Browser Automation

Browser Automation

Use Playwright or Puppeteer MCP for browser automation when WebFetch isn't sufficient.

Overview

Browser automation provides headless browser control for:

• JS-rendered content extraction
• Screenshot capture
• Form filling and submission
• Interactive testing
• Auth-protected page access

MCP Servers

Playwright (Recommended)

Multi-browser support: Firefox, Chrome, WebKit. Same API across all browsers.

Package: @anthropic/mcp-server-playwright Transport: stdio Install: claude mcp add playwright -- npx -y @anthropic/mcp-server-playwright

# Also install browser binaries
npx playwright install firefox chromium webkit

Puppeteer (Chrome Only)

Package: puppeteer-mcp-server Transport: stdio Install: claude mcp add puppeteer -- npx -y puppeteer-mcp-server

Comparison

Available Tools

Navigation

puppeteer_navigate Navigate to a URL and wait for page load.

url: "https://example.com"
waitUntil: "networkidle0" | "domcontentloaded" | "load"

Screenshots

puppeteer_screenshot Capture the current page or specific element.

name: "screenshot-name"
selector: "#element-id"  (optional, full page if omitted)
fullPage: true  (optional)

Interaction

puppeteer_click Click an element by CSS selector.

selector: "button.submit"

puppeteer_fill Fill an input field with text.

selector: "input[name=email]"
value: "user@example.com"

puppeteer_select Select an option from a dropdown.

selector: "select#country"
value: "US"

puppeteer_hover Hover over an element (for tooltips, dropdowns).

selector: ".menu-trigger"

JavaScript Execution

puppeteer_evaluate Run JavaScript in the page context and return results.

script: "document.title"

Usage Patterns

Extract JS-Rendered Content

1. puppeteer_navigate(url="https://spa-app.com/data")
2. puppeteer_evaluate(script="JSON.stringify(window.__DATA__)")

Fill and Submit Form

1. puppeteer_navigate(url="https://example.com/login")
2. puppeteer_screenshot(name="before-login")
3. puppeteer_fill(selector="input[name=email]", value="user@example.com")
4. puppeteer_fill(selector="input[name=password]", value="secret")
5. puppeteer_click(selector="button[type=submit]")
6. puppeteer_screenshot(name="after-login")

Capture Visual Evidence

1. puppeteer_navigate(url="https://example.com")
2. puppeteer_screenshot(name="homepage", fullPage=true)
3. puppeteer_click(selector=".open-modal")
4. puppeteer_screenshot(name="modal-open")

Decision Tree

Need web content?
    │
    ├─ Static HTML? ──────────────────→ WebFetch
    │
    ├─ JS-rendered (React, Vue, etc.)? → Puppeteer
    │
    ├─ Need screenshot? ──────────────→ Puppeteer
    │
    ├─ Need to fill forms? ───────────→ Puppeteer
    │
    ├─ Auth-protected? ───────────────→ Puppeteer (can maintain session)
    │
    └─ Default ───────────────────────→ WebFetch (simpler, faster)

Error Handling

Element Not Found

If a selector doesn't match:

1. Take screenshot to see current page state
2. Use puppeteer_evaluate to check DOM
3. Try alternative selectors
4. Add wait time for dynamic content

Timeout

If page takes too long:

1. Try waitUntil: "domcontentloaded" instead of networkidle0
2. Check if site blocks automation
3. Look for loading spinners/skeleton screens

Session Management

• Browser sessions persist within the conversation
• Use for multi-step flows (login → navigate → action)
• Session cleared on conversation end

Comparison with WebFetch

Best Practices

1. Screenshot liberally - Visual evidence helps debugging
2. Use specific selectors - IDs are most reliable
3. Wait for content - Dynamic sites need time to load
4. Handle failures gracefully - Not all elements exist
5. Close when done - Don't leave orphan sessions

Troubleshooting

"Element not found"

• Page may not be fully loaded
• Selector may be wrong
• Element may be in iframe

"Navigation timeout"

• Site may be slow
• Site may block headless browsers
• Network issues

"Click had no effect"

• Element may be covered by overlay
• May need to scroll into view
• May need to wait for animation