Playwright Py Skill

IMPORTANT - Path Resolution: This skill can be installed in different locations (plugin system, manual installation, global, or project-specific). Before executing any commands, determine the skill directory based on where you loaded this SKILL.md file, and use that path in all commands below. Replace $SKILL_DIR with the actual discovered path.

Common installation paths:

• Plugin system: ~/.claude/plugins/marketplaces/playwright-py-skill/skills/playwright-py-skill
• Manual global: ~/.claude/skills/playwright-py-skill
• Project-specific: <project>/.claude/skills/playwright-py-skill

CRITICAL: Sequential Tool Usage

When writing and executing Playwright scripts, ALWAYS use Write and Bash tools in separate responses:

❌ DO NOT use parallel execution (causes race condition):

Write: create /tmp/playwright-test.py
Bash: uv run run.py /tmp/playwright-test.py  <-- Executes before Write completes!

✅ ALWAYS use sequential execution:

Response 1: Write /tmp/playwright-test.py
Response 2: Bash: cd $SKILL_DIR && uv run run.py /tmp/playwright-test.py

This prevents race conditions where Bash executes before the file is fully written.

Playwright Browser Automation

General-purpose browser automation skill. I'll write custom Playwright code for any automation task you request and execute it via the universal executor.

CRITICAL WORKFLOW - Follow these steps in order:

1. Auto-detect dev servers - For localhost testing, ALWAYS run server detection FIRST:

   cd $SKILL_DIR && uv run python -c "from lib.helpers import detect_dev_servers; import asyncio, json; print(json.dumps(asyncio.run(detect_dev_servers())))"
   

   • If 1 server found: Use it automatically, inform user
   • If multiple servers found: Ask user which one to test
   • If no servers found: Ask for URL or offer to help start dev server

2. Write scripts to /tmp - NEVER write test files to skill directory; always use /tmp/playwright-test-*.py

3. Use visible browser by default - Always use headless=False unless user specifically requests headless mode

4. Parameterize URLs - Always make URLs configurable via environment variable or constant at top of script

How It Works

1. You describe what you want to test/automate
2. I auto-detect running dev servers (or ask for URL if testing external site)
3. I write custom Playwright code in /tmp/playwright-test-*.py (won't clutter your project)
4. I execute it via: cd $SKILL_DIR && uv run run.py /tmp/playwright-test-*.py
5. Results displayed in real-time, browser window visible for debugging
6. Test files auto-cleaned from /tmp by your OS

Setup (First Time)

cd $SKILL_DIR
uv run run.py --help

This will automatically install Playwright via PEP 723 metadata. Chromium browser must already be installed (correct version for Playwright 1.56.0).

Execution Pattern

Step 1: Detect dev servers (for localhost testing)

cd $SKILL_DIR && uv run python -c "from lib.helpers import detect_dev_servers; import asyncio, json; print(json.dumps(asyncio.run(detect_dev_servers())))"

Step 2: Write test script to /tmp with URL parameter

#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "playwright==1.56.0",
# ]
# ///
# /tmp/playwright-test-page.py
from playwright.sync_api import sync_playwright

# Parameterized URL (detected or user-provided)
TARGET_URL = 'http://localhost:3001'  # <-- Auto-detected or from user

with sync_playwright() as p:
    browser = p.chromium.launch(headless=False)
    page = browser.new_page()

    page.goto(TARGET_URL)
    print('Page loaded:', page.title())

    page.screenshot(path='/tmp/screenshot.png', full_page=True)
    print('📸 Screenshot saved to /tmp/screenshot.png')

    browser.close()

Step 3: Execute from skill directory

cd $SKILL_DIR && uv run run.py /tmp/playwright-test-page.py

Common Patterns

Test a Page (Multiple Viewports)

#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "playwright==1.56.0",
# ]
# ///
# /tmp/playwright-test-responsive.py
from playwright.sync_api import sync_playwright

TARGET_URL = 'http://localhost:3001'  # Auto-detected

with sync_playwright() as p:
    browser = p.chromium.launch(headless=False, slow_mo=100)
    page = browser.new_page()

    # Desktop test
    page.set_viewport_size({'width': 1920, 'height': 1080})
    page.goto(TARGET_URL)
    print('Desktop - Title:', page.title())
    page.screenshot(path='/tmp/desktop.png', full_page=True)

    # Mobile test
    page.set_viewport_size({'width': 375, 'height': 667})
    page.screenshot(path='/tmp/mobile.png', full_page=True)

    browser.close()

