Ck:chrome Devtools

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 (no cd needed - scripts use __dirname for paths)
SKILL_DIR=""
if [ -d ".agents/skills/chrome-devtools/scripts" ]; then
  SKILL_DIR=".agents/skills/chrome-devtools/scripts"
elif [ -d "$HOME/.codex/skills/chrome-devtools/scripts" ]; then
  SKILL_DIR="$HOME/.codex/skills/chrome-devtools/scripts"
fi
# Run scripts with full path: node "$SKILL_DIR/script.js" --args

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

Browser visibility is resolved automatically by resolveHeadless() in lib/browser.js:

| Environment | Default | Why | |-------------|---------|-----| | macOS / Windows | Headed (visible) | Better debugging, OAuth login support | | Linux / WSL | Headless | Servers typically have no display | | CI (CI, GITHUB_ACTIONS, GITLAB_CI, JENKINS_URL env vars) | Headless | No display available |

Override with --headless true or --headless false on any script.

• 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).

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 "$SKILL_DIR/aria-snapshot.js" --url https://example.com

# Save to file in snapshots directory
node "$SKILL_DIR/aria-snapshot.js" --url https://example.com --output ./.codex/chrome-devtools/snapshots/page.yaml

Example 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 "$SKILL_DIR/select-ref.js" --ref e5 --action click

# Fill input with ref e10
node "$SKILL_DIR/select-ref.js" --ref e10 --action fill --value "search query"

# Get text content
node "$SKILL_DIR/select-ref.js" --ref e8 --action text

# Screenshot specific element
node "$SKILL_DIR/select-ref.js" --ref e1 --action screenshot --output ./logo.png

# Focus element
node "$SKILL_DIR/select-ref.js" --ref e10 --action focus

# Hover over element
node "$SKILL_DIR/select-ref.js" --ref e5 --action hover

Store Snapshots

Skills can exist in project-scope or user-scope. Priority: project-scope > user-scope. Store snapshots for analysis in /.codex/chrome-devtools/snapshots/:

# Create snapshots directory
mkdir -p .codex/chrome-devtools/snapshots

# Capture and store with timestamp
SESSION="$(date +%Y%m%d-%H%M%S)"
node "$SKILL_DIR/aria-snapshot.js" --url https://example.com --output .codex/chrome-devtools/snapshots/$SESSION.yaml

Workflow: Unknown Page Structure

1. Get snapshot to discover elements:

``bash node "$SKILL_DIR/aria-snapshot.js" --url https://example.com ``

1. Identify target from YAML output (e.g., [ref=e5] for a button)

1. Interact by ref:

``bash node "$SKILL_DIR/select-ref.js" --ref e5 --action click ``

1. Verify result with screenshot or new snapshot:

``bash node "$SKILL_DIR/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 "$SKILL_DIR/navigate.js" --url http://localhost:3000

# Option 2: Python http.server
python -m http.server 3000 --directory ./dist &
node "$SKILL_DIR/navigate.js" --url http://localhost:3000

Note: when port 3000 is busy, find an available port with lsof -i :3000 and use a different one.

Quick Start

# Install dependencies (one-time setup)
npm install --prefix "$SKILL_DIR"

# Test (browser stays running for session reuse)
node "$SKILL_DIR/navigate.js" --url https://example.com
# Output: {"success": true, "url": "...", "title": "..."}

Linux/WSL only: Run "$SKILL_DIR/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 "$SKILL_DIR/navigate.js" --url https://example.com/login

# Subsequent scripts: connect to existing browser, reuse page state
node "$SKILL_DIR/fill.js" --selector "#email" --value "user@example.com"
node "$SKILL_DIR/fill.js" --selector "#password" --value "secret"
node "$SKILL_DIR/click.js" --selector "button[type=submit]"

# Close browser when done
node "$SKILL_DIR/navigate.js" --url about:blank --close true

Session 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 .agents/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 | | ws-debug.js | Debug WebSocket connections (basic) | | ws-full-debug.js | Debug WebSocket with full events/frames | | inject-auth.js | Inject cookies/tokens for authentication | | import-cookies.js | Import cookies from JSON/Netscape file | | connect-chrome.js | Connect to Chrome with remote debugging |

Workflow Loop

1. Execute focused script for single task
2. Observe JSON output
3. Assess completion status
4. Decide next action
5. 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 /.codex/chrome-devtools/tmp/:

