Playwright Skill

---
name: playwright-skill
description: General-purpose browser automation skill. Use when a task needs custom Playwright code — end-to-end testing, scraping a JS-rendered page, or driving a browser interactively — executed via this skill's universal executor rather than a one-off script.
category: library
risk: unknown
source: lackeyjb (MIT)
date_added: "2026-02-27"
plugin:
  setup:
    type: manual
    summary: "Run `npm run setup` in the skill directory before first use to install Playwright and Chromium."
    docs: "SKILL.md"
---

**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: `<plugin-root>/skills/playwright-skill`
- Manual global: `<agent-home>/skills/playwright-skill`
- Project-specific: `<project>/.agent/skills/playwright-skill`

# 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:

   ```bash
   cd $SKILL_DIR && node -e "require('./lib/helpers').detectDevServers().then(servers => console.log(JSON.stringify(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-*.js`

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-*.js` (won't clutter your project)
4. I execute it via: `cd $SKILL_DIR && node run.js /tmp/playwright-test-*.js`
5. Results displayed in real-time, browser window visible for debugging
6. Test files auto-cleaned from /tmp by your OS

## Setup (First Time)

```bash
cd $SKILL_DIR
npm run setup
```

This installs Playwright and Chromium browser. Only needed once.

## Execution Pattern

**Step 1: Detect dev servers (for localhost testing)**

```bash
cd $SKILL_DIR && node -e "require('./lib/helpers').detectDevServers().then(s => console.log(JSON.stringify(s)))"
```

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

```javascript
// /tmp/playwright-test-page.js
const { chromium } = require('playwright');

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

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

  await page.goto(TARGET_URL);
  console.log('Page loaded:', await page.title());

  await page.screenshot({ path: '/tmp/screenshot.png', fullPage: true });
  console.log('📸 Screenshot saved to /tmp/screenshot.png');

  await browser.close();
})();
```

**Step 3: Execute from skill directory**

```bash
cd $SKILL_DIR && node run.js /tmp/playwright-test-page.js
```

## Common Patterns

### Test a Page (Multiple Viewports)

```javascript
// /tmp/playwright-test-responsive.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3001'; // Auto-detected

(async () => {
  const browser = await chromium.launch({ headless: false, slowMo: 100 });
  const page = await browser.newPage();

  // Desktop test
  await page.setViewportSize({ width: 1920, height: 1080 });
  await page.goto(TARGET_URL);
  console.log('Desktop - Title:', await page.title());
  await page.screenshot({ path: '/tmp/desktop.png', fullPage: true });

  // Mobile test
  await page.setViewportSize({ width: 375, height: 667 });
  await page.screenshot({ path: '/tmp/mobile.png', fullPage: true });

  await browser.close();
})();
```

### Test Login Flow

```javascript
// /tmp/playwright-test-login.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3001'; // Auto-detected

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

  await page.goto(`${TARGET_URL}/login`);

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

  // Wait for redirect
  await page.waitForURL('**/dashboard');
  console.log('✅ Login successful, redirected to dashboard');

  await browser.close();
})();
```

### Fill and Submit Form

```javascript
// /tmp/playwright-test-form.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3001'; // Auto-detected

(async () => {
  const browser = await chromium.launch({ headless: false, slowMo: 50 });
  const page = await browser.newPage();

  await page.goto(`${TARGET_URL}/contact`);

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

  // Verify submission
  await page.waitForSelector('.success-message');
  console.log('✅ Form submitted successfully');

  await browser.close();
})();
```

### Check for Broken Links

```javascript
const { chromium } = require('playwright');

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

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

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

  for (const link of links) {
    const href = await link.getAttribute('href');
    try {
      const response = await page.request.head(href);
      if (response.ok()) {
        results.working++;
      } else {
        results.broken.push({ url: href, status: response.status() });
      }
    } catch (e) {
      results.broken.push({ url: href, error: e.message });
    }
  }

  console.log(`✅ Working links: ${results.working}`);
  console.log(`❌ Broken links:`, results.broken);

  await browser.close();
})();
```

### Take Screenshot with Error Handling

```javascript
const { chromium } = require('playwright');

