Browsing with Chrome Direct

Overview

Control Chrome via DevTools Protocol using the use_browser MCP tool. Single unified interface with auto-starting Chrome.

Announce: "I'm using the browsing skill to control Chrome."

When to Use

Use this when:

• Controlling authenticated sessions
• Managing multiple tabs in running browser
• Playwright MCP unavailable or excessive

Use Playwright MCP when:

• Need fresh browser instances
• Generating screenshots/PDFs
• Prefer higher-level abstractions

Auto-Capture

Every DOM action (navigate, click, type, select, eval, keyboard_press) automatically saves:

• {prefix}.png — viewport screenshot
• {prefix}.md — page content as structured markdown
• {prefix}.html — full rendered DOM
• {prefix}-console.txt — browser console messages

Files are saved to the session directory with sequential prefixes (001-navigate, 002-click, etc.). You must check these before using extract or screenshot actions.

The use_browser Tool

Single MCP tool with action-based interface. Chrome auto-starts on first use.

Parameters:

• action (required): Operation to perform
• tab_index (optional): Tab to operate on (default: 0)
• selector (optional): CSS selector for element operations
• payload (optional): Action-specific data
• timeout (optional): Timeout in ms for await operations (default: 5000)

Actions Reference

Navigation

• navigate: Navigate to URL

  • payload: URL string
  • Example: {action: "navigate", payload: "https://example.com"}

• await_element: Wait for element to appear

  • selector: CSS selector
  • timeout: Max wait time in ms
  • Example: {action: "await_element", selector: ".loaded", timeout: 10000}

• await_text: Wait for text to appear

  • payload: Text to wait for
  • Example: {action: "await_text", payload: "Welcome"}

Interaction

• click: Click element

  • selector: CSS selector
  • Example: {action: "click", selector: "button.submit"}

• type: Type text into input (append \n to submit)

  • selector: CSS selector
  • payload: Text to type
  • Example: {action: "type", selector: "#email", payload: "user@example.com\n"}

• select: Select dropdown option

  • selector: CSS selector
  • payload: Option value(s)
  • Example: {action: "select", selector: "select[name=state]", payload: "CA"}

Extraction

• extract: Get page content

  • payload: Format ('markdown'|'text'|'html')
  • selector: Optional - limit to element
  • Example: {action: "extract", payload: "markdown"}
  • Example: {action: "extract", payload: "text", selector: "h1"}

• attr: Get element attribute

  • selector: CSS selector
  • payload: Attribute name
  • Example: {action: "attr", selector: "a.download", payload: "href"}

• eval: Execute JavaScript

  • payload: JavaScript code
  • Example: {action: "eval", payload: "document.title"}

Export

• screenshot: Capture screenshot of a specific element
  • payload: Filename
  • selector: Optional - screenshot specific element
  • Viewport screenshots are auto-captured after every DOM action. Use this only when you need a specific element.
  • Example: {action: "screenshot", payload: "/tmp/chart.png", selector: ".chart"}

Tab Management

• list_tabs: List all open tabs

  • Example: {action: "list_tabs"}

• new_tab: Create new tab

  • Example: {action: "new_tab"}

• close_tab: Close tab

  • tab_index: Tab to close
  • Example: {action: "close_tab", tab_index: 2}

Browser Mode Control

• show_browser: Make browser window visible (headed mode)

  • Example: {action: "show_browser"}
  • ⚠️ WARNING: Restarts Chrome, reloads pages via GET, loses POST state

• hide_browser: Switch to headless mode (invisible browser)

  • Example: {action: "hide_browser"}
  • ⚠️ WARNING: Restarts Chrome, reloads pages via GET, loses POST state

• browser_mode: Check current browser mode, port, and profile

  • Example: {action: "browser_mode"}
  • Returns: {"headless": true|false, "mode": "headless"|"headed", "running": true|false, "port": 9222, "profile": "name", "profileDir": "/path"}

Profile Management

• set_profile: Change Chrome profile (must kill Chrome first)

  • Example: {action: "set_profile", "payload": "browser-user"}
  • ⚠️ WARNING: Chrome must be stopped first

• get_profile: Get current profile name and directory

  • Example: {action: "get_profile"}
  • Returns: {"profile": "name", "profileDir": "/path"}

Default behavior: Chrome starts in headless mode with "superpowers-chrome" profile on a dynamically allocated port (range 9222-12111). Override with CHROME_WS_PORT env var or MCP --port=N flag.

