Chrome Devtools
Browser automation, debugging, and performance analysis using Puppeteer CLI scripts. Use for automating browsers, taking screenshots, analyzing performance, monitoring network traffic, web scraping, f
Chrome Devtools
Version: 1.1.0 | License: Apache-2.0
Chrome DevTools Agent Skill
Browser automation via Puppeteer scripts with persistent sessions. All scripts output JSON.
Skill Location
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
# Detect skill location
SKILL_DIR=""
if [ -d ".claude/skills/chrome-devtools/scripts" ]; then
SKILL_DIR=".claude/skills/chrome-devtools/scripts"
elif [ -d "$HOME/.claude/skills/chrome-devtools/scripts" ]; then
SKILL_DIR="$HOME/.claude/skills/chrome-devtools/scripts"
fi
cd "$SKILL_DIR"Choosing Your Approach
| Scenario | Approach |
|---|---|
| Source-available sites | Read source code first, write selectors directly |
| Unknown layouts | Use aria-snapshot.js for semantic discovery |
| Visual inspection | Take screenshots to verify rendering |
| Debug issues | Collect console logs, analyze with session storage |
| Accessibility audit | Use ARIA snapshot for semantic structure analysis |
Automation Browsing Running Mode
- Detect current OS and launch browser as headless only when running on Linux, WSL, or CI environments.
- For macOS/Windows, browser always runs in headed mode for better debugging.
- Run multiple scripts/sessions in parallel to simulate real user interactions.
- Run multiple scripts/sessions in parallel to simulate different device types (mobile, tablet, desktop).
- Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
ARIA Snapshot (Element Discovery)
When page structure is unknown, use aria-snapshot.js to get a YAML-formatted accessibility tree with semantic roles, accessible names, states, and stable element references.
Get ARIA Snapshot
# Generate ARIA snapshot and output to stdout
node aria-snapshot.js --url https://example.com
# Save to file in snapshots directory
node aria-snapshot.js --url https://example.com --output ./.claude/chrome-devtools/snapshots/page.yamlExample YAML Output
- banner:
- link "Hacker News" [ref=e1]
/url: https://news.ycombinator.com
- navigation:
- link "new" [ref=e2]
- link "past" [ref=e3]
- link "comments" [ref=e4]
- main:
- list:
- listitem:
- link "Show HN: My new project" [ref=e8]
- text: "128 points by user 3 hours ago"
- contentinfo:
- textbox [ref=e10]
/placeholder: "Search"Interpreting ARIA Notation
| Notation | Meaning |
|---|---|
[ref=eN] | Stable identifier for interactive elements |
[checked] | Checkbox/radio is selected |
[disabled] | Element is inactive |
[expanded] | Accordion/dropdown is open |
[level=N] | Heading hierarchy (1-6) |
/url: | Link destination |
/placeholder: | Input placeholder text |
/value: | Current input value |
Interact by Ref
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
Use select-ref.js to interact with elements by their ref:
# Click element with ref e5
node select-ref.js --ref e5 --action click
# Fill input with ref e10
node select-ref.js --ref e10 --action fill --value "search query"
# Get text content
node select-ref.js --ref e8 --action text
# Screenshot specific element
node select-ref.js --ref e1 --action screenshot --output ./logo.png
# Focus element
node select-ref.js --ref e10 --action focus
# Hover over element
node select-ref.js --ref e5 --action hoverStore Snapshots
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
Store snapshots for analysis in <project>/.claude/chrome-devtools/snapshots/:
# Create snapshots directory
mkdir -p .claude/chrome-devtools/snapshots
# Capture and store with timestamp
SESSION="$(date +%Y%m%d-%H%M%S)"
node aria-snapshot.js --url https://example.com --output .claude/chrome-devtools/snapshots/$SESSION.yamlWorkflow: Unknown Page Structure
-
Get snapshot to discover elements:
node aria-snapshot.js --url https://example.com -
Identify target from YAML output (e.g.,
[ref=e5]for a button) -
Interact by ref:
node select-ref.js --ref e5 --action click -
Verify result with screenshot or new snapshot:
node screenshot.js --output ./result.png
Local HTML Files
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
IMPORTANT: Never browse local HTML files via file:// protocol. Always serve via local server:
Why: file:// protocol blocks many browser features (CORS, ES modules, fetch API, service workers). Local server ensures proper HTTP behavior.
