Chrome Devtools

Chrome DevTools Agent Skill

Browser automation via executable Puppeteer scripts. All scripts output JSON for easy parsing.

Quick Start

CRITICAL: Always check pwd before running scripts.

Installation

Step 1: Install System Dependencies (Linux/WSL only)

On Linux/WSL, Chrome requires system libraries. Install them first:

pwd  # Should show current working directory
cd .claude/skills/chrome-devtools/scripts
./install-deps.sh  # Auto-detects OS and installs required libs

Supports: Ubuntu, Debian, Fedora, RHEL, CentOS, Arch, Manjaro

macOS/Windows: Skip this step (dependencies bundled with Chrome)

Step 2: Install Node Dependencies

# Preferred: Using bun (faster)
bun install  # Installs puppeteer, debug, yargs

# Alternative: Using npm
npm install

Step 3: Install ImageMagick (Optional, Recommended)

ImageMagick enables automatic screenshot compression to keep files under 5MB:

macOS:

brew install imagemagick

Ubuntu/Debian/WSL:

sudo apt-get install imagemagick

Verify:

magick -version  # or: convert -version

Without ImageMagick, screenshots >5MB will not be compressed (may fail to load in Gemini/Claude).

Test

bun navigate.js --url https://example.com
# Output: {"success": true, "url": "https://example.com", "title": "Example Domain"}

Available Scripts

All scripts are in .claude/skills/chrome-devtools/scripts/

CRITICAL: Always check pwd before running scripts.

Script Usage

• ./scripts/README.md

Core Automation

• navigate.js - Navigate to URLs
• screenshot.js - Capture screenshots (full page or element)
• click.js - Click elements
• fill.js - Fill form fields
• evaluate.js - Execute JavaScript in page context

Analysis & Monitoring

• snapshot.js - Extract interactive elements with metadata
• console.js - Monitor console messages/errors
• network.js - Track HTTP requests/responses
• performance.js - Measure Core Web Vitals + record traces

Usage Patterns

Single Command

pwd  # Should show current working directory
cd .claude/skills/chrome-devtools/scripts
bun screenshot.js --url https://example.com --output ./docs/screenshots/page.png

Important: Always save screenshots to ./docs/screenshots directory.

Automatic Image Compression

Screenshots are automatically compressed if they exceed 5MB to ensure compatibility with Gemini API and Claude Code (which have 5MB limits). This uses ImageMagick internally:

# Default: auto-compress if >5MB
bun screenshot.js --url https://example.com --output page.png

# Custom size threshold (e.g., 3MB)
bun screenshot.js --url https://example.com --output page.png --max-size 3

# Disable compression
bun screenshot.js --url https://example.com --output page.png --no-compress

Compression behavior:

• PNG: Resizes to 90% + quality 85 (or 75% + quality 70 if still too large)
• JPEG: Quality 80 + progressive encoding (or quality 60 if still too large)
• Other formats: Converted to JPEG with compression
• Requires ImageMagick installed (see imagemagick skill)

Output includes compression info:

{
  "success": true,
  "output": "/path/to/page.png",
  "compressed": true,
  "originalSize": 8388608,
  "size": 3145728,
  "compressionRatio": "62.50%",
  "url": "https://example.com"
}

Chain Commands (reuse browser)

# Keep browser open with --close false
bun navigate.js --url https://example.com/login --close false
bun fill.js --selector "#email" --value "user@example.com" --close false
bun fill.js --selector "#password" --value "secret" --close false
bun click.js --selector "button[type=submit]"

Parse JSON Output

# Extract specific fields with jq
bun performance.js --url https://example.com | jq '.vitals.LCP'

# Save to file
bun network.js --url https://example.com --output /tmp/requests.json

Execution Protocol

Working Directory Verification

BEFORE executing any script:

1. Check current working directory with pwd
2. Verify in .claude/skills/chrome-devtools/scripts/ directory
3. If wrong directory, cd to correct location
4. Use absolute paths for all output files

Example:

pwd  # Should show: .../chrome-devtools/scripts
# If wrong:
cd .claude/skills/chrome-devtools/scripts

Output Validation

AFTER screenshot/capture operations:

1. Verify file created with ls -lh <output-path>
2. Read screenshot using Read tool to confirm content
3. Check JSON output for success:true
4. Report file size and compression status

Example:

bun screenshot.js --url https://example.com --output ./docs/screenshots/page.png
ls -lh ./docs/screenshots/page.png  # Verify file exists
# Then use Read tool to visually inspect

5. Restart working directory to the project root.

Error Recovery

If script fails:

1. Check error message for selector issues
2. Use snapshot.js to discover correct selectors
3. Try XPath selector if CSS selector fails
4. Verify element is visible and interactive

Example:

# CSS selector fails
bun click.js --url https://example.com --selector ".btn-submit"
# Error: waiting for selector ".btn-submit" failed

# Discover correct selector
bun snapshot.js --url https://example.com | jq '.elements[] | select(.tagName=="BUTTON")'

# Try XPath
bun click.js --url https://example.com --selector "//button[contains(text(),'Submit')]"

Common Options

All scripts support:

• --headless false - Show browser window (default: true)
• --close false - Keep browser open after script
• --timeout 30000 - Timeout in milliseconds (default: 30000)
• --help - Show script-specific help

Troubleshooting

Browser fails to launch (Linux):

./install-deps.sh  # Install missing system libraries

Large screenshots:

• Enable ImageMagick for automatic compression
• Use --max-size to set custom threshold
• Or capture specific element instead of full page

Element not found:

• Use snapshot.js first to discover selectors
• Check if element is dynamically loaded (wait longer)
• Try XPath if CSS fails

Script not found:

• Verify you're in the correct directory
• Check script name spelling
• Use absolute path: bun /path/to/scripts/navigate.js

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