-paint": {
      "title": "First Contentful Paint",
      "score": 0.7,
      "scoreDisplayMode": "numeric",
      "numericValue": 2100
    },
    "largest-contentful-paint": {
      "title": "Largest Contentful Paint",
      "score": 0.4,
      "scoreDisplayMode": "numeric",
      "numericValue": 4500
    },
    "total-blocking-time": {
      "title": "Total Blocking Time",
      "score": 0.7,
      "scoreDisplayMode": "numeric",
      "numericValue": 350
    },
    "cumulative-layout-shift": {
      "title": "Cumulative Layout Shift",
      "score": 1,
      "scoreDisplayMode": "numeric",
      "numericValue": 0.05
    },
    "uses-optimized-images": {
      "title": "Efficiently encode images",
      "score": 0.2,
      "scoreDisplayMode": "numeric",
      "displayValue": "Potential savings of 200 KiB",
      "details": {
        "type": "opportunity",
        "overallSavingsMs": 900,
        "overallSavingsBytes": 204800
      }
    },
    "unused-javascript": {
      "title": "Reduce unused JavaScript",
      "score": 0.5,
      "scoreDisplayMode": "numeric",
      "details": {
        "type": "opportunity",
        "overallSavingsMs": 300,
        "overallSavingsBytes": 90000
      }
    }
  }
}

Summary

The result appears here.

Options

Report B (optional, to compare)

Fixes to list

Lighthouse is the free audit built into Chrome DevTools; PageSpeed Insights runs it for you online. Both can give you a JSON file. Paste or open it here to read scores, Core Web Vitals and the fixes that save the most time, with no upload.

In Chrome DevTools, open Lighthouse, run an audit, then use the three-dot menu and Save as JSON.
For PageSpeed Insights, copy the JSON from its API response; the lab data inside lighthouseResult is read.
Compare two runs of the same page and the same device type; runs vary a little each time.

Reads the lighthouseResult (or top-level) categories and audits. Metric ratings use the published Core Web Vitals and Lighthouse thresholds (LCP 2.5 s / 4 s, CLS 0.1 / 0.25, TBT 200 / 600 ms). Fixes rank by estimated time saved, then by weight times lost score. Field (real-user) data is not used.