# Option 1: npx serve (recommended)
npx serve ./dist -p 3000 &
node navigate.js --url http://localhost:3000
# Option 2: Python http.server
python -m http.server 3000 --directory ./dist &
node navigate.js --url http://localhost:3000Note: when port 3000 is busy, find an available port with lsof -i :3000 and use a different one.
Quick Start
# Install dependencies
cd .claude/skills/chrome-devtools/scripts
npm install # Installs puppeteer, sharp, debug, yargs
# Test (browser stays running for session reuse)
node navigate.js --url https://example.com
# Output: {"success": true, "url": "...", "title": "..."}Linux/WSL only: Run ./install-deps.sh first for Chrome system libraries.
Session Persistence
Browser state persists across script executions via WebSocket endpoint file (.browser-session.json).
Default behavior: Scripts disconnect but keep browser running for session reuse.
# First script: launches browser, navigates, disconnects (browser stays running)
node navigate.js --url https://example.com/login
# Subsequent scripts: connect to existing browser, reuse page state
node fill.js --selector "#email" --value "user@example.com"
node fill.js --selector "#password" --value "secret"
node click.js --selector "button[type=submit]"
# Close browser when done
node navigate.js --url about:blank --close trueSession management:
--close true: Close browser and clear session- Default (no flag): Keep browser running for next script
Available Scripts
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
All in .claude/skills/chrome-devtools/scripts/:
| Script | Purpose |
|---|---|
navigate.js | Navigate to URLs |
screenshot.js | Capture screenshots (auto-compress >5MB via Sharp) |
click.js | Click elements |
fill.js | Fill form fields |
evaluate.js | Execute JS in page context |
snapshot.js | Extract interactive elements (JSON format) |
aria-snapshot.js | Get ARIA accessibility tree (YAML format with refs) |
select-ref.js | Interact with elements by ref from ARIA snapshot |
console.js | Monitor console messages/errors |
network.js | Track HTTP requests/responses |
performance.js | Measure Core Web Vitals |
Workflow Loop
- Execute focused script for single task
- Observe JSON output
- Assess completion status
- Decide next action
- Repeat until done
Writing Custom Test Scripts
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
For complex automation, write scripts to <project>/.claude/chrome-devtools/tmp/:
# Create tmp directory for test scripts
mkdir -p $SKILL_DIR/.claude/chrome-devtools/tmp
# Write a test script
cat > $SKILL_DIR/.claude/chrome-devtools/tmp/login-test.js << 'EOF'
import { getBrowser, getPage, disconnectBrowser, outputJSON } from '../scripts/lib/browser.js';
async function loginTest() {
const browser = await getBrowser();
const page = await getPage(browser);
await page.goto('https://example.com/login');
await page.type('#email', 'user@example.com');
await page.type('#password', 'secret');
await page.click('button[type=submit]');
await page.waitForNavigation();
outputJSON({
success: true,
url: page.url(),
title: await page.title()
});
await disconnectBrowser();
}
loginTest();
EOF
# Run the test
node $SKILL_DIR/.claude/chrome-devtools/tmp/login-test.jsKey principles for custom scripts:
- Single-purpose: one script, one task
- Always call
disconnectBrowser()at the end (keeps browser running) - Use
closeBrowser()only when ending session completely - Output JSON for easy parsing
- Plain JavaScript only in
page.evaluate()callbacks
Screenshots
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
Store screenshots for analysis in <project>/.claude/chrome-devtools/screenshots/:
# Basic screenshot
node screenshot.js --url https://example.com --output ./.claude/chrome-devtools/screenshots/page.png
# Full page
node screenshot.js --url https://example.com --output ./.claude/chrome-devtools/screenshots/page.png --full-page true
# Specific element
node screenshot.js --url https://example.com --selector ".main-content" --output ./.claude/chrome-devtools/screenshots/element.pngAuto-Compression (Sharp)
Screenshots >5MB auto-compress using Sharp (4-5x faster than ImageMagick):
# Default: compress if >5MB
node screenshot.js --url https://example.com --output ./.claude/chrome-devtools/screenshots/page.png
# Custom threshold (3MB)
node screenshot.js --url https://example.com --output ./.claude/chrome-devtools/screenshots/page.png --max-size 3
# Disable compression
node screenshot.js --url https://example.com --output ./.claude/chrome-devtools/screenshots/page.png --no-compressStore screenshots for analysis in <project>/.claude/chrome-devtools/screenshots/.