Test Login Flow

#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "playwright==1.56.0",
# ]
# ///
# /tmp/playwright-test-login.py
from playwright.sync_api import sync_playwright

TARGET_URL = 'http://localhost:3001'  # Auto-detected

with sync_playwright() as p:
    browser = p.chromium.launch(headless=False)
    page = browser.new_page()

    page.goto(f'{TARGET_URL}/login')

    page.fill('input[name="email"]', 'test@example.com')
    page.fill('input[name="password"]', 'password123')
    page.click('button[type="submit"]')

    # Wait for redirect
    page.wait_for_url('**/dashboard')
    print('✅ Login successful, redirected to dashboard')

    browser.close()

Fill and Submit Form

#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "playwright==1.56.0",
# ]
# ///
# /tmp/playwright-test-form.py
from playwright.sync_api import sync_playwright

TARGET_URL = 'http://localhost:3001'  # Auto-detected

with sync_playwright() as p:
    browser = p.chromium.launch(headless=False, slow_mo=50)
    page = browser.new_page()

    page.goto(f'{TARGET_URL}/contact')

    page.fill('input[name="name"]', 'John Doe')
    page.fill('input[name="email"]', 'john@example.com')
    page.fill('textarea[name="message"]', 'Test message')
    page.click('button[type="submit"]')

    # Verify submission
    page.wait_for_selector('.success-message')
    print('✅ Form submitted successfully')

    browser.close()

Check for Broken Links

#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "playwright==1.56.0",
# ]
# ///
from playwright.sync_api import sync_playwright

with sync_playwright() as p:
    browser = p.chromium.launch(headless=False)
    page = browser.new_page()

    page.goto('http://localhost:3000')

    links = page.locator('a[href^="http"]').all()
    results = {'working': 0, 'broken': []}

    for link in links:
        href = link.get_attribute('href')
        try:
            response = page.request.head(href)
            if response.ok:
                results['working'] += 1
            else:
                results['broken'].append({'url': href, 'status': response.status})
        except Exception as e:
            results['broken'].append({'url': href, 'error': str(e)})

    print(f'✅ Working links: {results["working"]}')
    print(f'❌ Broken links:', results['broken'])

    browser.close()

Take Screenshot with Error Handling

#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "playwright==1.56.0",
# ]
# ///
from playwright.sync_api import sync_playwright

with sync_playwright() as p:
    browser = p.chromium.launch(headless=False)
    page = browser.new_page()

    try:
        page.goto('http://localhost:3000', wait_until='networkidle', timeout=10000)

        page.screenshot(path='/tmp/screenshot.png', full_page=True)

        print('📸 Screenshot saved to /tmp/screenshot.png')
    except Exception as error:
        print(f'❌ Error: {error}')
    finally:
        browser.close()

Test Responsive Design

#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "playwright==1.56.0",
# ]
# ///
# /tmp/playwright-test-responsive-full.py
from playwright.sync_api import sync_playwright

TARGET_URL = 'http://localhost:3001'  # Auto-detected

with sync_playwright() as p:
    browser = p.chromium.launch(headless=False)
    page = browser.new_page()

    viewports = [
        {'name': 'Desktop', 'width': 1920, 'height': 1080},
        {'name': 'Tablet', 'width': 768, 'height': 1024},
        {'name': 'Mobile', 'width': 375, 'height': 667},
    ]

    for viewport in viewports:
        print(f'Testing {viewport["name"]} ({viewport["width"]}x{viewport["height"]})')

        page.set_viewport_size({'width': viewport['width'], 'height': viewport['height']})

        page.goto(TARGET_URL)
        page.wait_for_timeout(1000)

        page.screenshot(path=f'/tmp/{viewport["name"].lower()}.png', full_page=True)

    print('✅ All viewports tested')
    browser.close()

Inline Execution (Simple Tasks)

For quick one-off tasks, you can execute code inline without creating files:

# Take a quick screenshot
cd $SKILL_DIR && uv run run.py "
with sync_playwright() as p:
    browser = p.chromium.launch(headless=False)
    page = browser.new_page()
    page.goto('http://localhost:3001')
    page.screenshot(path='/tmp/quick-screenshot.png', full_page=True)
    print('Screenshot saved')
    browser.close()
"

When to use inline vs files:

• Inline: Quick one-off tasks (screenshot, check if element exists, get page title)
• Files: Complex tests, responsive design checks, anything user might want to re-run

Available Helpers

Optional utility functions in lib/helpers.py:

from lib.helpers import *

# Detect running dev servers (CRITICAL - use this first!)
servers = await detect_dev_servers()
print('Found servers:', servers)

# Safe click with retry
safe_click(page, 'button.submit', retries=3)

# Safe type with clear
safe_type(page, '#username', 'testuser')

# Take timestamped screenshot
take_screenshot(page, 'test-result')

# Handle cookie banners
handle_cookie_banner(page)

# Extract table data
data = extract_table_data(page, 'table.results')

See lib/helpers.py for full list.