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

  try {
    await page.goto('http://localhost:3000', {
      waitUntil: 'networkidle',
      timeout: 10000,
    });

    await page.screenshot({
      path: '/tmp/screenshot.png',
      fullPage: true,
    });

    console.log('📸 Screenshot saved to /tmp/screenshot.png');
  } catch (error) {
    console.error('❌ Error:', error.message);
  } finally {
    await browser.close();
  }
})();
```

### Test Responsive Design

```javascript
// /tmp/playwright-test-responsive-full.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3001'; // Auto-detected

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

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

  for (const viewport of viewports) {
    console.log(
      `Testing ${viewport.name} (${viewport.width}x${viewport.height})`,
    );

    await page.setViewportSize({
      width: viewport.width,
      height: viewport.height,
    });

    await page.goto(TARGET_URL);
    await page.waitForTimeout(1000);

    await page.screenshot({
      path: `/tmp/${viewport.name.toLowerCase()}.png`,
      fullPage: true,
    });
  }

  console.log('✅ All viewports tested');
  await browser.close();
})();
```

## Inline Execution (Simple Tasks)

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

```bash
# Take a quick screenshot
cd $SKILL_DIR && node run.js "
const browser = await chromium.launch({ headless: false });
const page = await browser.newPage();
await page.goto('http://localhost:3001');
await page.screenshot({ path: '/tmp/quick-screenshot.png', fullPage: true });
console.log('Screenshot saved');
await 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.js`:

```javascript
const helpers = require('./lib/helpers');

// Detect running dev servers (CRITICAL - use this first!)
const servers = await helpers.detectDevServers();
console.log('Found servers:', servers);

// Safe click with retry
await helpers.safeClick(page, 'button.submit', { retries: 3 });

// Safe type with clear
await helpers.safeType(page, '#username', 'testuser');

// Take timestamped screenshot
await helpers.takeScreenshot(page, 'test-result');

// Handle cookie banners
await helpers.handleCookieBanner(page);

// Extract table data
const data = await helpers.extractTableData(page, 'table.results');
```

See `lib/helpers.js` 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):**

```bash
PW_HEADER_NAME=X-Automated-By PW_HEADER_VALUE=playwright-skill \
  cd $SKILL_DIR && node run.js /tmp/my-script.js
```

**Multiple headers (JSON format):**

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

### How It Works

Headers are automatically applied when using `helpers.createContext()`:

```javascript
const context = await helpers.createContext(browser);
const page = await context.newPage();
// All requests from this page include your custom headers
```

For scripts using raw Playwright API, use the injected `getContextOptionsWithHeaders()`:

```javascript
const context = await browser.newContext(
  getContextOptionsWithHeaders({ viewport: { width: 1920, height: 1080 } }),
);
```

## Advanced Usage

For comprehensive Playwright API documentation, see [API_REFERENCE.md](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 `detectDevServers()` 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-*.js`, 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 `slowMo: 100` to make actions visible and easier to follow
- **Wait strategies:** Use `waitForURL`, `waitForSelector`, `waitForLoadState` instead of fixed timeouts
- **Error handling:** Always use try-catch for robust automation
- **Console output:** Use `console.log()` to track progress and show what's happening

## Troubleshooting

**Playwright not installed:**

```bash
cd $SKILL_DIR && npm run setup
```

**Module not found:**
Ensure running from skill directory via `run.js` wrapper

**Browser doesn't open:**
Check `headless: false` and ensure display available

**Element not found:**
Add wait: `await page.waitForSelector('.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: detectDevServers()]
[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.js with URL parameterized]
[Runs: cd $SKILL_DIR && node run.js /tmp/playwright-test-marketing.js]
[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: detectDevServers()]
[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.js]
[Runs: cd $SKILL_DIR && node run.js /tmp/playwright-test-login.js]
[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.js`
- Progressive disclosure - API_REFERENCE.md loaded only when advanced features needed

## When to Use
This skill is applicable to execute the workflow or actions described in the overview.

## Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.