Console Log Collection & Analysis
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
Capture Logs
# Capture all logs for 10 seconds
node console.js --url https://example.com --duration 10000
# Filter by type
node console.js --url https://example.com --types error,warn --duration 5000Session Storage Pattern
Store logs for analysis in <project>/.claude/chrome-devtools/logs/<session>/:
# Create session directory
SESSION="$(date +%Y%m%d-%H%M%S)"
mkdir -p .claude/chrome-devtools/logs/$SESSION
# Capture and store
node console.js --url https://example.com --duration 10000 > .claude/chrome-devtools/logs/$SESSION/console.json
node network.js --url https://example.com > .claude/chrome-devtools/logs/$SESSION/network.json
# View errors
jq '.messages[] | select(.type=="error")' .claude/chrome-devtools/logs/$SESSION/console.jsonRoot Cause Analysis
# 1. Check for JavaScript errors
node console.js --url https://example.com --types error,pageerror --duration 5000 | jq '.messages'
# 2. Correlate with network failures
node network.js --url https://example.com | jq '.requests[] | select(.response.status >= 400)'
# 3. Check specific error stack traces
node console.js --url https://example.com --types error --duration 5000 | jq '.messages[].stack'Finding Elements
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
Use snapshot.js to discover selectors before interacting:
# Get all interactive elements
node snapshot.js --url https://example.com | jq '.elements[] | {tagName, text, selector}'
# Find buttons
node snapshot.js --url https://example.com | jq '.elements[] | select(.tagName=="button")'
# Find by text content
node snapshot.js --url https://example.com | jq '.elements[] | select(.text | contains("Submit"))'Error Recovery
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope. If script fails:
# 1. Capture current state (without navigating to preserve state)
node screenshot.js --output ./.claude/skills/chrome-devtools/screenshots/debug.png
# 2. Get console errors
node console.js --url about:blank --types error --duration 1000
# 3. Discover correct selector
node snapshot.js | jq '.elements[] | select(.text | contains("Submit"))'
# 4. Try XPath if CSS fails
node click.js --selector "//button[contains(text(),'Submit')]"Common Patterns
Web Scraping
node evaluate.js --url https://example.com --script "
Array.from(document.querySelectorAll('.item')).map(el => ({
title: el.querySelector('h2')?.textContent,
link: el.querySelector('a')?.href
}))
" | jq '.result'Form Automation
node navigate.js --url https://example.com/form
node fill.js --selector "#search" --value "query"
node click.js --selector "button[type=submit]"Performance Testing
node performance.js --url https://example.com | jq '.vitals'Script Options
All scripts support:
--headless false- Show browser window--close true- Close browser completely (default: stay running)--timeout 30000- Set timeout (ms)--wait-until networkidle2- Wait strategy Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
Troubleshooting
Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope.
| Error | Solution |
|---|---|
Cannot find package 'puppeteer' | Run npm install in scripts directory |
libnss3.so missing (Linux) | Run ./install-deps.sh |
| Element not found | Use snapshot.js to find correct selector |
| Script hangs | Use --timeout 60000 or --wait-until load |
| Screenshot >5MB | Auto-compressed; use --max-size 3 for lower |
| Session stale | Delete .browser-session.json and retry |
Screenshot Analysis: Missing Images
If images don't appear in screenshots, they may be waiting for animation triggers:
-
Scroll-triggered animations: Scroll element into view first
node evaluate.js --script "document.querySelector('.lazy-image').scrollIntoView()" # Wait for animation node evaluate.js --script "await new Promise(r => setTimeout(r, 1000))" node screenshot.js --output ./result.png -
Sequential animation queue: Wait longer and retry
# First attempt node screenshot.js --url http://localhost:3000 --output ./attempt1.png # Wait for animations to complete node evaluate.js --script "await new Promise(r => setTimeout(r, 2000))" # Retry screenshot node screenshot.js --output ./attempt2.png -
Intersection Observer animations: Trigger by scrolling through page
node evaluate.js --script "window.scrollTo(0, document.body.scrollHeight)" node evaluate.js --script "await new Promise(r => setTimeout(r, 1500))" node evaluate.js --script "window.scrollTo(0, 0)" node screenshot.js --output ./full-loaded.png --full-page true
Reference Documentation
./references/cdp-domains.md- Chrome DevTools Protocol domains./references/puppeteer-reference.md- Puppeteer API patterns./references/performance-guide.md- Core Web Vitals optimization./scripts/README.md- Detailed script options
References
Performance Guide
Reference documentation
Cdp Domains
Reference documentation
Puppeteer Reference
Reference documentation
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