Understanding results

A guide to the Lighthouse Result (LHR) object structure, score interpretation, and report formats.

Every Lighthouse run produces a Lighthouse Result object (LHR). The LHR is the source of truth behind the HTML report — everything you see rendered in the report is derived from it. You interact with it directly when using Lighthouse programmatically, consuming CLI JSON output, or building tooling on top of Lighthouse.

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The RunnerResult object

When you call lighthouse() from Node, the return value wraps the LHR:

import lighthouse from 'lighthouse';
import * as chromeLauncher from 'chrome-launcher';

const chrome = await chromeLauncher.launch({chromeFlags: ['--headless']});
const runnerResult = await lighthouse('https://example.com', {port: chrome.port});

// The full LHR as a JS object
const lhr = runnerResult.lhr;

// The formatted report string (HTML by default)
const report = runnerResult.report;

// Check a specific score
console.log('Performance score:', lhr.categories.performance.score * 100);

await chrome.kill();

lhr · LH.Result · required

The Lighthouse Result object. Contains all audit results, scores, and metadata.

report · string | string[] · required

The formatted report. A string for single-format runs; an array when multiple --output formats are requested.

artifacts · object · required

Raw gathered artifacts from the page (traces, network logs, DOM snapshots, etc.).

---

Top-level LHR fields

lighthouseVersion · string · required

The version of Lighthouse that generated this result (e.g. "12.0.0").

fetchTime · string · required

ISO-8601 timestamp of when the result was generated (e.g. "2024-01-15T10:30:00.000Z").

requestedUrl · string · required

The URL that was originally passed to Lighthouse.

mainDocumentUrl · string · required

The URL of the main document request during the final navigation.

finalDisplayedUrl · string · required

The URL shown in the browser after all redirects and history API changes. Use this as the canonical URL for the run.

userAgent · string · required

The Chrome user agent string used during the audit.

categories · object · required

Category scores and audit references. See Categories.

audits · object · required

Individual audit results keyed by audit ID. See Audits.

configSettings · object · required

The resolved configuration settings used for this run. See configSettings.

timing · object · required

Timing information for the run. See Timing.

categoryGroups · object

Display groups used to visually cluster audits within a category in the HTML report.

runtimeError · object

Present when a fatal error prevented a valid result. Contains code and message fields. If set, treat the result as unreliable.

runWarnings · string[]

Top-level warnings about the run (e.g. throttling was overridden).

Example

{
  "lighthouseVersion": "12.0.0",
  "fetchTime": "2024-01-15T10:30:00.000Z",
  "requestedUrl": "https://example.com",
  "mainDocumentUrl": "https://www.example.com/",
  "finalDisplayedUrl": "https://www.example.com/",
  "categories": {},
  "audits": {},
  "configSettings": {},
  "timing": {}
}

---

Categories

The lhr.categories object contains one entry per scored category. Each key is the category ID (e.g. "performance").

id · string · required

The category identifier, e.g. performance, accessibility, best-practices, seo.

title · string · required

The human-readable category name shown in the report.

description · string · required

A brief description of what the category measures.

score · number | null · required

The weighted average of all audit scores in the category, in the range 0–1. May be null for non-scored categories.

auditRefs · object[] · required

References to the audits that contribute to this category.

Show auditRef properties

id · string

The audit ID.

weight · number

The audit’s weight in the category score.

group · string

Optional display group ID.

Example

{
  "performance": {
    "id": "performance",
    "title": "Performance",
    "description": "These encapsulate your web app's performance...",
    "score": 0.87,
    "auditRefs": [
      {"id": "first-contentful-paint", "weight": 10, "group": "metrics"},
      {"id": "interactive", "weight": 10, "group": "metrics"}
    ]
  },
  "seo": {
    "id": "seo",
    "title": "SEO",
    "description": "These checks ensure your page is following basic SEO advice...",
    "score": 0.54,
    "auditRefs": [{"id": "crawlable-anchors", "weight": 1}]
  }
}

---

Audits

The lhr.audits object contains every audit result, keyed by the audit ID.

id · string · required

The audit identifier in kebab-case (e.g. "first-contentful-paint").

title · string · required

The display name of the audit. May change between pass and fail states. Supports Markdown code spans.

description · string · required

Explains why the audit matters, with links to Lighthouse documentation. Supports Markdown links.

score · number | null · required

A value in the range 0–1, or null when scoreDisplayMode is informative, manual, notApplicable, or error.

scoreDisplayMode · string · required

Controls how the score is rendered. See Score display modes.

displayValue · string

Human-readable summary shown alongside the audit result (e.g. "2.4 s", "5 resources found").

numericValue · number

The raw numeric value for the audit (e.g. milliseconds for timing metrics).

explanation · string

A string explaining why the audit failed.

warnings · string[]

Messages about potentially invalid or edge-case conditions.

details · object

Structured data used to render the audit’s details table in the report. Structure varies by audit type.

