performance-audit

name	performance-audit
description	Analyze web and backend performance using Web Vitals, network timing, and Node.js metrics. Use when the user asks about page performance, load times, Core Web Vitals (LCP, CLS, INP), slow pages, backend bottlenecks, or SEO performance factors.
allowed-tools	Bash(browser-devtools-cli:*), Bash(node-devtools-cli:*)

Performance Audit Skill

Analyze web page performance using Web Vitals and network timing metrics.

When to Use

This skill activates when:

• User asks about page performance or speed
• User wants to optimize load times
• User mentions slow page, slow API, or poor user experience
• User needs Core Web Vitals metrics
• User asks about backend bottlenecks or TTFB
• User asks about SEO performance factors

Capabilities

Web Vitals Analysis

browser-devtools-cli o11y get-web-vitals
browser-devtools-cli --json o11y get-web-vitals
browser-devtools-cli --json o11y get-web-vitals --wait-ms 3000
browser-devtools-cli --json o11y get-web-vitals --include-debug

Network Performance

browser-devtools-cli --json o11y get-http-requests
browser-devtools-cli --json o11y get-http-requests --resource-type script
browser-devtools-cli --json o11y get-http-requests --resource-type stylesheet
browser-devtools-cli --json o11y get-http-requests --status '{"min":400}'

Visual Analysis

browser-devtools-cli content take-screenshot --name "above-fold"
browser-devtools-cli content take-screenshot --name "full-page" --full-page

Performance Thresholds

Metric	Good	Needs Work	Poor
LCP	≤2.5s	2.5-4s	>4s
INP	≤200ms	200-500ms	>500ms
CLS	≤0.1	0.1-0.25	>0.25
TTFB	≤800ms	800-1800ms	>1800ms
FCP	≤1.8s	1.8-3s	>3s

Audit Workflow

SESSION="--session-id perf-audit"

# 1. Navigate to page
browser-devtools-cli $SESSION navigation go-to --url "https://example.com"

# 2. Wait for page to settle
browser-devtools-cli $SESSION sync wait-for-network-idle

# 3. Get Web Vitals
browser-devtools-cli $SESSION --json o11y get-web-vitals --wait-ms 2000

# 4. Analyze network requests
browser-devtools-cli $SESSION --json o11y get-http-requests

# 5. Check for console errors
browser-devtools-cli $SESSION --json o11y get-console-messages --type warning

# 6. Take screenshot for reference
browser-devtools-cli $SESSION content take-screenshot --name "performance-audit"

# 7. Cleanup
browser-devtools-cli session delete perf-audit

Detailed Analysis

Check Large Resources

# Filter by type (one at a time: document, stylesheet, image, script, xhr, fetch, etc.)
browser-devtools-cli --json o11y get-http-requests --resource-type script
browser-devtools-cli --json o11y get-http-requests --resource-type stylesheet
browser-devtools-cli --json o11y get-http-requests --resource-type image

Check Slow Requests

browser-devtools-cli --json o11y get-http-requests
# Look for requests with high timing values

Backend Performance (node-devtools-cli)

When TTFB or API latency suggests backend bottlenecks, inspect the Node.js process:

# Connect to API/server process
node-devtools-cli --session-id perf debug connect --pid 12345

# Tracepoint on slow handler to capture call context
node-devtools-cli --session-id perf debug put-tracepoint \
  --url-pattern "routes/heavy.ts" \
  --line-number 30

Common Issues

• Large unoptimized images
• Render-blocking CSS/JS
• Too many HTTP requests
• Slow server response (TTFB)
• Layout shifts from dynamic content
• Uncompressed resources
• Missing caching headers
• Third-party scripts blocking main thread

Best Practices

1. Run multiple times for consistent results
2. Wait for network idle before measuring
3. Use --wait-ms for LCP/CLS to settle
4. Check network requests for slow/large resources
5. Take screenshots at different load stages
6. Test on different network conditions (throttle if needed)
7. Compare before/after for optimization validation