Critical caveats when toggling modes:

1. Chrome must restart - Cannot switch headless/headed mode on running Chrome
2. Pages reload via GET - All open tabs are reopened with GET requests
3. POST state is lost - Form submissions, POST results, and POST-based navigation will be lost
4. Session state is lost - Any client-side state (JavaScript variables, etc.) is cleared
5. Cookies/auth may persist - Uses same user data directory, so logged-in sessions may survive

When to use headed mode:

• Debugging visual rendering issues
• Demonstrating browser behavior to user
• Testing features that only work with visible browser
• Debugging issues that don't reproduce in headless mode

When to stay in headless mode (default):

• All other cases - faster, cleaner, less intrusive
• Screenshots work perfectly in headless mode
• Most automation works identically in both modes

Profile management: Profiles store persistent browser data (cookies, localStorage, extensions, auth sessions).

Profile locations:

• macOS: ~/Library/Caches/superpowers/browser-profiles/{name}/
• Linux: ~/.cache/superpowers/browser-profiles/{name}/
• Windows: %LOCALAPPDATA%/superpowers/browser-profiles/{name}/

When to use separate profiles:

• Default profile ("superpowers-chrome"): General automation, shared sessions
• Agent-specific profiles: Isolate different agents' browser state
  • Example: browser-user agent uses "browser-user" profile
• Task-specific profiles: Testing with different user contexts
  • Example: "test-logged-in" vs "test-logged-out"

Profile data persists across:

• Chrome restarts
• Mode toggles (headless ↔ headed)
• System reboots (data is in cache directory)

To use a different profile:

1. Kill Chrome if running: await chromeLib.killChrome()
2. Set profile: {action: "set_profile", "payload": "my-profile"}
3. Start Chrome: Next navigate/action will use new profile

Quick Start Pattern

Navigate and extract:
{action: "navigate", payload: "https://example.com"}
{action: "await_element", selector: "h1"}
{action: "extract", payload: "text", selector: "h1"}

Common Patterns

Fill and Submit Form

{action: "navigate", payload: "https://example.com/login"}
{action: "await_element", selector: "input[name=email]"}
{action: "type", selector: "input[name=email]", payload: "user@example.com"}
{action: "type", selector: "input[name=password]", payload: "pass123\n"}
{action: "await_text", payload: "Welcome"}

The \n at the end of the password submits the form.

Multi-Tab Workflow

{action: "list_tabs"}
{action: "click", tab_index: 2, selector: "a.email"}
{action: "await_element", tab_index: 2, selector: ".content"}
{action: "extract", tab_index: 2, payload: "text", selector: ".amount"}

Dynamic Content

{action: "navigate", payload: "https://example.com"}
{action: "type", selector: "input[name=q]", payload: "query"}
{action: "click", selector: "button.search"}
{action: "await_element", selector: ".results"}
{action: "extract", payload: "text", selector: ".result-title"}

Get Link Attribute

{action: "navigate", payload: "https://example.com"}
{action: "await_element", selector: "a.download"}
{action: "attr", selector: "a.download", payload: "href"}

Execute JavaScript

{action: "eval", payload: "document.querySelectorAll('a').length"}
{action: "eval", payload: "Array.from(document.querySelectorAll('a')).map(a => a.href)"}

Resize Viewport (Responsive Testing)

Use eval to resize the browser window for testing responsive layouts:

{action: "eval", payload: "window.resizeTo(375, 812); 'Resized to mobile'"}
{action: "eval", payload: "window.resizeTo(768, 1024); 'Resized to tablet'"}
{action: "eval", payload: "window.resizeTo(1920, 1080); 'Resized to desktop'"}

Note: This resizes the window, not device emulation. It won't change:

• Device pixel ratio (retina displays)
• Touch events
• User-Agent string

For most responsive testing, window resize is sufficient.