Example

{
  "is-on-https": {
    "id": "is-on-https",
    "title": "Does not use HTTPS",
    "description": "All sites should be protected with HTTPS... [Learn more](https://...)",
    "score": 0,
    "scoreDisplayMode": "binary",
    "displayValue": "1 insecure request found",
    "details": {
      "type": "table",
      "headings": [{"key": "url", "valueType": "url", "label": "Insecure URL"}],
      "items": [{"url": "http://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"}]
    }
  }
}

---

Score interpretation

Audit and category scores are values between 0 and 1. The report renders them as 0–100.

Range	Value	Color	Meaning
0.9 – 1.0	90–100	Green	Pass
0.5 – 0.89	50–89	Orange	Needs improvement
0.0 – 0.49	0–49	Red	Fail

// Convert a score to the 0-100 display value
const score = lhr.categories.performance.score * 100;

if (score >= 90) console.log('Pass');
else if (score >= 50) console.log('Needs improvement');
else console.log('Fail');

Performance scores are highly sensitive to environment. Always run multiple times and average the results before drawing conclusions.

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Score display modes

The scoreDisplayMode field on each audit determines how it is presented.

Mode	Score value	Description
numeric	0–1	Scored on a continuous scale. Used by most performance metrics.
binary	0 or 1	Pass/fail. Score is exactly 0 or 1.
informative	null	Not scored. Informational only, shown as a neutral item.
manual	null	Requires human review. Not automatically assessed.
notApplicable	null	The audit does not apply to this page. Hidden from the report.
error	null	The audit encountered an error and could not run.

---

configSettings

Reflects the configuration that was actually used for the run, after merging flags and config.

{
  "output": ["json"],
  "maxWaitForLoad": 45000,
  "throttlingMethod": "devtools",
  "throttling": {
    "rttMs": 150,
    "throughputKbps": 1638.4,
    "requestLatencyMs": 562.5,
    "downloadThroughputKbps": 1474.56,
    "uploadThroughputKbps": 675,
    "cpuSlowdownMultiplier": 4
  },
  "gatherMode": false,
  "disableStorageReset": false,
  "formFactor": "mobile",
  "blockedUrlPatterns": null,
  "onlyAudits": null,
  "onlyCategories": null,
  "skipAudits": null
}

---

timing

Contains performance information about the Lighthouse run itself.

Field	Type	Description
total	number	Total time in milliseconds Lighthouse spent loading the page and running all audits.

{
  "total": 32189
}

---

Report formats

Lighthouse can produce three report formats from the same LHR.

Format	Flag	Description
HTML	--output html	Self-contained HTML file with all styles and screenshots embedded. The default output.
JSON	--output json	The full LHR serialized as JSON. Suitable for programmatic processing and CI integration.
CSV	--output csv	A flat CSV file with one row per audit. Does not include flow results.

Accessing reports programmatically

import lighthouse, {generateReport} from 'lighthouse';

const runnerResult = await lighthouse('https://example.com', {port: chrome.port});

// The LHR (structured data)
const lhr = runnerResult.lhr;
console.log('Performance:', lhr.categories.performance.score * 100);

// Generate specific formats from the same LHR
const htmlReport = generateReport(lhr, 'html');
const jsonReport = generateReport(lhr, 'json');
const csvReport  = generateReport(lhr, 'csv');

For CI use cases, consume the JSON output programmatically rather than parsing the HTML report. The LHR schema is versioned and more stable.

Viewing JSON output online

Run Lighthouse with --output=json and drag the file onto the Lighthouse Viewer to render the full HTML report in a browser without saving an HTML file locally. Reports shared from the viewer are stored as secret GitHub Gists under your account.