Core Web Vitals optimized

Severity: Recommended

Core Web Vitals (FCP, LCP, CLS) directly impact SEO rankings and user experience. These metrics should be measured and optimized, especially for marketing/SEO-critical pages.

Check automatically:

1. Run PageSpeed Insights API (free, no auth required):

# Replace URL with actual production URL
curl -s "https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url=https://example.com&category=performance" | jq '{
  performance_score: (.lighthouseResult.categories.performance.score * 100),
  FCP: .lighthouseResult.audits["first-contentful-paint"].displayValue,
  LCP: .lighthouseResult.audits["largest-contentful-paint"].displayValue,
  CLS: .lighthouseResult.audits["cumulative-layout-shift"].displayValue,
  TBT: .lighthouseResult.audits["total-blocking-time"].displayValue
}'

2. Check for CLS culprits (images without dimensions, dynamic content):

curl -s "https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url=https://example.com&category=performance" | jq '.lighthouseResult.audits["layout-shift-elements"].details.items // empty'

3. Check for render-blocking resources:

curl -s "https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url=https://example.com&category=performance" | jq '.lighthouseResult.audits["render-blocking-resources"].details.items | length'

4. Test multiple key pages (not just homepage):

# Test landing page, product page, etc.
for url in "https://example.com" "https://example.com/pricing" "https://example.com/product"; do
  echo "Testing: $url"
  curl -s "https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url=$url&category=performance" | jq '{
    url: .lighthouseResult.finalUrl,
    score: (.lighthouseResult.categories.performance.score * 100),
    LCP: .lighthouseResult.audits["largest-contentful-paint"].displayValue
  }'
done

Ask user:

• "Which pages are SEO-critical or marketing landing pages?"
• If scores are low: "Is this a known issue being addressed?"

Pass criteria:

• Performance score ≥ 90 (good), ≥ 50 (acceptable)
• FCP < 1.8s (good), < 3s (acceptable)
• LCP < 2.5s (good), < 4s (acceptable)
• CLS < 0.1 (good), < 0.25 (acceptable)

Fail criteria:

• Performance score < 50
• LCP > 4s
• CLS > 0.25 (significant layout shifts)
• FCP > 3s

Cross-reference with:

• FEP-001 (automated reports should catch regressions)
• FEP-003 (font preloading improves FCP/LCP)
• FEP-004 (CSS preloading improves FCP)
• CACHE-001/002 (caching improves repeat visits)

Evidence to capture:

• Performance score
• All Core Web Vitals values (FCP, LCP, CLS, TBT)
• URLs tested
• Any flagged layout shift elements
• Number of render-blocking resources

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