{
  "slug": "lighthouse-category-scores",
  "name": "Lighthouse category scores",
  "aliases": [
    "Non-CWV Lighthouse scores",
    "SEO and accessibility scores"
  ],
  "definition": "The eight further Lighthouse figures collected alongside the Core Web Vitals: SEO, accessibility, best practices, Time to Interactive, Total Blocking Time, First Contentful Paint, Speed Index, and the mobile score.",
  "category": "Page experience",
  "type": "score",
  "unit": "two scales: SEO, accessibility, best practices and the mobile score are 0-to-1 score fractions; Time to Interactive, Total Blocking Time, First Contentful Paint and Speed Index are seconds",
  "direction": "neutral",
  "verification": "verified",
  "calculation": "Each figure is read straight from its own summary measure over the pages in scope, with no derivation on top. The four score-type figures arrive as fractions between nought and one and carry an explicit display contract: multiply by a hundred and round to a whole score point, presented without a percent sign, so 0.925 is shown as 93. The four timing figures arrive in seconds. None of the eight is graded.",
  "aggregation": "Seven of the eight are plain averages of their per-row values across the pages in scope. The mobile score is the exception: it is impression-weighted in the semantic layer, dividing the sum of score times impressions by the sum of impressions.",
  "grain": "One number per figure per date range.",
  "dimensions": [
    "device"
  ],
  "requiredFilters": [
    "date_range"
  ],
  "sources": [
    "lighthouse"
  ],
  "reports": [
    "core-web-vitals-report"
  ],
  "skills": [
    "technical-health-audit"
  ],
  "verbs": [
    "site_health_cwv_check"
  ],
  "rungs": [
    "R1"
  ],
  "levers": [
    "L1"
  ],
  "questions": [
    "What is our accessibility score?",
    "How does our SEO audit score look?"
  ],
  "interpretation": "The wider audit that sits beside page experience without being part of it. None of the eight is graded and none feeds the page-experience verdict, so they are context for a conversation rather than inputs to one, and because the set spans two scales, a figure quoted without naming which of the eight it is cannot be read at all.",
  "caveats": [
    "Returned as raw averages and deliberately NOT graded. There is no good, needs-improvement or poor band for any of the eight; assigning one invents a threshold the product does not have.",
    "Two scales in one set. Four are score fractions between nought and one, four are seconds, they are never comparable to each other as numbers.",
    "The score-type figures must be shown as whole score points, not as percentages: the raw fraction is multiplied by a hundred and rounded, with no percent sign. Rendering 0.93 as 0.93% or as 93% are both wrong.",
    "Opt-in: they are only fetched when explicitly requested, and are absent from a default page-experience read.",
    "The mobile score is aggregated differently from the other seven, impression-weighted rather than a plain average, so the set is internally inconsistent in how it rolls up.",
    "First Contentful Paint's direction is still contested between the two shared oracles: one reads a rise as a regression, the other as an improvement. Do not paint a movement in it green or red.",
    "These are lab measurements, not field data from real visitors; collection cadence varies by site and by page."
  ],
  "freshness": "varies by site, priority URLs can run nightly; most pages far less often. The collection date rides on the card rather than being assumed.",
  "failureModes": [
    "Grading these against Core Web Vitals bands, or presenting one as good or poor.",
    "Rendering a score fraction as a decimal percentage instead of a whole score point.",
    "Comparing the mobile score against the other seven as if aggregated the same way, or comparing a score against a timing figure.",
    "Treating a movement in one of these as a Core Web Vitals regression."
  ],
  "notSameAs": [
    {
      "slug": "performance-score",
      "why": "The performance score is graded and drives the overall verdict; these eight are ungraded and drive nothing. The performance score also shares the 0-to-1 scale of four of them, which is exactly why the two are confused."
    },
    {
      "slug": "cwv-vital-grade",
      "why": "There is no grade for any of these eight. Presenting one as good or poor invents a band the product does not have."
    }
  ],
  "related": [
    "performance-score",
    "largest-contentful-paint"
  ],
  "workflows": [],
  "lastVerified": "2026-08-04"
}