vital-scans open quality ledger

www.cdc.gov: Lighthouse — week 2026-W40

166 pages sampled by Google Lighthouse (its own headless Chrome). Scores are 0–100 (higher is better); metrics are Core Web Vitals. Download: CSV (per-page scores) · JSON (AI-ready, includes recommendations) · Priority pages CSV · Priority pages JSON.

Trend

Lighthouse category scores over 17 weeks
Performance Accessibility Best practices SEO W24W32W401000
Lighthouse category scores by week
WeekPerformanceAccessibilityBest practicesSEO
2026-W2482100100100
2026-W257710096100
2026-W267810096100
2026-W2780100100100
2026-W288210096100
2026-W298210096100
2026-W308410096100
2026-W318210096100
2026-W328210096100
2026-W337710096100
2026-W347910096100
2026-W358310096100
2026-W368610096100
2026-W378010096100
2026-W388310096100
2026-W398099100100
2026-W4082100100100

History & Trends → Severity, Lighthouse and other measures across 17 weeks.

Performance impact

How far pages fall short of Google's "good" benchmarks: Largest Contentful Paint ≤ 2.5s and page weight ≤ 1.6 MB. Lower is better.

Avg extra LCP over 2.5s
3.5s 105/165 pages over
Avg extra weight over 1.6 MB
3.94 MB 142/193 pages over

Set page_loads_per_week for this target to also estimate total wasted time and data (the way daily-dap uses traffic counts).

Medians across sampled pages

Performance
82/100
Accessibility
100/100
Best practices
100/100
SEO
100/100
Agentic browsing
94/100
Largest Contentful Paint
3.0s
First Contentful Paint
1.6s
Speed Index
4.3s
Total Blocking Time
0.2s
Cumulative Layout Shift
0.018

Recommendations

Issues Lighthouse flagged across the 166 sampled page(s), beyond the headline scores — grouped by category and ranked by how many pages they affect. Estimated savings (transfer bytes or load time) are Lighthouse's own estimates where available. Accessibility audits are intentionally omitted; they overlap with the axe-core findings on the Accessibility page.

Performance

Performance recommendations from Lighthouse, by sampled pages affected.
RecommendationPagesEst. saving
Reduce unused JavaScript 164/166 24.9 MB · 28.9s
JavaScript execution time 163/166 42.8s
Minimize main-thread work 159/166 37.1s
Network dependency tree 158/166 —
Use efficient cache lifetimes 148/166 418.6s
Time to Interactive 140/166 —
Render-blocking requests 126/166 77.8s
Reduce unused CSS 125/166 9.8 MB · 54.5s
Minify JavaScript 107/166 4.4 MB · 10.9s
Largest Contentful Paint 105/166 —
Font display 99/166 5.5s
Speed Index 99/166 —
Avoid multiple page redirects 90/166 70.8s
Improve image delivery 61/166 120.7s
Total Blocking Time 56/166 —
LCP request discovery 52/166 —
Max Potential First Input Delay 51/166 —
Layout shift culprits 50/166 —
First Contentful Paint 49/166 —
Forced reflow 26/166 —
Document request latency 16/166 1.4s
Legacy JavaScript 13/166 1.9s
Page prevented back/forward cache restoration 8/166 —
Initial server response time was short 4/166 0.3s
Minify CSS 2/166 30 KB

Best Practices

Best Practices recommendations from Lighthouse, by sampled pages affected.
RecommendationPagesEst. saving
Browser errors were logged to the console 50/166 —
Serves images with low resolution 44/166 —
Page lacks the HTML doctype, thus triggering quirks-mode 40/166 —
Issues were logged in the `Issues` panel in Chrome Devtools 37/166 —
Does not use HTTPS 32/166 —
Displays images with incorrect aspect ratio 22/166 —
Charset declaration is missing or occurs too late in the HTML 19/166 —
Missing source maps for large first-party JavaScript 3/166 —

SEO

SEO recommendations from Lighthouse, by sampled pages affected.
RecommendationPagesEst. saving
Document does not have a meta description 53/166 —
Image elements do not have `[alt]` attributes 32/166 —
Links do not have descriptive text 15/166 —
Links are not crawlable 2/166 —

Agentic (AI-readiness)

Agentic (AI-readiness) recommendations from Lighthouse, by sampled pages affected.
RecommendationPagesEst. saving
WebMCP tools registered 165/166 —
WebMCP form coverage 165/166 —
WebMCP schemas are valid 165/166 —
llms.txt follows recommendations 165/166 —
Cumulative Layout Shift 52/166 —
Accessibility tree is not well-formed 39/166 —

What the Agentic score means

The Agentic (AI-readiness) score is new in Google Lighthouse (13.4+). It measures how well a page works for AI agents and assistants — the tools that increasingly mediate how people find and use government services. It checks for things like an llms.txt file (a machine-readable guide for language models), valid structured data, a well-formed accessibility tree that agents can parse, and WebMCP tool/form descriptions. A higher score means an AI assistant is more likely to understand the page and complete tasks on a citizen's behalf correctly.

