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Frontend performance testing and analytics CLI tool for AI agents and developers.

Features

• Core Web Vitals - LCP, FID, CLS, INP, TTFB measurement
• FPS Monitoring - Real-time frame rate and jank detection
• Memory Profiling - Heap snapshot and memory leak detection
• JS Performance - CPU profiling and function execution analysis
• Lighthouse Integration - Comprehensive performance audits
• Trace Analysis - Chrome DevTools trace file analysis with problem detection
• AI-Ready Output - JSON format optimized for LLM analysis

Quick Start

# Install dependencies
npm install

# Build TypeScript
npm run build

# Run comprehensive check
node ./dist/cli/index.js check https://example.com

Usage

Comprehensive Check (Recommended)

node ./dist/cli/index.js check <url>

This runs all tests:

1. Core Web Vitals (LCP, CLS, TTFB, etc.)
2. FPS Monitoring (frame drops, jank)
3. Memory Analysis (leak detection)
4. JS Performance (CPU profiling)

Individual Tests

# Core Web Vitals only
node ./dist/cli/index.js cwv <url>

# Full performance test (CWV + Lighthouse)
node ./dist/cli/index.js perf <url>

# Capture trace for Chrome DevTools
node ./dist/cli/index.js trace <url>

# Analyze existing trace file
node ./dist/cli/index.js analyze <trace.json>

Output Directory

Default output directory: tests/

# Save results to tests/
node ./dist/cli/index.js check https://example.com -o tests/result.json

# Save trace to tests/
node ./dist/cli/index.js trace https://example.com -o tests/trace.json

# Save analysis report to tests/
node ./dist/cli/index.js analyze tests/trace.json -o tests/report.md

Options

| Option | Description | Default | | --------------- | -------------------------------------------------------------- | ------------ | | --network | Network throttling: slow-2g, 3g, fast-3g, 4g, offline | online | | --cpu | CPU throttling rate (1=normal, 4=4x slower) | 1 | | --viewport | Viewport size (e.g., 1920x1080) | 1920x1080 | | --mobile | Emulate mobile device (375x812) | false | | --no-headless | Run in visible browser window | headless | | -o, --output | Output file path | - | | --duration | Monitoring duration in seconds | 10 | | --wait-until | Wait event: load, domcontentloaded, networkidle0, networkidle2 | networkidle2 |

Examples

# Basic check
node ./dist/cli/index.js check https://example.com -o tests/result.json

# Slow network simulation
node ./dist/cli/index.js check https://example.com --network 3g -o tests/result.json

# Mobile device emulation
node ./dist/cli/index.js check https://example.com --mobile -o tests/result.json

# CPU throttling (4x slower)
node ./dist/cli/index.js check https://example.com --cpu 4 -o tests/result.json

# Capture trace for flame graph
node ./dist/cli/index.js trace https://example.com -o tests/trace.json

# Analyze trace and get LLM-friendly report
node ./dist/cli/index.js analyze tests/trace.json -o tests/report.md

Output Interpretation

Core Web Vitals

| Metric | Good | Needs Improvement | Poor | | ------ | ------- | ----------------- | -------- | | LCP | < 2.5s | 2.5s - 4s | > 4s | | CLS | < 0.1 | 0.1 - 0.25 | > 0.25 | | FID | < 100ms | 100ms - 300ms | > 300ms | | INP | < 200ms | 200ms - 500ms | > 500ms | | TTFB | < 800ms | 800ms - 1800ms | > 1800ms |

FPS

| Status | FPS | Dropped Frames | | -------------- | ----- | -------------- | | ✅ Good | 60 | 0 | | ⚠️ Mild Jank | 30-60 | 1-10 | | ❌ Severe Jank | <30 | >10 |

Memory

| Status | Growth | | -------- | ------ | | ✅ OK | <1MB | | ⚠️ Minor | 1-5MB | | ❌ Leak | >5MB |

Use Cases

For AI Agents

# Agent task: Analyze page performance
node ./dist/cli/index.js check https://example.com -o tests/result.json
# → Returns JSON with all metrics

# Agent task: Find rendering issues
node ./dist/cli/index.js trace https://example.com -o tests/trace.json
# → Use Chrome DevTools to load trace.json

# Agent task: Debug with LLM
node ./dist/cli/index.js analyze tests/trace.json -o tests/report.md
# → LLM-friendly markdown report

For CI/CD

# Exit code 0 = pass, 1 = fail
node ./dist/cli/index.js perf https://example.com -o tests/lighthouse.json

# Check Lighthouse score
jq '.metrics.lighthouse.performance' tests/lighthouse.json

Exit

Press Ctrl+C or Ctrl+Z to exit cleanly.

Troubleshooting

Chrome not found

Set CHROME_PATH environment variable:

export CHROME_PATH="/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"

Permission denied

chmod +x ./dist/cli/index.js

Network errors

Use --no-headless to see browser errors, or try --network online.

Requirements

• Node.js 18+
• Google Chrome / Chromium installed

Releases

| Version | Date | Description | | ----------------------------------------------------------------- | ---------- | ------------------------------------------------------------------------------------------------------------------ | | v1.0.0 | 2026-03-13 | 🎉 Initial release - Core Web Vitals, FPS monitoring, memory profiling, Lighthouse integration, and trace analysis |

License

MIT License - See LICENSE