# Create tmp directory for test scripts
mkdir -p $SKILL_DIR/.codex/chrome-devtools/tmp

# Write a test script
cat > $SKILL_DIR/.codex/chrome-devtools/tmp/login-test.js  user-scope.
Store screenshots for analysis in `/.codex/chrome-devtools/screenshots/`:

```bash
# Basic screenshot
node "$SKILL_DIR/screenshot.js" --url https://example.com --output ./.codex/chrome-devtools/screenshots/page.png

# Full page
node "$SKILL_DIR/screenshot.js" --url https://example.com --output ./.codex/chrome-devtools/screenshots/page.png --full-page true

# Specific element
node "$SKILL_DIR/screenshot.js" --url https://example.com --selector ".main-content" --output ./.codex/chrome-devtools/screenshots/element.png

Auto-Compression (Sharp)

Screenshots >5MB auto-compress using Sharp (4-5x faster than ImageMagick):

# Default: compress if >5MB
node "$SKILL_DIR/screenshot.js" --url https://example.com --output ./.codex/chrome-devtools/screenshots/page.png

# Custom threshold (3MB)
node "$SKILL_DIR/screenshot.js" --url https://example.com --output ./.codex/chrome-devtools/screenshots/page.png --max-size 3

# Disable compression
node "$SKILL_DIR/screenshot.js" --url https://example.com --output ./.codex/chrome-devtools/screenshots/page.png --no-compress

Store screenshots for analysis in /.codex/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 "$SKILL_DIR/console.js" --url https://example.com --duration 10000

# Filter by type
node "$SKILL_DIR/console.js" --url https://example.com --types error,warn --duration 5000

Session Storage Pattern

Store logs for analysis in /.codex/chrome-devtools/logs//:

# Create session directory
SESSION="$(date +%Y%m%d-%H%M%S)"
mkdir -p .codex/chrome-devtools/logs/$SESSION

# Capture and store
node "$SKILL_DIR/console.js" --url https://example.com --duration 10000 > .codex/chrome-devtools/logs/$SESSION/console.json
node "$SKILL_DIR/network.js" --url https://example.com > .codex/chrome-devtools/logs/$SESSION/network.json

# View errors
jq '.messages[] | select(.type=="error")' .codex/chrome-devtools/logs/$SESSION/console.json

Root Cause Analysis

# 1. Check for JavaScript errors
node "$SKILL_DIR/console.js" --url https://example.com --types error,pageerror --duration 5000 | jq '.messages'

# 2. Correlate with network failures
node "$SKILL_DIR/network.js" --url https://example.com | jq '.requests[] | select(.response.status >= 400)'

# 3. Check specific error stack traces
node "$SKILL_DIR/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 "$SKILL_DIR/snapshot.js" --url https://example.com | jq '.elements[] | {tagName, text, selector}'

# Find buttons
node "$SKILL_DIR/snapshot.js" --url https://example.com | jq '.elements[] | select(.tagName=="button")'

# Find by text content
node "$SKILL_DIR/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 "$SKILL_DIR/screenshot.js" --output ./.agents/skills/chrome-devtools/screenshots/debug.png

# 2. Get console errors
node "$SKILL_DIR/console.js" --url about:blank --types error --duration 1000

# 3. Discover correct selector
node "$SKILL_DIR/snapshot.js" | jq '.elements[] | select(.text | contains("Submit"))'

# 4. Try XPath if CSS fails
node "$SKILL_DIR/click.js" --selector "//button[contains(text(),'Submit')]"

Common Patterns

Web Scraping

node "$SKILL_DIR/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 "$SKILL_DIR/navigate.js" --url https://example.com/form
node "$SKILL_DIR/fill.js" --selector "#search" --value "query"
node "$SKILL_DIR/click.js" --selector "button[type=submit]"

Performance Testing

node "$SKILL_DIR/performance.js" --url https://example.com | jq '.vitals'

Script Options

All scripts support:

• --headless true/false - Override auto-detected headless mode (default: auto by OS)
• --close true - Close browser completely (default: stay running)
• --timeout 30000 - Set timeout (ms)
• --wait-until networkidle2 - Wait strategy

navigate.js additionally supports:

• --wait-for-login - Interactive login: open headed, wait for URL regex match
• --login-timeout - Max wait for login completion (default: 300000 = 5 min)

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:

1. Scroll-triggered animations: Scroll element into view first

``bash node "$SKILL_DIR/evaluate.js" --script "document.querySelector('.lazy-image').scrollIntoView()" # Wait for animation node "$SKILL_DIR/evaluate.js" --script "await new Promise(r => setTimeout(r, 1000))" node "$SKILL_DIR/screenshot.js" --output ./result.png ``

1. Sequential animation queue: Wait longer and retry

```bash # First attempt node "$SKILL_DIR/screenshot.js" --url http://localhost:3000 --output ./attempt1.png

# Wait for animations to complete node "$SKILL_DIR/evaluate.js" --script "await new Promise(r => setTimeout(r, 2000))"

# Retry screenshot node "$SKILL_DIR/screenshot.js" --output ./attempt2.png ```

1. Intersection Observer animations: Trigger by scrolling through page

``bash node "$SKILL_DIR/evaluate.js" --script "window.scrollTo(0, document.body.scrollHeight)" node "$SKILL_DIR/evaluate.js" --script "await new Promise(r => setTimeout(r, 1500))" node "$SKILL_DIR/evaluate.js" --script "window.scrollTo(0, 0)" node "$SKILL_DIR/screenshot.js" --output ./full-loaded.png --full-page true ``

Authentication & Cookies

For accessing protected/authenticated pages, use one of these methods:

Method 1: Inject Cookies Directly

Use when you have cookie values (from DevTools or manual extraction):

# Inject single cookie
node "$SKILL_DIR/inject-auth.js" --url https://site.com \
  --cookies '[{"name":"session","value":"abc123","domain":".site.com"}]'

# Multiple cookies with all properties
node "$SKILL_DIR/inject-auth.js" --url https://site.com \
  --cookies '[{"name":"session","value":"abc","domain":".site.com","httpOnly":true,"secure":true}]'

# With Bearer token header
node "$SKILL_DIR/inject-auth.js" --url https://api.site.com \
  --token "Bearer eyJhbG..." --header Authorization

Method 2: Import from Browser Extension

Best for complex auth (OAuth, multi-cookie sessions):

# 1. Ins

…

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [manhvann](https://github.com/manhvann)
- **Source:** [manhvann/codexkit](https://github.com/manhvann/codexkit)
- **License:** MIT

Install and usage instructions live in the source repository linked above.