Custom HTTP Headers

Configure custom headers for all HTTP requests via environment variables. Useful for:

• Identifying automated traffic to your backend
• Getting LLM-optimized responses (e.g., plain text errors instead of styled HTML)
• Adding authentication tokens globally

Configuration

Single header (common case):

PW_HEADER_NAME=X-Automated-By PW_HEADER_VALUE=playwright-py-skill \
  cd $SKILL_DIR && uv run run.py /tmp/my-script.py

Multiple headers (JSON format):

PW_EXTRA_HEADERS='{"X-Automated-By":"playwright-py-skill","X-Debug":"true"}' \
  cd $SKILL_DIR && uv run run.py /tmp/my-script.py

How It Works

Headers are automatically applied when using create_context():

context = create_context(browser)
page = context.new_page()
# All requests from this page include your custom headers

For scripts using raw Playwright API, use the get_context_options_with_headers():

context = browser.new_context(
    get_context_options_with_headers({'viewport': {'width': 1920, 'height': 1080}})
)

Advanced Usage

For comprehensive Playwright API documentation, see API_REFERENCE.md:

• Selectors & Locators best practices
• Network interception & API mocking
• Authentication & session management
• Visual regression testing
• Mobile device emulation
• Performance testing
• Debugging techniques
• CI/CD integration

Tips

• CRITICAL: Detect servers FIRST - Always run detect_dev_servers() before writing test code for localhost testing
• Custom headers - Use PW_HEADER_NAME/PW_HEADER_VALUE env vars to identify automated traffic to your backend
• Use /tmp for test files - Write to /tmp/playwright-test-*.py, never to skill directory or user's project
• Parameterize URLs - Put detected/provided URL in a TARGET_URL constant at the top of every script
• DEFAULT: Visible browser - Always use headless=False unless user explicitly asks for headless mode
• Headless mode - Only use headless=True when user specifically requests "headless" or "background" execution
• Slow down: Use slow_mo=100 to make actions visible and easier to follow
• Wait strategies: Use wait_for_url, wait_for_selector, wait_for_load_state instead of fixed timeouts
• Error handling: Always use try-catch for robust automation
• Console output: Use print() to track progress and show what's happening

Troubleshooting

Playwright not installed:

cd $SKILL_DIR && uv run run.py --help
# This will auto-install playwright==1.56.0 via PEP 723

Module not found: Ensure running from skill directory via run.py wrapper

Browser doesn't open: Check headless=False and ensure display available

Element not found: Add wait: page.wait_for_selector('.element', timeout=10000)

Example Usage

User: "Test if the marketing page looks good"

Claude: I'll test the marketing page across multiple viewports. Let me first detect running servers...
[Runs: detect_dev_servers()]
[Output: Found server on port 3001]
I found your dev server running on http://localhost:3001

[Writes custom automation script to /tmp/playwright-test-marketing.py with URL parameterized]
[Runs: cd $SKILL_DIR && uv run run.py /tmp/playwright-test-marketing.py]
[Shows results with screenshots from /tmp/]

User: "Check if login redirects correctly"

Claude: I'll test the login flow. First, let me check for running servers...
[Runs: detect_dev_servers()]
[Output: Found servers on ports 3000 and 3001]
I found 2 dev servers. Which one should I test?
- http://localhost:3000
- http://localhost:3001

User: "Use 3001"

[Writes login automation to /tmp/playwright-test-login.py]
[Runs: cd $SKILL_DIR && uv run run.py /tmp/playwright-test-login.py]
[Reports: ✅ Login successful, redirected to /dashboard]

Notes

• Each automation is custom-written for your specific request
• Not limited to pre-built scripts - any browser task possible
• Auto-detects running dev servers to eliminate hardcoded URLs
• Test scripts written to /tmp for automatic cleanup (no clutter)
• Code executes reliably with proper module resolution via run.py
• Progressive disclosure - API_REFERENCE.md loaded only when advanced features needed
• Chromium browser must be installed separately (correct version for Playwright 1.56.0)