It is experimental and evolving; treat it as a forward-looking signal, not a compliance requirement. Median across sampled pages: 94/100.

Gaps found on the sampled pages: WebMCP tools registered (165), WebMCP form coverage (165), WebMCP schemas are valid (165), llms.txt follows recommendations (165), Cumulative Layout Shift (52), Accessibility tree is not well-formed (39).

Per-page results

Lighthouse scores and Core Web Vitals per sampled page (2026-W40). Agentic = experimental agentic-browsing score. PWA / offline readiness is tracked in the Standards tab (Lighthouse 12+ removed the PWA category). — click a column heading to sort
/acute-bronchitis/about/index.html901001001001001.2s3.0s4.3s0.2s0.003
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/national-asthma-control-program/site.html951001001001001.2s2.0s3.8s0.2s0.013
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/diabetes/living-with/mental-health.html76100100100961.6s4.4s4.8s0.2s0.089
/lead-prevention/php/data/nhanes.html891001001001001.6s2.9s4.9s0.2s0.003
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/howrightnow/gratitude/index.html4610096100542.1s33.1s2.4s0.2s0.653
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/diabetes/signs-symptoms/index.html77100100100851.6s3.7s5.1s0.1s0.174
/polaris/php/economics/cost-analysis.html78100100100841.2s3.6s4.1s0.2s0.175
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/mmwr/volumes/71/wr/mm7138e2.htm619896100712.3s4.1s2.3s0.4s0.287
/brfss/acbs/2017/multiple_year/acbs_prevalence_15-17_table2a.html399610092542.7s6.6s5.7s0.3s0.658
/cannabis/health-effects/cannabis-use-disorder.html951001001001001.2s1.4s5.0s0.1s0.046
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/mmwr/volumes/70/wr/mm7040e3.htm3398961001006.7s34.3s10.6s1.1s0
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/nchs/injury/injury_links.htm681009692682.3s3.1s2.3s0.3s0.328
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/mmwr/preview/mmwrhtml/mm6013a2.htm98798592501.4s2.2s1.4s0.1s0
/covid/vaccines88100100100961.2s2.9s4.9s0.1s0.094
/leishmaniasis/about/index.html86100100100931.2s3.0s4.8s0.1s0.117
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/hepatitis-b/about/index.html679110085502.2s12.4s6.5s0.1s0.009
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/dengue/stories/integrated-mosquito-control.html68100100100941.2s6.5s5.7s0.1s0.109
/pinkbook/hcp/table-of-contents881001001001001.7s2.7s5.0s0.2s0.002
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/group-a-strep/about/strep-throat.html659110085502.2s15.0s7.2s0.1s0.009
/pulsenet/about/index.html80100100100981.6s3.4s5.1s0.3s0.075
/diabetes/caring/5-questions-health-care-team.html79100100100931.6s3.5s5.7s0.2s0.114
/adenovirus/about/index.html87100100100941.2s3.2s4.0s0.1s0.111
/mmwr/preview/mmwrhtml/mm5644a1.htm1006267831001.2s1.3s1.2s0.1s0
/niosh/bulletin/2023/cannabis-allergies.html921001001001001.6s2.0s5.0s0.2s0.035
/mmwr/volumes/65/wr/mm6519a2.htm69959692712.0s3.6s2.1s0.2s0.287
/importation/index.html75100100921001.6s5.7s4.6s0.1s0.002
/mmwr/preview/mmwrhtml/00000353.htm1006262831000.8s1.0s0.8s0.0s0
/niosh/docs/2016-106/default.html921001001001001.7s2.2s4.8s0.2s0.037
/nchs/products/databriefs/db399.htm4510096100582.7s7.4s2.7s0.3s0.497
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/mmwr/volumes/70/wr/mm7033a2.htm699896100762.0s4.0s2.0s0.3s0.239
/readiness/php/testgame/test-pod-discussion-guide.html711001001001001.2s2.7s5.9s0.9s0.012
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/monkeypox/hcp/clinical-care/pregnancy.html911001001001001.7s2.5s4.8s0.2s0.012
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/vaccines-for-children/about/index.html79100100100961.6s4.3s4.6s0.1s0.092
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/niosh/docs/mining/works/coversheet1118.html68100100100501.2s10.8s6.3s0.1s0.042
/botulism/diagnosing-treating/index.html83100100100941.5s3.3s4.2s0.2s0.106
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