Clear Cookies

Use eval to clear cookies accessible to JavaScript:

{action: "eval", payload: "document.cookie.split(';').forEach(c => { document.cookie = c.trim().split('=')[0] + '=;expires=Thu, 01 Jan 1970 00:00:00 GMT;path=/'; }); 'Cookies cleared'"}

Note: This clears cookies accessible to JavaScript. It won't clear:

• httpOnly cookies (server-side only)
• Cookies from other domains

For most logout/reset scenarios, this is sufficient.

Scroll Page

{action: "eval", payload: "window.scrollTo(0, document.body.scrollHeight); 'Scrolled to bottom'"}
{action: "eval", payload: "window.scrollTo(0, 0); 'Scrolled to top'"}
{action: "eval", payload: "document.querySelector('.target').scrollIntoView(); 'Scrolled to element'"}

Tips

Always wait before interaction: Don't click or fill immediately after navigate - pages need time to load.

// BAD - might fail if page slow
{action: "navigate", payload: "https://example.com"}
{action: "click", selector: "button"}  // May fail!

// GOOD - wait first
{action: "navigate", payload: "https://example.com"}
{action: "await_element", selector: "button"}
{action: "click", selector: "button"}

Use specific selectors: Avoid generic selectors that match multiple elements.

// BAD - matches first button
{action: "click", selector: "button"}

// GOOD - specific
{action: "click", selector: "button[type=submit]"}
{action: "click", selector: "#login-button"}

Submit forms with \n: Append newline to text to submit forms automatically.

{action: "type", selector: "#search", payload: "query\n"}

Check content first: Extract page content to verify selectors before building workflow.

{action: "extract", payload: "html"}

Troubleshooting

Element not found:

• Use await_element before interaction
• Verify selector with extract action using 'html' format

Timeout errors:

• Increase timeout: {timeout: 30000} for slow pages
• Wait for specific element instead of text

Tab index out of range:

• Use list_tabs to get current indices
• Tab indices change when tabs close

eval returns [object Object]:

• Use JSON.stringify() for complex objects: {action: "eval", payload: "JSON.stringify({name: 'test'})"}
• For async functions: {action: "eval", payload: "JSON.stringify(await yourAsyncFunction())"}

Test Automation (Advanced)

When building test automation, you have two approaches:

Approach 1: use_browser MCP (Simple Tests)

Best for: Single-step tests, direct Claude control during conversation

json
1{"action": "navigate", "payload": "https://app.com"}
2{"action": "click", "selector": "#test-button"}
3{"action": "eval", "payload": "JSON.stringify({passed: document.querySelector('.success') !== null})"}

Approach 2: chrome-ws CLI (Complex Tests)

Best for: Multi-step test suites, standalone automation scripts

Key insight: chrome-ws is the reference implementation showing proper Chrome DevTools Protocol usage. When use_browser doesn't work as expected, examine how chrome-ws handles the same operation.

bash
1# Example: Automated form testing
2./chrome-ws navigate 0 "https://app.com/form"
3./chrome-ws fill 0 "#email" "test@example.com"
4./chrome-ws click 0 "button[type=submit]"
5./chrome-ws wait-text 0 "Success"

When use_browser Fails

1. Check chrome-ws source code - It shows the correct CDP pattern
2. Use chrome-ws to verify - Test the same operation via CLI
3. Adapt the pattern - Apply the working CDP approach to use_browser

Common Test Automation Patterns

• Form validation: Fill forms, check error states
• UI state testing: Click elements, verify DOM changes
• Performance testing: Measure load times, capture metrics
• Screenshot comparison: Capture before/after states

Advanced Usage

For command-line usage outside Claude Code, see COMMANDLINE-USAGE.md.

For detailed examples, see EXAMPLES.md.

Protocol Reference

Full CDP documentation: https://chromedevtools.github.io/devtools-protocol/